tag:blogger.com,1999:blog-16736699.post5973879319511939068..comments2024-02-01T16:41:23.163+00:00Comments on Sustainable Suburbia: Nano Tweets - It's an EnigmaKen Boakhttp://www.blogger.com/profile/01168707285621954181noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-16736699.post-13631437619725441272011-04-06T08:00:54.523+01:002011-04-06T08:00:54.523+01:00Details of the Currentcost XML protocol can be fou...Details of the Currentcost XML protocol can be found here:<br /><br />http://www.currentcost.com/cc128/xml.htm<br /><br />It was on reading this that I decided that XML was not the way to proceed if all you had was a microcontroller with limited RAM.<br /><br />Just parsing the XML stream to extract the data would tax my programming capabilities.Ken Boakhttps://www.blogger.com/profile/01168707285621954181noreply@blogger.comtag:blogger.com,1999:blog-16736699.post-83614338204031631642011-04-06T07:48:35.939+01:002011-04-06T07:48:35.939+01:00Mark,
The short messaging protocol arose from a s...Mark,<br /><br />The short messaging protocol arose from a simple serial command interpreter used to send short commands to an instrument I was developing. Commands typed over a serial link were used to control different functions of the instrument. It was essentially a human readable set of commands - restricted, by way of convenience to only having to type in the shortest text strings to control the instrument.<br /><br />Some point afterwards, I realised that my simple typed commands were a good match, to what could be passed through a Pachube Feed - i.e. short sequences of comma separated arguments. It became clear that Pachube could be used to convey these commands between two simple network connected nodes.<br /><br />My background was in energy monitoring, remote sensing and home automation, where the quantity of data to be sent is not great. Small packets of data are sent at regular intervals - say every 10 seconds. The Pachube CSV Feed is a good means of transferring this data from the publishing device to the subscriber.<br /><br />The 8 bit microcontrollers used in these low cost energy monitors and sensing devices are often very lacking in resources, with only a couple of K of RAM. Many of the original devices had little support for connectivity - at best a serial port. Outputing short strings of serial data is better than nothing.<br /><br />One notable exception is the CurrentCost energy monitor which outputs a sream of XML data every 6 seconds. For the amount of information sent, the actual efficiency of real data content is very low.<br /><br />All that is needed to handle these CSV strings is a simple command interpreter and a switch statement which decodes the various commands. <br /><br />I agree that there are better ways to send longer packets of data, but given the history of this device, the resource limitations at eache end, and the nature of the Pachube Feed. <br /><br />If all you want to do is send a few sensor or meter readings, or turn a few relays on and off, the nano-tweet meets those requirements.Ken Boakhttps://www.blogger.com/profile/01168707285621954181noreply@blogger.comtag:blogger.com,1999:blog-16736699.post-42680960211483569742011-04-05T23:41:10.860+01:002011-04-05T23:41:10.860+01:00If you make one character an escape then you can a...If you make one character an escape then you can always extend the number of available codes<br /><br />e.g. abcdefghijklmnopqrstuvwxy<br /><br />then<br /><br />za,zb,zc etc<br /><br />then <br /><br />zza,zzb,zzc etc.Andy from Workshopshedhttp://www.workshophed.comnoreply@blogger.comtag:blogger.com,1999:blog-16736699.post-3793130762513006572011-04-05T23:40:54.142+01:002011-04-05T23:40:54.142+01:00Ken,
I don't understand your passion for shor...Ken,<br /><br />I don't understand your passion for short messages resulting in an over complicated messaging system. Does it really matter whether a nano-tweet is 5, 10, 50 or a 100 bytes long?<br /><br />Even serially connected they'll still take a relatively short time to communicate unless you are planning a massive system with very frequent communication. Surely it's the latency that is likely to have a much bigger impact on the system performance and having a complicated messaging system to decode on a relatively slow controller will impact the latency.Marknoreply@blogger.com