40-Pin GPIO Interface | Radxa Docs

[giscus[bot]]

40-Pin GPIO Interface | Radxa Docs

The Radxa Cubie A7Z features an onboard 40-Pin GPIO (General Purpose Input/Output) interface, providing highly flexible interface support for hardware expansion.

https://docs.radxa.com/en/cubie/a7z/hardware-use/pin-gpio

[Brannan-repo]

In the GPIO Pin Number Calculation Example, it shows PB7 is the same as Pin 39("GPIOCHIP0 -> 7 + 32 * (A ~ K) -> 7 + 32 * 1 -> 39", but Pin 39 in the table(GPIO Features) shows that Pin 39 is Ground.
The gpio_output.py script also shows "PB7 (output) → maps to pin 39 of /dev/gpiochip0"
This seems incorrect. PB7 should be PIN40.
The script also says "PB8 (input) → maps to pin 40" but the table shows PB8 mapping to pin 38.
And based on the calculation provided, PB8 = Pin 40.

Can someone explain these contradictions so I do not damage my board?

Thanks!

[Brannan-repo]

And if the Calculation Example is correct, How can you calculate other Pins, like PD12?
Would the calculation be: 12 + 32 * 1(or 3?) which equals 44. But the table shows it's Pin 19

[Milir-Radxa]

The index numbers in the middle of the GPIO table are not related to the actual control pin calculation; they are mainly provided to help users locate pin positions.

If you want to control a specific pin, you should calculate it using Function1 in the table. The calculated result is the actual parameter you need to fill in your program.

Control example: PD12 -> GPIOCHIP0 -> 7 + 32 * (A ~ K) -> 7 + 32 * 3 -> 103, so the code should be:
gpio_out = GPIO(GPIOCHIP0, 103, "out")

[tangzz-radxa]

Thank you for the detailed report, and please accept our apologies for the confusion.

You are correct that there is an inconsistency in the documentation. The GPIO Features table shows:

• Pin 39 → GND
• Pin 40 → PB7

However, the Calculation Example states that PB7 maps to Pin 39, which contradicts the table.

Based on the GPIO Features table (Pin 40 = PB7), the correct calculation result for PB7 should be Pin 40, not Pin 39. The example appears to have an error in the result.

If you need to use PB7 as GPIO, you should reference Pin 40 of /dev/gpiochip0, not Pin 39. Using Pin 39 (which is GND) would short the signal to ground and could damage the board — your concern is valid.

We will fix the calculation example in the documentation. Thank you for helping improve our docs!

[Kyuuza]

anyone know how to initialize a pps device/driver on this sbc? I can see the gps device on /dev/ttyMSM0 but I cannot for the life of me init the pps device

specifically this gpio layout on this rtk hat "https://www.waveshare.com/wiki/LC29H(XX)_GPS/RTK_HAT#Hardware_Connection" (pin12)

any help would be appreciated