AVR32 GPIO

1
AVR32 GPIO

• CS-423
• Dick Steflik

2
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 lt ½ clock
  cycle
• Control of the internal pull-ups on I/O lines
• Inout visability and output control

3
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

4
/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

5
/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)?

6
/dev

• GPIO0
• GPIO1- bit 19 LED A
• GPIO2 bit 19 LED B

7
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

8
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)?

9
LED Interface