I am able to access the GPIO’s in C using the fopen and fgets commands to read (and cycle through) all the required GPIO lines, and check their status.  This is just basically just doing the same job as “cat /proc/gpio/GPIO##” would be.  I now need to be able to change their state to “GPIO out set” or whatever from within C.  The wiki says to use fread and fwrite (on /proc/gpio/GPIO devices) but I have had no luck with either.  I am dubious of using the memory mapped registers as I am not very good at coding.  Can anyone offer me any help on using the /proc/ interface from within C? Is the /proc interface also sensitive enough to detect logic edge changes on one of the GPIO lines with a high degree of accuracy as this is how I hope to eventually sense the Pulse Width Modulation signals too?