i2c raspberrypi2 support (SenseHat)?

Scott Zemerick scott at zemericks.com
Sat Dec 24 20:51:14 UTC 2016

Alan - thanks!.  This is exactly the info I was looking for!  I will review
and try it out.  I was going to start looking at the LPS25H humidity sensor

On Sat, Dec 24, 2016 at 12:40 PM, Alan Cudmore <alan.cudmore at gmail.com>

> Here is the i2c.c patch to make the sense hat display more reliable.
> Without this delay, it will randomly hang when writing out a frame of data
> to the display.
> I’m sure this is not the right solution, just a temporary fix for my
> driver. I have been doing all of this with the original Pi, so it may not
> work the same with a Pi2.
> Alan
> On Dec 24, 2016, at 10:24 AM, Alan Cudmore <alan.cudmore at gmail.com> wrote:
> 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
> Sense hat display driver in action here:
> https://www.youtube.com/watch?v=cHYxj6aW4jI
> The code to drive that demo is here:
> https://github.com/alanc98/rki/blob/rpi-drivers/sensehatdisplay_cmd.c
> 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.
> Alan
> 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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