Adding addtitional Sensors to Openmoko

Andy Green andy at
Mon Oct 6 17:00:02 CEST 2008

Hash: SHA1

Rob Williams wrote:
> Andy Green wrote:
>> Hash: SHA1
>> Michael Tansella wrote:
>>> Hi,
>>> we want to create an additional Board which includes some sensors bundled with 
>>> a Microcontroller. What do you think is the easiest way to connect it with 
>>> the Openmoko. Can we use an UART Port, if yes, what's the best way to get 
>>> access to it?
>>> AFAIK we have 3 UART Ports available. One is used for GSM Modem one for GPS 
>>> and one for Console.
>>> I don't understand what's the third one (Console) for. Can we use it for our 
>>> project? 
>>> Do you recommend another possibility? SPI?Are there any free ports which are 
>>> supposed to be used for hardware extensions?
>> Debug console sets information from bootloader and linux dumped down it
>> on boot, and you can log in there as well.  If you stop the tty process
>> spawning in inittab, after boot you'd be able to use it.
>> There is an SPI interface on the testpoints near the debug connector.
>>> We would like to avoid using USB because of its complexity.
>> USB is definitely the best solution if you can get over the hump of
>> getting started with a programmable device for it.  Everything else
>> means the phone is tethered permanently to your other board.
> USB is actually a lot easier than you can be led to believe, as there
> are a number of existing demo/breakout USB boards designed just for this
> type of application. My favourite are the Phidgets, as they offer not
> only a range of boards with digital/analog input/outputs, but they'll
> also work with you to do custom designs/projects and offer a wide range
> of other types of sensors/etc that you can utilize along with them. They
> also offer the best software support I've seen for this kind of hardware
> by supplying development tools and libraries for virtually every
> programming language under the sun. I don't have an OpenMoko device to
> play with right now but I've cross-compiled their demo apps (along with
> my own basic C apps based on their libraries) to various ARM platforms,
> so shouldn't be a problem from that end either.

Yes, I used some devices that used to be from Cygnal, now Silicon Labs a
couple of times.  There are canned "libraries" of sources available to
make them appear as serial device class and so on.

The advantages are pretty strong, not only can you remove them or swap
them around, but power is taken care of too.  You can also plug them in
a desktop or laptop randomly.

sdcc project also provides gpl compile tools for 8051 derivatives like that.

- -Andy
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