BananaPI M1: gpio.add_event_detect not working after switch to vanilla kernel

[hcooh]

Hi,

 

I was on the legacy kernel until recently with my bananaPi M1.

I switched to the vanilla kernel but since then, when I try to use the GPIO python library (for bananapi from LeMaker github), it works quite well except for functions

gpio.add_event_detect() or GPIO.wait_for_edge(channel, GPIO.RISING)

This usually disconnect my network and the event is never detected.

I have to reboot the PI to restore the state. 

 

Also, a normal read/write state GPIO.input(PIN_NUM) works perfectly...

 

I assume it is due to the vanilla kernel but could not find any documentation on why this is happening...

 

Any answer/comments would be much appreciated!

Let me know if you need more info on my setup.

Thanks and regards,

Fabien

[Igor]

This might help you:

http://linux-sunxi.org/GPIO

[hcooh]

Hi, thanks for the link,

 

After some investigations and debugging, I got everything working again.

So I thought I would post my findings here if that can help someone else.

 

Basically, the RPi.GPIO python library is accessing the GPIO via two different methods for different actions:

-          Direct access and write to registers for setting pull-up and pull down, input and output

-          Using the /sys/class/gpio for all edge event detection

 

Switching between legacy and mainline kernel change the /sys/class/gpio numbering template:

-          Legacy: the gpio-sunxi kernel module is managing the creation of /sys/class/gpio/gpioXX (where XX is the board pin number)

-          Mainline: the kernel (no more specific module) is managing the creation of /sys/class/gpio/gpioXXX (where XXX is the physical port number see http://linux-sunxi.org/GPIO)

 

So to have the LeMaker RPi.GPIO library working again, some modifications are needed to the /source/event_gpio.c.

I have made the changes on my github repository:

https://github.com/hcoohb/RPi.GPIO_BP/tree/bananapi

(valid for bananapi branch only, I haven’t pushed the changes for bananapro branch)

 

Hope that helps anyone.