i2c raspberrypi2 support (SenseHat)?

Alan Cudmore alan.cudmore at gmail.com
Sat Dec 24 15:24:07 UTC 2016

Hi Scott,
The raspberry pi BSP uses the newer Linux I2C API, which is used in a few BSPs. 
I have been able to use the I2C API for a few devices on the Pi, and I have been slowly working on trying to support the sense hat. 
I have a sense hat display driver in the “dpi-drivers” branch of my RKI project:
https://github.com/alanc98/rki/tree/rpi-drivers <https://github.com/alanc98/rki/tree/rpi-drivers>

Sense hat display driver in action here:
https://www.youtube.com/watch?v=cHYxj6aW4jI <https://www.youtube.com/watch?v=cHYxj6aW4jI>

The code to drive that demo is here:

The project is setup so you can add and test drivers without adding them to the RTEMS tree. 

The sense hat display driver does bring out a bug ( maybe a race condition ? ) in the I2C Pi BSP code. I had to add a delay in the Pi I2C support code to make the sense hat display work correctly. I can’t seem to locate that patch right now, I’ll have to find it. 

I was starting to work on the HTS221 Temp/Humidity driver next.  
It would be great to get someone else helping with the rest of the drivers. 

I was also trying to test the SPI support, but I have been unable to get a driver for my simple SPI device to work. ( works on Arduino and Pi/Linux ). I think we need to convert the SPI support in the Pi BSP to the new SPI framework anyway, so it’s worth revisiting the SPI implementation. 


> On Dec 23, 2016, at 11:14 PM, Scott Zemerick <scott at zemericks.com> wrote:
> Is anyone currently using i2c with the raspberrypi2 - and more specifically the SenseHat?  The i2c bsp code looks mostly complete, but I am confused as to which i2c API functions to call, with some concern that the i2c bsp support isn't complete.  A quick comparison of the pi i2c code with the spi code shows some design differences, with the latter looking more complete.  I plan on digging more into the pi bsp, but I would like to know the current state and if anyone has a basic example of pi i2c.  Thanks! 
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