Saturday, February 20, 2016

Building WiNode 5 - Part 1

Bare Board, 2 layer, 50mm x 50mm

Two weeks ago, you may remember I finished the pcb layout for a new microcontroller board - WiNode 5  - based on my 50 x 50mm standard board footprint.

Minimum Build.

With mcu, reset and crystal fitted, the board runs "Blink"code

For this I suggest fitting the ATmega1284 SMT package, the 16MHz crystal and its two 22pF capacitors C14 and C15.

Also the 10K reset resistor R1 and the FTDI 6way right-angled header JP1.

A 3.3V  MCP1702 regulator should be fitted in position IC4 along with C2, C4 and C5 its input and output capacitors.

Fit the four 100nF decoupling capacitors around the main microcontroller, C3, C7, C12 and C19.

The 3x2 pin ICSP programming header JP6 should also be fitted.

For LED output fit green LED1 and its 100R series resistor R10.

With this minimum build you may power the board from the FTDI cable and now program the bootloader using ICSP.  If this is successful, loading the blinky sketch should run and the LED should flash.

Now we add the USB chip IC7 (CH340G) the USB connector and the 12MHz USB crystal. Add the 22pf capacitors C18 and C20 and the 100nF decoupling capacitor C20.

Fit capacitors C8, C9  and resistor R2 to provide a filtered AVCC supply.

Add the RFM69 Wireless, the USB and the ESP-01 WiFi

The RFM69 wireless module and the ESP-01 WiFi connector and module can be added at this stage.

Finally - fit the four female shield mounting headers.

Fit the "Arduino" style female socket strips

These allow complete shields to be added, or small modules like the accelerometer module - which is powered by and connected to the Analogue Input port

With axdl 335 Accelerometer module fitted

Programming and Firmware

The Optiboot loader and Arduino "board"  files for this project are located at the Mighty1284 Github repository - with more information about the ATmega1284P implentation of Arduino here.

With the new 1284 board files loaded into the hardware directory of the Arduino IDE, you are now ready to program the Optiboot loader into some chips.

Having got the basics of the board in place, and proven that all was working so far, it was at a stage where it could be left  and I could get some sleep.

The final construction stages were to populate the boost converter, fit the FRAM (or SRAM) IC and fit the micro SDcard socket to the underside of the board.

WiNode 5 virtually complete - topside view
Above - the boost converter components, IC, 5 resistors, 2 capacitors and an inductor are added to the lower right corner of the board.

Just above the mcu is the SOIC-8 FRAM IC.

The microSD card socket is added to the underside of the pcb.

And a final word from our sponsors..... Ragworm provided additional boards at no extra charge and couriered them over in time for some weekend fun, as my job is putting the first few boards together.

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