I tried to use the GPIOs on the AR7554 (AR7 EvalBoard) as described in the document:
Accessing GPIO from Linux / AirPrime AR755x,AR865x,WP710x.
First I assigned / allocated the GPIOs on the Modem (AT Interface). As you see the pins 6, 7 and 10 are assigned to function 16 = Legato / Linux:
AT+WIOCFG? +WIOCFG: 1,0,0,0,1,0,0 +WIOCFG: 2,0,0,0,1,0,0 +WIOCFG: 3,0,0,0,1,0,0 +WIOCFG: 4,0,0,0,1,0,0 +WIOCFG: 5,3,0,0,1,768,0 +WIOCFG: 6,16,0,0,1,0,0 +WIOCFG: 7,16,0,0,1,0,0 +WIOCFG: 8,0,0,0,1,0,0 +WIOCFG: 9,0,0,0,1,0,0 +WIOCFG: 10,16,0,0,1,0,0
Now I try to export the corresponding GPIO on Linux console to the filesystem side with the command:
echo “6” > /sys/class/gpio/export
Independent which GPIO is used, I always get the negative response:
[ 270.999481] The gpio6 is not supported-sh: echo: write error: Operation not permitted
How to declare the GPIO pin to be used from Linux side?