TS-4900 DIO

The i.MX6 GPIO are available using the kernel's sysfs. See the kernel's documentation here for more detail. This interface provides a set of files and directories for interacting with GPIO which can be used from any language that can write files. For example to toggle CN1_89/EIM_A22 the kernel maps this to GPIO 48. See the table below for the full IO listing.

To interact with this pin, first export it to userspace:

echo "48" > /sys/class/gpio/export

If you receive a permission denied on a pin that means it is claimed by another kernel driver. If it succeeds you will have a /sys/class/gpio/gpio48/ directory. The relevant files in this directory are:

 direction - "out" or "in"
 value - write "1" or "0", or read "1" or "0" if direction is in
 edge - write with "rising", "falling", or "none"

# Set GPIO 48 high
echo "out" > /sys/class/gpio/gpio48/direction
echo "1" > /sys/class/gpio/gpio48/value
# Set GPIO 48 low
echo "0" > /sys/class/gpio/gpio48/value

# Read the value of GPIO 48
echo "in" > /sys/class/gpio/gpio48/direction
cat /sys/class/gpio/gpio48/value

As an output, the in can be written to 0 for low (GND), or 1 for high (3.3V). As an input the GPIO will have a 100k pullup. The GPIO pins directly off of the i.MX6 processor support an absolute maximum of -0.5 to 3.6V. It is also possible to use any processor GPIO as an interrupt by writing the edge value, and then using select() or poll() on the value file for changes.

Note:

For custom carrier board designs, the 100k pullup is added in the device tree when the pin is specified as a GPIO.