gpio.rst

GPIO via Greybus

After running gbridge, if the board in use exposes GPIO via Greybus, then the Linux kernel will create /dev/gpiochipN entries for you.

Just to make sure that we're interacting with the Greybus GPIO device, run the following (toggling random GPIO can sometimes have negative consequences).

sudo gpiodetect | grep greybus_gpio
gpiochip0 [greybus_gpio] (32 lines)

Most GPIO controllers expose a nubmer of GPIO, so it's important to know which physical pin number should be toggled and what wiill happen when we do so.

In this case, we will toggle a number of pins on the cc1352r_sensortag that are each connected to separate red, green, and blue LEDs.

#!/bin/bash
# Blinky Demo for CC1352R SensorTag

# /dev/gpiochipN that Greybus created
CHIP="$(gpiodetect | grep greybus_gpio | head -n 1 | awk '{print $1}')"

# red, green, blue LED pin numbers
RED=6
GREEN=7
BLUE=21

# Bash array for pins and values
PINS=($RED $GREEN $BLUE)
NPINS=${#PINS[@]}

for ((count=0; count < $COUNT; count++)); do
  for i in ${!PINS[@]}; do
    # turn off previous pin
    if [ $i -eq 0 ]; then
      PREV=$((NPINS-1))
    else
      PREV=$((i-1))
    fi
    gpioset $CHIP ${PINS[$PREV]}=0

    # turn on current pin
    gpioset $CHIP ${PINS[$i]}=1
  done
done

The :file:`blinky.sh` results can be seen on YouTube.