GPIO
GPIOs (General Purpose Input Outputs) are user-controllable pins that can be used to interact with external circuits.
Hardware
The table illustrated below shows the number of GPIOs available on the Omega2/2+ vs Omega2S/Omega2S+.
| Omega2/2+ | Omega2S/2S+ | |
|---|---|---|
| GPIOs | 18 | 37 |
Electrical Ratings
GPIO Operating Voltage:
| Parameter | Minimum (Vdc) | Minimum (Vdc) |
|---|---|---|
| Input HIGH | 2.0 | 3.6 |
| Input Low | -0.3 | 0.8 |
| Output HIGH | 2.4 | 3.3 |
| Output LOW | - | 0.4 |
The Omega2/2+ GPIOs are not 5V input tolerant!
Connecting a signal to an input pin below the minimum LOW or above the maximum HIGH voltages may damage your Omega device!
Standard 5V logic devices typically accept 3.3V as a logical HIGH, however, the output logical HIGH is in the range of 4.4V to 5V. This means the Omega can output to a 5V logical device, but input from the 5V logic device would damage the GPIO input circuitry.
Multiplexed Pins
A number of the available pins can be used for multiple purposes other than general-purpose input/output when needed. Such pins are referred to as multiplexed pins.
See detailed explanation of Multiplexed Pins.
Software
The GPIOs can be accessed through the GPIO sysfs interface, see the documentation for details.
The GPIO sysfs interface is deprecated but is currently the best option for userspace GPIO access. More context is available in this post by Luz on the Onion Community.
GPIO Numbering Issue in OpenWRT 22.03
This only applies to Onion's OpenWRT 22.03 firmware releases
In earlier 22.03 releases of the Onion Omega2 firmmware, the GPIO numbering in Linux did not match the device's actual GPIO numbers. This was due to changes in the kernel around GPIO handling.
- GPIO 0 - 31 ⇒ GPIO 480 - 511 (GPIO n + 480)
- GPIO 32 - 63 ⇒ GPIO 448 - 479 (GPIO n + 416)
This has been resolved in Onion's OpenWRT 23.05 firmware releases and all releases going forward
Interacting with GPIOs
Command Line: Use the GPIO sysfs interface for basic testing and interaction with GPIOs. For detailed usage instructions, refer to the GPIO Sysfs usage documentation documentation.