This is a work in progress - have a look later for any updates
Introduction
Earlier this year I bought a Papilio Duo FPGA board from Gadget Factory. It has the combination of a FPGA and Arduino on the same pcb.
This board uses a Xilinx Spartan-6 closely connected to a 2Mbyte SRAM. This combination allows the FPGA to be used for generating VGA video - currently with a resolution of 800 x 600 pixels at 60Hz.
The killer feature of the Papilio Duo is that it will support the ZPUino - a 100MHz soft core which can be programmed using the Arduino IDE. This allows fairly rapid development of Arduino sketches - with the advantage of a fully accessible RAM block which can be used for frame buffers or other data storage.
In addition, the ZPUino will run the Adafruit GFX Graphics library. This is a generic graphics library for a number of different display types. When used with the ZPUino VGA it allows RGB 5:6:5 data for the 800 x 600 display. It has basic pixel plotting, line and circle drawing and fill commands - as well as various fonts and colours for on-screen text.
The ZPUino is fast enough to update the video buffer in about 1 second - this is fast enough for displaying captured video stills.
The combination of the above components creates a very basic but accessible Imaging Platform - which can be rapidly coded to perform. Whilst at first glance it might appear to be 25 year retro-step backwards in terms of computer graphics capailities, it offers an easy hackable platform, without all the constraints of a modern PC or operating system.
A Blast From the Past
30 years ago, in 1985, as my university final year project, I built up some hardware to allow the images from a scanning electron microscope (SEM) to be captured on an early x86 PC. Years later, a friend of mine who is a member of the Open Source Hardware Users Group, OSHUG, has acquired second hand, a scanning electron microscope dating from that era.
The SEM in question is a Cambridge Instruments Stereoscan 250 dating from 1985. It is in good condition, but lacks any means to capture images digitally, so is an ideal candidate to upgrade with a vision system - loosely based on my degree dissertation.
Of course, digital electronics has moved forwards inexorably since 1995, both in terms of speed of operation and RAM density - such that hardware costs in real terms is less than 100th of the price it was 30 years ago.
This makes it extremely viable to produce a complete imaging system using readily available open source hardware.
Some Design Aims and Objectives
Fundamentally this should be an open hardware project - reproducible by anyone using off the shelf hardware.
It will have an educational theme - allowing the user the experience of video systems, FPGAs and modern embedded mirocontrollers.
It will be extendable, and hopefully portable to other hardware - for example Raspberry Pi.
Some Specs
The SEM has an absolute scanning resolution of about 4096 x 4096 8 bit monochrome pixels. A full high-res image would therefore occupy 16MB of storage.
This resolution is not displayable on any monitor, so the compromise is to allow a smaller window view into the larger scanned field of view.
512x512 pixels is a convenient size for the available VGA system, so it would be possible to display a small window of just 1/64th of the whole field. When displayed on a 800 x 600 VGA monitor - this would allow adequate space around the image for text buttons, controls and tool icons.
It would be possible to extend this window to either (720x576) for 4:3 broadcast TV, or 800x600 for full screen display.
Sunday, August 23, 2015
Saturday, August 22, 2015
Adventures in ARM Land Part 3 - What Next?
A series of blog posts about working with 32 bit ARM microcontrollers
See Part 1 "Surveying the Territory"
and Part 2 "Establishing Base Camp"
Whilst you are waiting for Part 3 - here's some nice bedtime reading
The STM32F ARM M4F Peripherals Explained - in 320 easy slides
In Part 2, I explained how in a typical STM32 device there might be as many as 30 on chip peripherals that require configuring before they can be used. I also stated that for convenience - and to improve code clarity, that the peripheral configuration functions were grouped together in a module which I call periph_config.c.
In this post, I will try to illustrate how a series of re-usable functions, can be utilised to create a simple working environment for code development.
This idea has been heavily borrowed from Arduino Wiring - in an attempt to create a simpler coding environment, where perhaps STM32 Arduino or mbed is not available.
These functions should provide the following:
1. Basic Input and Output using GPIO
2. PWM
3. Analogue to Digital Conversion
4. Digital to Analogue Conversion
5. Millisecond timing, uS and mS delays
6. Serial Input and Output
7. A simple serial command interpreter framework
8. Triggering of events using external interrupts.
1. Basic GPIO
digitalRead(pin)
digitalWrite(pin)
2. PWM
3. 12 bit ADC
Read_ADC_12()
4. DACs
analogWrite(channel, value)
5. Millisecond Timing
delaymS()
delayuS()
6. Serial Input and Output
putchar
print_num
See Part 1 "Surveying the Territory"
and Part 2 "Establishing Base Camp"
Whilst you are waiting for Part 3 - here's some nice bedtime reading
The STM32F ARM M4F Peripherals Explained - in 320 easy slides
In Part 2, I explained how in a typical STM32 device there might be as many as 30 on chip peripherals that require configuring before they can be used. I also stated that for convenience - and to improve code clarity, that the peripheral configuration functions were grouped together in a module which I call periph_config.c.
In this post, I will try to illustrate how a series of re-usable functions, can be utilised to create a simple working environment for code development.
This idea has been heavily borrowed from Arduino Wiring - in an attempt to create a simpler coding environment, where perhaps STM32 Arduino or mbed is not available.
These functions should provide the following:
1. Basic Input and Output using GPIO
2. PWM
3. Analogue to Digital Conversion
4. Digital to Analogue Conversion
5. Millisecond timing, uS and mS delays
6. Serial Input and Output
7. A simple serial command interpreter framework
8. Triggering of events using external interrupts.
1. Basic GPIO
digitalRead(pin)
digitalWrite(pin)
2. PWM
3. 12 bit ADC
Read_ADC_12()
4. DACs
analogWrite(channel, value)
5. Millisecond Timing
delaymS()
delayuS()
6. Serial Input and Output
putchar
print_num
Adventures in ARM Land - Part 2 - Establishing Base Camp
Introduction
In part 1, I introduced a range of commercially available development boards which would allow the newcomer to get started with 32bit ARM microcontrollers - specifically the STM32Fxxx range from ST Microelectronics.
I also highlighted a list of software tools which allow the user to develop code for these boards, from othe traditional compiler IDE, free GCC based such as CooCox CoIDE, to newer tools, such as online compilers, mbed, Espruino and simpler IDEs aimed at the newcomer, such as Arduino STM32.
There is a lot of choice available, both in terms of the hardware boards and the programming tools. It's a case of knowing what's out there - so you can choose a combination that suits your application and your programming experience.
These ARM boards fill the middle ground between Arduino and Raspberry Pi. Whilst many times more powerful than the original Arduino, they lack the GHz speed and the Linux operating system of the Raspberry Pi. Nevertheless, this gives them baremetal flexability and means that they are ideal for standalone, high speed, battery powered applications - and complement the capabilities of the Raspberry Pi.
Getting Started.
Here are some options:
Newcomer
1. Arduino STM32
If you have previously worked with Arduino, but are looking for more of a challenge or a faster microcontroller, then the transition may be made quite easily by using Arduino STM32. This is a community led project that upgrades the Arduino IDE toolchain so that it can be used to program the STM32 with "Arduino code". A sketch written for Arduino may be compiled and uploaded onto a board fitted with a STM32F103. All programming is done within the same familiar Arduino IDE.
The STM32F103 is a 72MHz microcontroller available with a range of different flash and RAM size options - all of which exceed the size of the Arduino MEGA. In comparative, standard Benchmark tests, the STM32F103 will execute code at between 4 and 7 times the speed of the Arduino mega.
However it's real advantage is the rich mix of peripherals that come with the '103.
On chip USB
12 bit ADCs
12 bit DACs
Multiple USARTs
Multiple I2C and SPI interfaces
Greater code and RAM size - for larger applications
Arduino STM32 has been tailored to suit the STM32F103 series of M3 microcontrollers - and is now a mature implementation, however it is now starting to support the M4 processors such as the '303 and '407.
2. mbed
mbed is an online compiler tool that supports ARM hardware from multiple vendors. It has comprehensive code libraries to support the various peripherals, and allows easy porting from one vendor's ARM devices to another. In terms of the STMF32 family it supports a range of Nucleo, Discovery and 3rd party boards.
From a programming point of view, mbed is similar to Arduino, but has a much cleaner, professional looking IDE. The code is compiled by an online compiler, where the binary file is generated and then forwarded to the browser as a download file. The bin file is then dragged onto the icon - which represents the target board as a flash drive, and the code is loaded and executed. It's fairly straightforward and easy to use. There are many code examples and templates to get you started and an online reference of what the various library functions do. As the compiler is cloud based, the application works on all platforms Windows, MAC and Linux.
If you want to progress away from the Arduino environment, and try out a wide range of powerful processors from many vendors - then mbed is probably the best way forwards.
3. Javascript for Microcontrollers
This is an interesting development by Espruino. It allows a few of the STM32Fxxx family of microcontrollers to be programmed using Javascript - generated from an online script editor.
Espruino produce a couple of their own target boards, the Espruino and the Pico, additionally the Javascript can be run on a variety of 3rd party boards including the Discovery F3, F4 and Nucleo 401 boards.
It is backed up with a comprehensive range of "modules" - essentially libraries that support common hardware devices - such as colour LCDs, WiFi, Ethernet controllers, and all the real world hardware that turns the microcontroller into a proper application. The list of hardware modules may be found here.
Intermediate
4. CooCox CoIDE
If you are an intermediate programmer, familiar with traditional IDE toolchains, then CoIDE from CooCox offers a free toolchain based on GCC and Eclipse. It takes a little bit of getting used to CooCox, but it forms a useful framework for developing code projects. CooCox supports ARM microcontrollers and boards from a range of vendors, and has built in extensions for flash programming the device.
5. Keil MDK-ARM Microcontroller Development Kit based on uVision 5
This is a full featured commercial tool chain from one of the principal compiler vendors. As a commercial product, it is likely to be too expensive for the amateur or hobbyist, however it is also available as a free to use, code size limited (32K) evaluation copy.
When I came to develop code on the STM32F746 BoB target board - this was the only available option. Shortly, there will be an option from mbed to support the STM32F746 Discovery platform.
Peripheral Vision
Having chosen your board, and your preferred toolchain, it's then a case of following some simple code examples in order to start exercising the hardware and peripherals. This where it starts to get a little complicated, primarily because a 32bit ARM microcontroller is a very complex piece of silicon.
The ARM core communicates with all of the on-chip peripherals via a vast array of memory mapped registers. For example a UART will have a Transmit register and a Receive register and a Status register. All of the on-chip peripherals will have several registers controlling their operation. Unlike an 8-bit processor, it's very difficult to remember what all these registers are, so ST Microelectronics provides a library of helper functions, called the Standard Peripheral Library. They do this for each of the microcontrollers in the various STM32 families. Very often the peripheral registers are given the same name from device to device - but that is not always the case. You might get code running perfectly well on a STM32F407, and then find that who ever wrote the Standard Peripheral Library for the STM32F303, used a different set of incompatible register names - doh. This is what keeps you on your toes with ARM baremetal programming.
Fortunately there is a Reference Manual for every processor, which gives all of the register names and usually code examples - you just have to keep reading, or finding specific code examples online to help you.
HAL
The Standard Peripheral Libraries are the first layer of hardware abstraction offered on the STM32 parts. About 18 months ago, STM moved towards a new system STM32 Cube. This replaced the standard peripheral libraries with a new Hardware Abstraction Layer - called HAL. HAL is designed to improve code portability and allow access to complex library resources - but if you are new to it, it is quite a challenging concept to take on board. HAL will be the subject of a future post - once I feel competent enough to describe it in detail.
Arduino removes the complexity of the underlying hardware with a series of common C++ functions, provided by their "Wiring" functions. This is also a hardware abstraction layer, which makes coding advanced hardware interactivity a lot easier for the newcomer. Arduino STM32 makes use of this "wiring" layer, to provide an Arduino-like programming environment for the STM32F103 range of processors.
Establishing a Base Camp
Every programmer, when faced with a new device, quickly wants to establish some familiar territory prior to starting the main task of coding. Having Arduino or mbed as a lingua franca is one good way - but what if your particular choice of processor is not yet supported by these?
Most of my coding is done using CooCox CoIDE - so within this environment, I wanted to establish a convenient framework to allow applications to be more easily developed.
The STM32Fxxx range of microcontrollers have a vast range of onchip peripherals. To use these effectively they first have to be configured and then enabled prior to use. To keep track of all the peripheral code, I tend to keep it in a separate module from the main code.
To illustrate the quantity of peripherals in a typical STM32F M4 application
8 to 10 Timers for frequency generation, PWM, quadrature decoding etc
4 USARTs
4 ADCs
2 DACs
3 SPI
2 I2C
Up to 80 GPIO lines
DMA
RTC
etc etc
Each of these peripherals needs a block of code to configure it - so the peripheral configuration module might have 30 such blocks of code and run to some 1500 lines.
Fortunately once this code has been written, it is relatively simple to maintain and modify. It is relatively easy to move from one STM32Fxxx family member to another.
To avoid the confusion and complexity of a modern coding project - especially handling the peripheral configuration, I developed a strategy, that would help organise the code, and one that would allow ease of porting to other processors, when they came available. I started with just two code modules to start with:
main.c
periph_config.c
main.c - as it's name suggest is where you put your main loop and application code
periph_config.c is where you put all the hardware specific, peripheral initialisation functions.
In this way, as and when you needed to add a new peripheral, it could just be added to the functions contained in periph_config.c
For example, my application requires a serial interface to a PC. So within periph_config.c, I write the function that configures USART1, in terms of baudrate, start bits, stop bits, parity etc.
void USART1_Config(void)
{
// Put the USART1 initialisation code here
}
As the application grew and I needed to configure the remaining 3 USARTS, I just had to add their configuration code to periph_config.c - for example
void USART2_Config(void)
{
// Put the USART2 initialisation code here
}
void USART3_Config(void)
{
// Put the USART3 initialisation code here
}
This process was repeated for the remaining peripherals, ADCs, DACs, I2C, SPI, GPIO, DMA etc. If a new peripheral was needed or an existing one modified - I just had to edit periph_config.c.
The next thing was to make sure that all of the right peripherals were initialised at the start of my main code. To do this I wrote an Init() function:
void Init(void)
{
USART1_Config();
USART2_Config();
USART3_Config();
// and so on for all the other peripherals.........
}
Borrowing from the SetUp() and Loop() concept from Arduino
main()
{
Init(); // All of the peripheral initialisation code is executed once here
while(1)
{
// Put you main loop code within this while loop
}
} // end of main
// Private functions used within main are placed here
Using this simple method, I had a coding environment quite similar to what I was familiar with in Arduino.
Next Time
In the next part, I will look at some of the functions which help build up a simple application.
In part 1, I introduced a range of commercially available development boards which would allow the newcomer to get started with 32bit ARM microcontrollers - specifically the STM32Fxxx range from ST Microelectronics.
I also highlighted a list of software tools which allow the user to develop code for these boards, from othe traditional compiler IDE, free GCC based such as CooCox CoIDE, to newer tools, such as online compilers, mbed, Espruino and simpler IDEs aimed at the newcomer, such as Arduino STM32.
There is a lot of choice available, both in terms of the hardware boards and the programming tools. It's a case of knowing what's out there - so you can choose a combination that suits your application and your programming experience.
These ARM boards fill the middle ground between Arduino and Raspberry Pi. Whilst many times more powerful than the original Arduino, they lack the GHz speed and the Linux operating system of the Raspberry Pi. Nevertheless, this gives them baremetal flexability and means that they are ideal for standalone, high speed, battery powered applications - and complement the capabilities of the Raspberry Pi.
Getting Started.
Here are some options:
Newcomer
1. Arduino STM32
If you have previously worked with Arduino, but are looking for more of a challenge or a faster microcontroller, then the transition may be made quite easily by using Arduino STM32. This is a community led project that upgrades the Arduino IDE toolchain so that it can be used to program the STM32 with "Arduino code". A sketch written for Arduino may be compiled and uploaded onto a board fitted with a STM32F103. All programming is done within the same familiar Arduino IDE.
The STM32F103 is a 72MHz microcontroller available with a range of different flash and RAM size options - all of which exceed the size of the Arduino MEGA. In comparative, standard Benchmark tests, the STM32F103 will execute code at between 4 and 7 times the speed of the Arduino mega.
However it's real advantage is the rich mix of peripherals that come with the '103.
On chip USB
12 bit ADCs
12 bit DACs
Multiple USARTs
Multiple I2C and SPI interfaces
Greater code and RAM size - for larger applications
Arduino STM32 has been tailored to suit the STM32F103 series of M3 microcontrollers - and is now a mature implementation, however it is now starting to support the M4 processors such as the '303 and '407.
2. mbed
mbed is an online compiler tool that supports ARM hardware from multiple vendors. It has comprehensive code libraries to support the various peripherals, and allows easy porting from one vendor's ARM devices to another. In terms of the STMF32 family it supports a range of Nucleo, Discovery and 3rd party boards.
From a programming point of view, mbed is similar to Arduino, but has a much cleaner, professional looking IDE. The code is compiled by an online compiler, where the binary file is generated and then forwarded to the browser as a download file. The bin file is then dragged onto the icon - which represents the target board as a flash drive, and the code is loaded and executed. It's fairly straightforward and easy to use. There are many code examples and templates to get you started and an online reference of what the various library functions do. As the compiler is cloud based, the application works on all platforms Windows, MAC and Linux.
If you want to progress away from the Arduino environment, and try out a wide range of powerful processors from many vendors - then mbed is probably the best way forwards.
3. Javascript for Microcontrollers
This is an interesting development by Espruino. It allows a few of the STM32Fxxx family of microcontrollers to be programmed using Javascript - generated from an online script editor.
Espruino produce a couple of their own target boards, the Espruino and the Pico, additionally the Javascript can be run on a variety of 3rd party boards including the Discovery F3, F4 and Nucleo 401 boards.
It is backed up with a comprehensive range of "modules" - essentially libraries that support common hardware devices - such as colour LCDs, WiFi, Ethernet controllers, and all the real world hardware that turns the microcontroller into a proper application. The list of hardware modules may be found here.
Intermediate
4. CooCox CoIDE
If you are an intermediate programmer, familiar with traditional IDE toolchains, then CoIDE from CooCox offers a free toolchain based on GCC and Eclipse. It takes a little bit of getting used to CooCox, but it forms a useful framework for developing code projects. CooCox supports ARM microcontrollers and boards from a range of vendors, and has built in extensions for flash programming the device.
5. Keil MDK-ARM Microcontroller Development Kit based on uVision 5
This is a full featured commercial tool chain from one of the principal compiler vendors. As a commercial product, it is likely to be too expensive for the amateur or hobbyist, however it is also available as a free to use, code size limited (32K) evaluation copy.
When I came to develop code on the STM32F746 BoB target board - this was the only available option. Shortly, there will be an option from mbed to support the STM32F746 Discovery platform.
Peripheral Vision
Having chosen your board, and your preferred toolchain, it's then a case of following some simple code examples in order to start exercising the hardware and peripherals. This where it starts to get a little complicated, primarily because a 32bit ARM microcontroller is a very complex piece of silicon.
The ARM core communicates with all of the on-chip peripherals via a vast array of memory mapped registers. For example a UART will have a Transmit register and a Receive register and a Status register. All of the on-chip peripherals will have several registers controlling their operation. Unlike an 8-bit processor, it's very difficult to remember what all these registers are, so ST Microelectronics provides a library of helper functions, called the Standard Peripheral Library. They do this for each of the microcontrollers in the various STM32 families. Very often the peripheral registers are given the same name from device to device - but that is not always the case. You might get code running perfectly well on a STM32F407, and then find that who ever wrote the Standard Peripheral Library for the STM32F303, used a different set of incompatible register names - doh. This is what keeps you on your toes with ARM baremetal programming.
Fortunately there is a Reference Manual for every processor, which gives all of the register names and usually code examples - you just have to keep reading, or finding specific code examples online to help you.
HAL
The Standard Peripheral Libraries are the first layer of hardware abstraction offered on the STM32 parts. About 18 months ago, STM moved towards a new system STM32 Cube. This replaced the standard peripheral libraries with a new Hardware Abstraction Layer - called HAL. HAL is designed to improve code portability and allow access to complex library resources - but if you are new to it, it is quite a challenging concept to take on board. HAL will be the subject of a future post - once I feel competent enough to describe it in detail.
Arduino removes the complexity of the underlying hardware with a series of common C++ functions, provided by their "Wiring" functions. This is also a hardware abstraction layer, which makes coding advanced hardware interactivity a lot easier for the newcomer. Arduino STM32 makes use of this "wiring" layer, to provide an Arduino-like programming environment for the STM32F103 range of processors.
Establishing a Base Camp
Every programmer, when faced with a new device, quickly wants to establish some familiar territory prior to starting the main task of coding. Having Arduino or mbed as a lingua franca is one good way - but what if your particular choice of processor is not yet supported by these?
Most of my coding is done using CooCox CoIDE - so within this environment, I wanted to establish a convenient framework to allow applications to be more easily developed.
The STM32Fxxx range of microcontrollers have a vast range of onchip peripherals. To use these effectively they first have to be configured and then enabled prior to use. To keep track of all the peripheral code, I tend to keep it in a separate module from the main code.
To illustrate the quantity of peripherals in a typical STM32F M4 application
8 to 10 Timers for frequency generation, PWM, quadrature decoding etc
4 USARTs
4 ADCs
2 DACs
3 SPI
2 I2C
Up to 80 GPIO lines
DMA
RTC
etc etc
Each of these peripherals needs a block of code to configure it - so the peripheral configuration module might have 30 such blocks of code and run to some 1500 lines.
Fortunately once this code has been written, it is relatively simple to maintain and modify. It is relatively easy to move from one STM32Fxxx family member to another.
To avoid the confusion and complexity of a modern coding project - especially handling the peripheral configuration, I developed a strategy, that would help organise the code, and one that would allow ease of porting to other processors, when they came available. I started with just two code modules to start with:
main.c
periph_config.c
main.c - as it's name suggest is where you put your main loop and application code
periph_config.c is where you put all the hardware specific, peripheral initialisation functions.
In this way, as and when you needed to add a new peripheral, it could just be added to the functions contained in periph_config.c
For example, my application requires a serial interface to a PC. So within periph_config.c, I write the function that configures USART1, in terms of baudrate, start bits, stop bits, parity etc.
void USART1_Config(void)
{
// Put the USART1 initialisation code here
}
As the application grew and I needed to configure the remaining 3 USARTS, I just had to add their configuration code to periph_config.c - for example
void USART2_Config(void)
{
// Put the USART2 initialisation code here
}
void USART3_Config(void)
{
// Put the USART3 initialisation code here
}
This process was repeated for the remaining peripherals, ADCs, DACs, I2C, SPI, GPIO, DMA etc. If a new peripheral was needed or an existing one modified - I just had to edit periph_config.c.
The next thing was to make sure that all of the right peripherals were initialised at the start of my main code. To do this I wrote an Init() function:
void Init(void)
{
USART1_Config();
USART2_Config();
USART3_Config();
// and so on for all the other peripherals.........
}
Borrowing from the SetUp() and Loop() concept from Arduino
main()
{
Init(); // All of the peripheral initialisation code is executed once here
while(1)
{
// Put you main loop code within this while loop
}
} // end of main
// Private functions used within main are placed here
Using this simple method, I had a coding environment quite similar to what I was familiar with in Arduino.
Next Time
In the next part, I will look at some of the functions which help build up a simple application.
Adventures in ARM Land - Part 1 - Surveying the Territory
Introduction
This post is the first of a series of three (or more), intended to introduce the newcomer to the world of 32bit ARM processors, based on my past experiences. Whilst not a tutorial with code examples (these are available elsewhere online) it is hoped that others will be inspired to follow a similar journey.
In this post I introduce some low cost commercially available development boards, and the range of software tools currently available with which to program them.
I also showcase three of my own open source hardware designs, to illustrate that these microcontroller pcbs are not beyond the realm of hobbyist pcb design and construction.
On the Job Tinkering with ARM Chips
In November 2013, I had the opportunity to explore a new range of 32 bit microcontrollers as part of a development to upgrade our product range at work.
Since then, I have been working both professionally and on a hobby basis with the series of ARM Cortex M microcontrollers from ST Microelectronics.
I was initially attracted to this series of devices because of their rich set of peripherals and resources, low cost development boards and that there was a rapidly growing User Community.
Having put a significant amount of time into familiarising myself with this new family of processors, I have found that they are relatively easy to use, and that it is fairly straightforward to move between different members of the family - depending on your application.
There are a very wide range of target boards available - some starting at less than $5 (from China). Additionally, ST Microelectronics produces it's own range of very low cost target boards - to get you quickly started on your application.
Not an Arduino and not a Pi
The STM32Fxxx family of 32bit microcontrollers are available with clock speeds between 72MHz and 216MHz. This places them at about 4 to 16 times faster than an Arduino based on the 16MHz ATmega328. In addition, their 32bit wordsize, larger flash memory and RAM allows more complex applications to be run. The STM32F Cortex M4 has a floating point unit (FPU) capable of executing single cycle multiplication, hardware divide and some DSP instructions.
Whilst faster than the original Arduino (and Due), they cannot compete in speed with the 1GHz quad core Raspberry Pi 2. However, as they were designed for the embedded microcontroller market, they have several peripherals that the Pi lacks - such as 12bit ADCs and DACs. Also, as they are unlikely to ever support Linux, it means that your application is not constrained by the operating system, giving you full access to the timing - making them ideal for Real Time Control applications.
Finally, the processor has a number of power saving modes, and even flat out will only consume between 50 and 100mA. This makes them ideal for hand held, battery operated applications.
Maple Mini (Chinese Copy)
The Maple Mini was one of the first hobbyist boards to use the STM32F103 - originally produced by Leaf Labs in Canada. Leaf Labs no longer support this board, but it has been widely copied in China and is available for as little as $5. The example above is a 40 pin DIL format making it ideal to fit into a prototyping breadboard. Leaf Labs derived their own version of the Arduino IDE - and now through a community project, their code has now been adopted and updated by Arduino STM32 - allowing you to program these little boards directly from the Arduino language. Ideal for beginners.
Nucleo Boards
These are produced by ST Microelectronics and offer a very low cost way to get started with ARM and mbed programming. The upper part of the pcb is a "detachable" ST Link V2 flash programmer - alone worth about £20. The programmer section can be used with a 6 way cable to program other STM32F ARM boards you may have.
The lower part of the pcb has both Arduino footprint connectors - allowing the use of some Arduino shields, but additionally the STM "Morpho" dual row connectors, allowing access to all of the I/O pins.
This ability to change between processors has been exploited to it's full potential with the range of ST Nucleo development boards - a small, low cost, "Arduino like" platform, with built in flash programmer, and the means to be programmed using the online mbed compiler. Each Nucleo board is fitted with a 64pin LQFP microcontroller which being virtually pin identical, allows you to choose which processor best suits your application.
A full list of Nucleo boards is described here - but notably here are the ones I have used
STM32F103 ARM Cortex M3 72MHz - a good general purpose microcontroller
STM32F303 ARM Cortex M4F 72MHz - Analogue SoC with 5MSPs ADC, PGA etc
STM32F373 ARM Cortex M4F 72MHz - 3 x 16bit SD ADCs
STM32F401 ARM Cortex M4F 84MHz - low power microcontroller
STM32F401 ARM Cortex M4F 100MHz - low power microcontroller
If you choose to develop code for these using the mbed platform, you can readily switch between target boards to assess which target is best for your application. For example, whilst all STM32Fxxx microcontrollers have multiple 12bit ADC and DAC channels, you will find that the STM32F303 has the highest speed ADC (5MSPs) but the STM32F373 offers in addition, 3 independent 16 bit ADCs - which is ideal for 3-phase energy measurements.
If however you are looking for a low power controller perhaps for extended battery operation, the STM32F401 and 411 are described as STM's "Dynamic Efficiency Line" and use a "Batch Acquisition Mode" BAM - a low power means of acquiring data from sensors, processing the data, then returning to a low power state.
Discovery Boards
STM also has a range of feature rich Discovery Boards - with additional hardware included on board to specifically highlight typical user applications. The top quarter of the pcb is the STM32F ST Link V2 flash programmer. All of the STM32F407 GPIO pins are broken out into the twin row connectors.
This Discovery F4 board is a powerful board - with a processing throughput approximately 15 times that of an Arduino. It has 80 GPIO lines and a rich set of peripherals making it idea for motor control and instrumentation systems.
These are available for the following microcontrollers (plus others)
STM32F303 - with on board compass and accelerometer sensors
STM32F407 - with accelerometer, audio sampling and playback
STM32F429 - with colour LCD
STM32F746 - with colour touchscreen LCD, Ethernet + camera, audio, + much, much more
My own ARM journey started with the Discovery F4, but I have evaluated the others above, for various applications, both at work and for play.
Software Tools
There is an ever increasing number of options available to allow you to program these microcontrollers - so far I have looked at the following:
1. A fully functioning tool suite from one of the major suppliers - very expensive
2. A code size limited tool chain - free to use for smaller applications
3. An online tool chain - for example mbed
4. Free to use IDE using open source GCC - Coocox CoIDE
5. Online Javascript - notably Espruino - offering JS to STM32xxx microcontrollers
6. Aruino_STM32 - a community based extension to Arduino allowing Arduino IDE coding for STM32F Cortex and M3 and M4.
Some of these are windows platform only. Some do not fully support certain microcontrollers - so for example, whilst I generaly use Coocox or mbed, I had to use a 32K code size limited version of Keil's uVision 5 in order to develop code for the STM32F746 Cortex M7.
Arduino STM32 is an interesting option for hobbyists, because it allows an easy transition from the AVR based Arduino platforms to much more powerful ones based on the STM32F103. Sketches written for the Arduino can be easily ported to ARM M3 and M4 based hardware. It also allows the Arduino community to break free from the limitations of the official Arduino platforms.
Some Hardware Notes
The STM32Fxxx range of microcontrollers are available in a range of package sizes from LQFP-48 upwards. The "leaded quad flat pack" package may be soldered by hand, if sufficient care is taken. This offers the options for enthusiasts to design their own pcbs - using EagleCAD or KiCAD etc.
Personally, I have designed pcbs to accept 48 pin, 64 pin and 100 pin parts using EagleCAD. Initially these were intended as Breakout Boards - so that I could access all the peripheral pins - without other hardware getting in the way. Later, these designs generally evolved into more application specific devices.
Three of my existing designs are intended for Open Sourcing:
1. ARMiGo - accepts a 48 pin LQFP, either STM32F103, STM32F303 or STM32F373 and makes its pins available on a 40 pin 0.6" DIL header - intended for breadboard prototyping.
2. Piano Forte - accepts a 64 pin LQFP, either STM32F103, STM32F303 or STM32F373 and makes its I/O available in an Arduino pin-out or as 2.1" wide SIL header format - that can be placed across 2 breadboards. Can also be plugged into a Raspberry Pi - and used as a PI-HAT compatible Analogue and Digital I/O board to augment the Pi.
3. BoB - A totally uncluttered breakout board for the 100 pin LQFP STM32F746. Breaks out the I/O of the STM32F746 into the 2x25 pin dual row headers as used on the Discovery F4. Allows the Cortex M7 to be evaluated as an 2X+ performance upgrade to the Cortex M4.
Availability
In the UK, STM32 Discovery and Nucleo boards may be obtained from
Farnell - business customers
CPC - hobbyists
RS Components
In the US
Newark
Digikey
Mouser
This post is the first of a series of three (or more), intended to introduce the newcomer to the world of 32bit ARM processors, based on my past experiences. Whilst not a tutorial with code examples (these are available elsewhere online) it is hoped that others will be inspired to follow a similar journey.
In this post I introduce some low cost commercially available development boards, and the range of software tools currently available with which to program them.
I also showcase three of my own open source hardware designs, to illustrate that these microcontroller pcbs are not beyond the realm of hobbyist pcb design and construction.
On the Job Tinkering with ARM Chips
In November 2013, I had the opportunity to explore a new range of 32 bit microcontrollers as part of a development to upgrade our product range at work.
Since then, I have been working both professionally and on a hobby basis with the series of ARM Cortex M microcontrollers from ST Microelectronics.
I was initially attracted to this series of devices because of their rich set of peripherals and resources, low cost development boards and that there was a rapidly growing User Community.
Having put a significant amount of time into familiarising myself with this new family of processors, I have found that they are relatively easy to use, and that it is fairly straightforward to move between different members of the family - depending on your application.
There are a very wide range of target boards available - some starting at less than $5 (from China). Additionally, ST Microelectronics produces it's own range of very low cost target boards - to get you quickly started on your application.
Not an Arduino and not a Pi
The STM32Fxxx family of 32bit microcontrollers are available with clock speeds between 72MHz and 216MHz. This places them at about 4 to 16 times faster than an Arduino based on the 16MHz ATmega328. In addition, their 32bit wordsize, larger flash memory and RAM allows more complex applications to be run. The STM32F Cortex M4 has a floating point unit (FPU) capable of executing single cycle multiplication, hardware divide and some DSP instructions.
Whilst faster than the original Arduino (and Due), they cannot compete in speed with the 1GHz quad core Raspberry Pi 2. However, as they were designed for the embedded microcontroller market, they have several peripherals that the Pi lacks - such as 12bit ADCs and DACs. Also, as they are unlikely to ever support Linux, it means that your application is not constrained by the operating system, giving you full access to the timing - making them ideal for Real Time Control applications.
Finally, the processor has a number of power saving modes, and even flat out will only consume between 50 and 100mA. This makes them ideal for hand held, battery operated applications.
Maple Mini (Chinese Copy)
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| A "Maple Mini" - a low cost STM32F103 board from China |
Nucleo Boards
These are produced by ST Microelectronics and offer a very low cost way to get started with ARM and mbed programming. The upper part of the pcb is a "detachable" ST Link V2 flash programmer - alone worth about £20. The programmer section can be used with a 6 way cable to program other STM32F ARM boards you may have.
The lower part of the pcb has both Arduino footprint connectors - allowing the use of some Arduino shields, but additionally the STM "Morpho" dual row connectors, allowing access to all of the I/O pins.
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| Nucleo-F103RB - about £8.50 from Farnell CPC |
This ability to change between processors has been exploited to it's full potential with the range of ST Nucleo development boards - a small, low cost, "Arduino like" platform, with built in flash programmer, and the means to be programmed using the online mbed compiler. Each Nucleo board is fitted with a 64pin LQFP microcontroller which being virtually pin identical, allows you to choose which processor best suits your application.
A full list of Nucleo boards is described here - but notably here are the ones I have used
STM32F103 ARM Cortex M3 72MHz - a good general purpose microcontroller
STM32F303 ARM Cortex M4F 72MHz - Analogue SoC with 5MSPs ADC, PGA etc
STM32F373 ARM Cortex M4F 72MHz - 3 x 16bit SD ADCs
STM32F401 ARM Cortex M4F 84MHz - low power microcontroller
STM32F401 ARM Cortex M4F 100MHz - low power microcontroller
If you choose to develop code for these using the mbed platform, you can readily switch between target boards to assess which target is best for your application. For example, whilst all STM32Fxxx microcontrollers have multiple 12bit ADC and DAC channels, you will find that the STM32F303 has the highest speed ADC (5MSPs) but the STM32F373 offers in addition, 3 independent 16 bit ADCs - which is ideal for 3-phase energy measurements.
If however you are looking for a low power controller perhaps for extended battery operation, the STM32F401 and 411 are described as STM's "Dynamic Efficiency Line" and use a "Batch Acquisition Mode" BAM - a low power means of acquiring data from sensors, processing the data, then returning to a low power state.
Discovery Boards
 |
| Discovery F4 - About £12.50 from Farnell |
STM also has a range of feature rich Discovery Boards - with additional hardware included on board to specifically highlight typical user applications. The top quarter of the pcb is the STM32F ST Link V2 flash programmer. All of the STM32F407 GPIO pins are broken out into the twin row connectors.
This Discovery F4 board is a powerful board - with a processing throughput approximately 15 times that of an Arduino. It has 80 GPIO lines and a rich set of peripherals making it idea for motor control and instrumentation systems.
These are available for the following microcontrollers (plus others)
STM32F303 - with on board compass and accelerometer sensors
STM32F407 - with accelerometer, audio sampling and playback
STM32F429 - with colour LCD
STM32F746 - with colour touchscreen LCD, Ethernet + camera, audio, + much, much more
My own ARM journey started with the Discovery F4, but I have evaluated the others above, for various applications, both at work and for play.
Software Tools
There is an ever increasing number of options available to allow you to program these microcontrollers - so far I have looked at the following:
1. A fully functioning tool suite from one of the major suppliers - very expensive
2. A code size limited tool chain - free to use for smaller applications
3. An online tool chain - for example mbed
4. Free to use IDE using open source GCC - Coocox CoIDE
5. Online Javascript - notably Espruino - offering JS to STM32xxx microcontrollers
6. Aruino_STM32 - a community based extension to Arduino allowing Arduino IDE coding for STM32F Cortex and M3 and M4.
Some of these are windows platform only. Some do not fully support certain microcontrollers - so for example, whilst I generaly use Coocox or mbed, I had to use a 32K code size limited version of Keil's uVision 5 in order to develop code for the STM32F746 Cortex M7.
Arduino STM32 is an interesting option for hobbyists, because it allows an easy transition from the AVR based Arduino platforms to much more powerful ones based on the STM32F103. Sketches written for the Arduino can be easily ported to ARM M3 and M4 based hardware. It also allows the Arduino community to break free from the limitations of the official Arduino platforms.
Some Hardware Notes
The STM32Fxxx range of microcontrollers are available in a range of package sizes from LQFP-48 upwards. The "leaded quad flat pack" package may be soldered by hand, if sufficient care is taken. This offers the options for enthusiasts to design their own pcbs - using EagleCAD or KiCAD etc.
Personally, I have designed pcbs to accept 48 pin, 64 pin and 100 pin parts using EagleCAD. Initially these were intended as Breakout Boards - so that I could access all the peripheral pins - without other hardware getting in the way. Later, these designs generally evolved into more application specific devices.
Three of my existing designs are intended for Open Sourcing:
1. ARMiGo - accepts a 48 pin LQFP, either STM32F103, STM32F303 or STM32F373 and makes its pins available on a 40 pin 0.6" DIL header - intended for breadboard prototyping.
2. Piano Forte - accepts a 64 pin LQFP, either STM32F103, STM32F303 or STM32F373 and makes its I/O available in an Arduino pin-out or as 2.1" wide SIL header format - that can be placed across 2 breadboards. Can also be plugged into a Raspberry Pi - and used as a PI-HAT compatible Analogue and Digital I/O board to augment the Pi.
3. BoB - A totally uncluttered breakout board for the 100 pin LQFP STM32F746. Breaks out the I/O of the STM32F746 into the 2x25 pin dual row headers as used on the Discovery F4. Allows the Cortex M7 to be evaluated as an 2X+ performance upgrade to the Cortex M4.
Availability
In the UK, STM32 Discovery and Nucleo boards may be obtained from
Farnell - business customers
CPC - hobbyists
RS Components
In the US
Newark
Digikey
Mouser
Sunday, August 09, 2015
Holiday Hacking - A Survivor's Guide
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| I'd forgotten I was packing so many platforms..... |
The idea being that with a minimum kit of parts, easily carried, and perhaps some online guide, that it would be possible to set up virtually anywhere and learn how to code, by practical experimentation.
At the end of July, I had travelled to Rhodes, armed with a few dev boards, a breadbord, some components and a netbook, which I considered to be the minimum I could get away with and yet do some serious hacking.
As it Stands....
Presently, there are two main physical computing platforms, Raspberry Pi and Arduino, which between them, probably covers 90% of all hack applications, however there are some newer arrivals, mostly 32bit ARM based platforms, that offer some interesting new middle ground to explore as the basis for hacking projects. These will we covered later.
 |
| The Lunchbox has landed.... |
BOB - an ARM M7 breakout board
A small bomb disguised as an EE Powerbar
Essential FTDI cable
Two breadboards
jumper wires
all served on small raft of wire- ended components.
A Minimum Solution.
You can do a lot with an Arduino, a USB cable and a laptop or netbook PC. To me I feel this offers a minimum solution that provides a basis for experimentation. However an Arduino on it's own, lacks any real interactivity - there's only so much that you can do with a single flashing LED. We need to add a few more bells and whistles.
The Arduino Experimenter's kit (this one from Adafruit - but lots of others to choose from) seems a close approximate to what is needed, as it provides Arduino, breadboard and a selection of components and jumper wires that allow a fair amount of experiments to be performed. Add to this a Netbook, with the latest Arduino IDE loaded, and you have a minimum portable package that can be taken on the road.
Add a couple of your favourite shields, and you have a compact playkit that will easily fit into a plastic sandwich box.
The Arduino however is now showing its age, and lacks a lot of user interactivity. A better package would be a Raspberry Pi and a Pibrella - which includes a bunch of LEDs, switch and small speaker. By connecting the Pi to the PC, either with a USB or network cable you have a hackable platform, with the netbook PC providing a workable screen and keyboard, for code development. This was the arrangement we used at a recent node-RED workshop, hosted by Dr. Andy Stanford Clark and Dr. Lucy Rogers.
The Pi on it's own also lacks any real user interaction - unless you have keyboard and screen attached, and it also requires quite a lot of current to operate. This means that you probably won't be able to power it off a netbook USB port, which means finding a mains adaptor or some sort of alternative supply. Fortunately there are now a number of LiPo battery solutions being made available for the Pi to greatly extend its portability. At a pinch, you might be able to power one for a couple of hours from a mobile phone charging pack.
Then there is the question of what components to take, for maximum interactivity. LEDs, both individual, such as for traffic light displays, or 7-segment or matrix are also good for creating visual effects. Simple rows of LEDs, driven individually from a port pin are good for chaser effects (Knight Rider) and bargraph displays.
Switches, sensors and sounders also allow for a lot of creative coding. Last week in Rhodes, I knocked up a simple thermometer using a thermistor, resistor and an Arduino, and soon I could tell that it was 32C in the shade. Adding a couple of 7 segment displays would have made for an interesting self contained project.
As technology becomes more sophisticated, it is natural that hackers want to explore its bounds. One idea might be a colour LCD touchscreen that provides the user interactivity. Products such as Gameduino and Gameduino2, allow a platform even as humble as an Arduino to host an arcade style game- with the processing grunt to handle the display provided by the Gameduino.
It's a question of personal choice, given a restriction of how much kit you can take, would you opt for low level hacking of hardware, or spend time writing higher level code for simple games?
Hanging On the Telephone.....
The other possibility is that a Smartphone could be used for interactivity. This is the route suggested by the recent Microbit platform promoted by the BBC. Whilst it provides a simple LED matrix and a couple of switches, it could readily be connected to a mobile phone that provides a simple coding interface. Additionally it is powered by a small ARM processor with on chip Bluetooth LE, so board to board, and board to phone communications are achievable. An accelerometer and magnetometer compass sensor is provided on board, so interacting to motion and direction is also an area to explore. PC connection is via a USB cable and the interface is a web browser.
The inclusion of BLE on board allows this platform to connect with both Android and iOS smartphones - BLE being the common accessible link.
Microbits provides sufficient interactivity for fun-based hacking, and its relatively low power consumption means that standalone, battery operation is possible. This opens out possibilities for free-roaming robots, controlled via BLE, or battery powered sensors, communicating back to a phone or laptop via BLE.
Hopefully with the 1 million Microbit roll-out distribution to Year 7 students in UK schools, then this will inspire a new generation to explore the new world of physical computer hacking.
The good news is that the manufacturers intend to make Microbits available to anyone who wants to buy them - after the initial BBC rollout to secondary schools.
As soon as we start to see some real information, and tech specs, circuit diagrams of Microbits, then the hack community can go to work on this new device. I really hope that it succeeds, and that these little hack-buddies don't just go straight to landfill.
It's early days - so time will tell.
New Horizons
Arduino is a great beginner's platform but is now in it's 10th year, and starting to show it's age. It can easily be hacked with parts on a breadboard or additional functionality on a shield. It is low power, and the IDE is self-contained and usable for even the inexperienced coder. However, so much more can be achieved by moving on to platforms based on 32bit ARM technology.
Raspberry Pi, being a considerably more powerful processor and GPU, allows for the hosting of operating systems and high level languages, with video and graphics. Now in it's fourth year, there are an increasing number of Pi HATs available, for user experimentation. The GPIO is not as robust as that of the Arduino - so you have to treat it with a little more respect- nobody enjoys fried Pi!
Other platforms are available, that cover some of the middle ground between Arduino and Pi. These are 32 bit ARM based platforms which in some cases can be programmed with a modified Arduino IDE. Alternatively some host, scripting languages, (the Espruino - which runs JavaScript) which allow reasonable high level code development. The mbed online compiler, is another solution, which allows you to code in a fairly friendly environment, provided that you have internet access. There are not many resorts in Europe where you can't find a cafe or bar with wifi access. mbed supports a wide range of ARM platforms, including microcontrollers from FreeScale and STMicroelectronics. The low cost (<£10) ST Nucleo platforms are not only Arduino shield compatible, but offer 5V tolerance on all but the ADC pins and a lot more grunt than the Arduino.
Smartphone interactivity, WiFi, BLE and touchscreen displays will further enhance what can be done with these small platforms, making them an attractive addition to any Hacker's survival kit.
The laptop or netbook is the centre of your hack environment. Make sure that you have preloaded it with all the software apps that you might need whilst away from base. Mine has the Arduino IDE, Termite- a terminal emulator, EagleCAD and CooCox COIDE - an IDE for ARM code development. Irfanview is also great for photo handling. With Open Office/Libre, and using your smartphone as a camera, you can achieve a surprising amount with minimum tools. This blog was written in Notepad++ whilst no wifi was available and then ported to my blog when I got to my favourite bar.
Powerful Solutions
Electronics doesn't work without power, and in the case of a laptop or netbook, you will be looking to recharge every few hours. Don't forget to pack the charger and the travel adaptor for whichever continent you are visiting.
Don't wait till you get to the airport where they will fleece you £7.79 for something you can buy in Poundland. Speaking of which, Poundland is also a good source for microUSB cables and ear-plugs - stock up whilst you are there for some emergency spares.
If your laptop battery is down to 10%, find a cafe or bar, and have a snack or a drink for an hour, having either cased the joint for power outlets - or asked the staff politely. It will cost you about 4 Euros (£3) but that is the cost of an opportunity charge. Don't forget to plug in at night, if you are staying in an apartment. If you are roughing it - consider the possibilities of a small solar charger - there are some good ones about the size of a Kindle, or some of the new power packs - used for topping up mobile phones. If you are seriously hacking - find a nice, cool place to work - with a mains outlet.
Packing it Up
Taking hacking supplies abroad presents few if any real problems. Provided that you are careful, there's not many things that you can't pack in a suitcase. Pack your boards and bits into a small box, and put them in your hold luggage. Any tools you carry, screwdrivers or cutters, should also go in hold luggage. Try to include any original packaging, so that if your cache of boards is investigated, it can be clearly seen that they are commercial products - and not an IED. Any wires or components should be put in plastic bags - clearly visible, and not at all bomb like. Take special care with any LiPo batteries you are carrying - make sure they are secure and cannot short to any metallic object.
A few days after I got to Rhodes, there was a news story concerning faulty smartphone rechargers - the PowerBar distributed by EE. A particular batch had proven to be faulty and had to be recalled, as about 1 in 100,000 had an overheat/explode tendency. That's my "faulty" PowerBar (green&yellow) at the centre of the sandwich box. I will be particularly careful when packing that back in my hold luggage - though the risk is miniscule.
It is very unlikely that your hold luggage will go through an extensive search - but don't take any chances. I know a girl hacker in the USA who walked into airport security with a bit of wearable technology, and was very close to being shot by nervous armed guards.
Laptops, netbooks and tablets present little security threat, and can readily be carried on as hand luggage. The Airbus I travelled on provided WiFi, and provided that the GSM phone functions are disabled in "Airplane Mode", most airlines will now accept WiFi, BLE and other 2.4GHz device communications for the majority of the flight.
If you are on holiday - don't forget to do the usual holiday things too, but often, once away from the usual work environment, your brain finds spare capacity to think of new ideas, that can be planned and put into action upon return.
For extra Geekiness....In the top photo - top row
STM32F4 Discovery - low cost STM32F407 ARM M4 Cortex based
WiNode - Arduino based with 433MHz wireless (one of mine)
ServoNode - Arduino based - designed by my firm's student intern - in his first week :)
ARMiGo - ARM M4 Cortex designed for breadboard friendliness (one of mine)
Centre
BOB - a breakout board for the STMF7 (one of mine - making international debut)
Nanode - Arduino based - a friendly hackhorse I designed in 2011
Bottom Row - hatrick
PianoForte - an ARM M4 Cortex based I/O Pi HAT format supercharger for the Raspberry Pi WiFi/BLE/RFM69 connectivity - one of my DIYs.