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Simple port IO on MPC5121e and Linux - an impossible task ? :)

Question asked by cédricfoissac on Mar 21, 2013
Latest reply on Mar 26, 2013 by cédricfoissac



I can't believe it is so complex to set a simple chipselect on a MPC5121e running linux.


Gpio is detected (kernel is compiled with support of it, and i got gpiochip_find_base: found new base @224 in dmesg (kernel 3.0.4 with xenomai)


But i'm unable to access it through /sys/class/gpio. I can successfully export a pin (ie, if i type cat 224 > export, gpio224 is created), but i can't successfully control it:


echo "out" > /sys/class/gpio/gpio224/direction

cat /sys/class/gpio/gpio224/value


echo 1 > /sys/class/gpio/gpio224/value

cat /sys/class/gpio/gpio224/value



My need is a simple chipselect (well, 3 chips - select ), for a custom design. Running linux is mandatory. I suspect the MPC5121 to be in the bad function mode, so:

- does anyone knows how to change mode ? What register can i acces and how ? does it worths a try ?

- does anyone successfully perform simple IO control ?


Last thing, i have tryed to access internal registers through /dev/mem, but no success. There are very few ressources available for this microcontroler, but i'm stick to it. Perhaps anybody knows how to access (read) internal registers with /proc or sys-fs ?


Thank you for your help !