Problem accessing GPIO pin 23 (SPI) on an Explorer board

[PieterGit]

Hi @andy-shev

I am trying to get a TI CCxxxx chip working on an Intel Edison Explorerboard (see https://github.com/EnhancedRadioDevices/915MHzEdisonExplorer ) with your eds branch 4.10rc4.

I now have the /dev/spidev5.1 file and I also have a /sys/class/gpio/export file

# ls -al /sys/class/gpio/export
--w------- 1 root root 4096 Jan  1  2000 /sys/class/gpio/export

Unfortunately accessing the GPIO pin 23 fails, e.g.:

# reset_spi_serial.py
Traceback (most recent call last):
  File "/usr/local/bin/reset_spi_serial.py", line 6, in <module>
    exec(compile(open(__file__).read(), __file__, 'exec'))
  File "/root/src/915MHzEdisonExplorer_SW/spi_serial/scripts/reset_spi_serial.py", line 3, in <module>
    s = spi_serial.SpiSerial()
  File "/root/src/915MHzEdisonExplorer_SW/spi_serial/spi_serial/spi_serial.py", line 7, in __init__
    self.cs0 = m.Gpio(23)
  File "/usr/local/lib/python2.7/dist-packages/mraa.py", line 995, in __init__
    this = _mraa.new_Gpio(pin, owner, raw)
ValueError: Invalid GPIO pin specified

This works fine on a Yocto image. Can you explain why I can't access the spi serial pin?

My libmraa version v1.5.1-18-ge386300

This is also discussed on the Intend-to-Bolus gitter, see: https://gitter.im/nightscout/intend-to-bolus?at=588532efd43728124e8ef673 . @ecc1 and @oskarpearson helped me add some of the necessary kernel parameters. I enabled CONFIG_I2C_GPIO, CONFIG_SPI_GPIO, CONFIG_GPIO_SYSFS on your x86_64_defconfig

Thanks in advance,

Pieter

[andy-shev]

Indeed, my kernel configuration doesn't have GPIO_SYSFS enabled.

Regarding to a log on the link I might give a hint: GPIO export works exactly how it's designed in upstream kernel. If libmraa doesn't support a standard way of doing things it should be fixed.

For me it looks like a completely problem of libmraa. I never used that library and never will.

By the way, I used an example to set SPI5 output on from Emutex page and it works for me (on Edison/Arduino). So, it might be also some issues regarding to absence of PCA9555L GPIO expanders, though they are sitting on GPIO 200+ lines.

[andy-shev]

Okay, I got what's wrong. Thanks for report.
UPDATE. The problematic set of GPIOs is Family 7 (I2C, 14 pins). They are located in secure block in FLIS and this requires special write access to them. Upstream solution would be ready in v4.12-rc1. It's not a big deal, but it requires to do some infrastructure changes. I will look what I can do sooner.

[PieterGit]

@andy-shev : That would be great!
I didn't know linux kernel planning for 4.12-rc1 already exists.
Thanks for your looking into the problem. If there is anything I can test or debug, please let me know.
A lot of diabetes users of openaps will be very happy with such as a solution, because it can let openaps control their insulin pump. Thanks in advance.

[VladimirAkopyan]

U guys use it for insulin pumps? Holy cow, and I thoughts controlling a greenhouse is risky cause I might ruin some salad...

[andy-shev]

Hold on, I just checked schematics and there is no such GPIO available to the user. Even for the rest 4 pins (I2C1 and I2C6) there is no possibility to switch their mode to something else (in original Edison BSP).

So, back to square 1, i.e. these are clearly 2 bugs: a) official Edison BSP is buggy, b) libmraa is crap.

P.S. But thanks for report anyway, I found one (minor) bug in the code because of this report.