• From: Mountain View California
  • Registered: 2009-08-14
  • Posts: 7

Topic: Daughter boards and SPI programming

For a number of projects I am interested in developing alternate daughter cards for the chumby to replace the one normally on the end of the chumbical. Thank you to the chumby engineers for making it so easy to get at least basic functionality with a replacement daughter card working. I have a couple of questions about taking things to the next level.

SPI drivers:
I would like to add my own sensors and coprocessors which communicate with the chumby over the chumbical SPI as the gyro and personality coprocessor do now. I found the accel driver on the device at /drivers/chumby_accel.ko but can't seem to find the source code. Are these drivers deliberately closed source? There are already numerous posts asking for a way to add SPI communication. It seems like just the source for chumby_accel.ko would go a very long well to helping me and others.

Licensing:
Would Chumby Industries have a problem if I made alternate daughter boards available to other chumby hackers though something like Circuit Monkey?

The Chumby One:
Will the new chumby also have a chumbical with daughter board? If so will the chumbical pinout be the same or similar? For that matter, will the existing squishy chumby continue to be available?


Any response from Chumby engineers, even a final "no you will never get the SPI driver code," on these topics would be greatly appreciated.

DanielC's Website

  • Registered: 2008-06-27
  • Posts: 518

Re: Daughter boards and SPI programming

You'll probably want to get the datasheet for the i.mx21, which can be found on the wiki page at http://wiki.chumby.com/mediawiki/index. … for_chumby

You'll then want to get the Linux source, which is on the wiki page at http://wiki.chumby.com/mediawiki/index. … for_chumby

The source for the SPI accelerometer driver is in drivers/char/chumby_accel.c

Not too sure about the rest of the questions.

  • From: Mountain View California
  • Registered: 2009-08-14
  • Posts: 7

Re: Daughter boards and SPI programming

Thanks for the pointer. The accel driver source is a big help to getting started. Do you also know where the code which communicates with the personallity eeprom is?

Someone should edit the wiki to have a page on the chumbical, SPI, and links to the driver source. The old sensor package source code on the website doesn't seem to be applicable anymore and this isn't the first time it's come up.

DanielC's Website

  • Registered: 2008-06-27
  • Posts: 518

Re: Daughter boards and SPI programming

I believe the personality eeprom also lives in that same module/file, as they both live on the same bus.  It's actually two separate drivers in one source file.

  • Duane
  • Duane
  • Blue Octy
  • Offline
  • From: San Diego, CA
  • Registered: 2006-08-24
  • Posts: 8,197

Re: Daughter boards and SPI programming

On the issue of licensing - there are no restrictions on the creation and distribution of daughterboards.  We created and documented the chumbilical expressly for this purpose.

If you distribute them with software that's derivative of ours, then of course you'll need to abide by the requirements of the software licenses (making source available under the GPL, etc).

The "squishy" chumby will continue to be made available.  Many people prefer that design and it's somewhat iconic for the company.

We'll be posting the schematic of the Chumby One shortly so you can compare with the classic chumby.

Duane's Website