AVR32 GPIO CS-423 Dick Steflik

What is a GPIO GPIO – General Purpose Input/Output  Flexible software control digital signal  Each GPIO represents a bit connected to a MCU pin or ball (on the BGA)‏ AVR32 GPIO Processor features  An input change interrupt - Enables level detection on any I/O line  Glitch filtering – reject pulses of < ½ clock cycle  Control of the internal pull-ups on I/O lines  Inout visability and output control

Use of GPIOs Configuration should be done in the board setup code, once setup can be used from:  User-space Slow Mainly used for turning something on/off Can be used from scripts or C  Kernel-space Device drivers Fast

/dev GPIO Interface Uses the configfs ram based virtual file system  Mounts at /config (already done on NGW100)‏ mount -t configfs config /config  Exists only for the current boot session Could be made to be created by running a script at system startup, script would have to create each object  Manipulated by mkdir and rmdir to create and remove objects

/config NGW100 already has three predefined GPIOs  bootled – GPIO0  leda – GPIO1 bit 19  ledb – GPIO2 bit 19 each GPIO directory has 4 files gpio_id – which GPIO (0-4)‏ pin-mask – which pin(s) oe_mask – output enable mask enabled – enable the GPIO (0-disable, 1-enable)‏

/dev GPIO0 GPIO1- bit 19 LED A GPIO2 – bit 19 LED B

Using Define devices in the shell Use them from C using C I/O functions read/write/poll define a file descriptor for the file in /dev  for output write to that file descriptor  for input read from the file descriptor  for waiting on a condition poll the filedescriptor

GPIOs in a module GPIOs can be done faster and easier by doing from a kernel module (this is similar to what we did with the 2313s)‏

LED Interface