Friday, 29 July 2016

Console application for MTAPI

No, this is still not the power measurement post.  Richard will get around to it soon, honest.

We spend a lot of time playing around with TI's CC2538 Zigbee chip running Z-Stack, which means that we spend a lot of time programming other embedded chips to talk TI's Monitor and Test API serial protocol to it.  Needless to say, debugging at more than one CPU's remove can be a tedious exercise, and there's nothing (that I know about, at least) that will allow you to talk MTAPI to a CC2538 from your nice, comfortable Linux development environment.

Enter MTConsole, in the repository.  In a fit of enthusiasm, and a strong desire to be able to script tests, I've put together a Python program to translate to and from MTAPI.  It is limited at the moment, and some areas are, to be blunt, not very pretty.  It falls over with an exception on a parse error, for example, because that was what I wanted when testing the parser.  That will get visited with fire and the sword when it first annoys me in real use.

So far I've put a lot of effort into parsing binary input (from the CC2538) into text, and not much into parsing text into MTAPI commands.  That will be changing as I need more commands (fire and the sword, people), but at the moment it's not useful for much more than proving that your chip is up and talking to the outside world.  Useful as that is, I would eventually like to get to the point where I can script it well enough to mock up complex command sequences.

Please feel free to grab and use as the mood takes you.  Patches, bug reports, comments and suggestions are always welcome, just bring your own sword.

Wednesday, 20 July 2016

Hacking Wireshark for fun and profit

We've been working on some low-power Zigbee sensors recently, based on CC2538 / ZStack 1.2.2 and running Zigbee HA 1.2.1 ; whilst we were doing this it occurred to us that Wireshark could usefully decode a few more of the IAS Zigbee messages into something useful.

So we did that.

It also turns out that some of our clients (and compliance test houses) use the very nice Ubiqua protocol analyser tool

However, we are a Wireshark shop.

Step up Vadim , who contributed a bunch of patches in Wireshark bug 7426. Those had rotted a bit, so I resurrected them and the upshot is that the repository now contains a bunch of things that Zigbee hackers might find fun:

  • Better decoding for Zigbee IAS messages - from Rhodri James.
  • Support for CUBX, TI SmartRF Studio and Ember Insight Desktop file formats as per Vadim's patch.
  • Support for more recent Ubiqua 3 file formats (at least, on the traces I have here).
  • A nasty backdoor mechanism so that you can decode Ubiqua traces which don't contain the TC key transport packet in the trace (Ubiqua stashes this in a separate table, and we pass it round the back to the Zigbee packet dissector).

One day I will get around to trying to push this lot upstream, but I suspect we will want a better way to do the backdoor key transport than the ugly hack I have in there at the moment.

Anyway, if you feel minded, grab it, enjoy and do report any bugs you come across (and I will do another post on power measurement for low-power radio, honest).