Testing the I2C Portexpander (GPIOs EdgeKit)
EdgeKit has maximum two internal I2C port expanders for different use cases, so it is possible to have more than just the standard GPIOs available.
One I2C GPIO expander is located on the mainboard and is therefore always implemented in EdgeKit. A second GPIO expander is located on the industrial board and is needed for the following interfaces:
- Opto Isolated GPIOs
- RS communication features
- relays
Which GPIO Expander is available can be seen with the following command:
cat /sys/kernel/debug/gpio
You see different gpiochips, with different parent namings:
- Mainboard GPIO expander -> parent: i2c/0-0020
- Industrial GPIO expander -> parent: i2c/0-0021
Information: Input trigger timing + Output trigger timing = max. 7.2ms
Testsetup: A frequency generator send logical highs and lows to an GPIO behind the I2C GPIO expander. This input will be registered by a bash-level code and send the same value to an output GPIO, which is also behind the same I2C GPIO expander. The test was performed with an EdgeKit (Xavier NX).
