aioble vs RGB LED shared hardware resources

[lievenleroy]

Another aioble issue on Nano RP2040 Connect:
The board's RGB pixel is connected to the wifi/Bluetooth chip. So setting it requires talking over SPI to that chip.

I have this working using sample code from here. But once I initialize aioble, I can no longer reliably configure the pixel.

My BLE code is closely modeled on the temperature server example in the aioble Github. Roughly, my code looks like:

• init SPI interface for pixel
• init aioble
• start asyncio tasks for BLE advertising and to blink the pixel

Either task running solo works fine, but if I run both tasks the pixel fails to blink. I'm guessing aioble service interrupts are stepping on other SPI communication in progress. Is there a way to suspend aioble activity for a period of time (critical section)? Or a mutex or other means that the resource should be shared through?

[lievenleroy]

Updates:

• There's an alternate way to control the RBG LEDs via LED_BLUE/LED_GREEN/LED_RED pin definitions in the machine lib, but it has the same issue as when I control them using the code sample I mentioned above: doesn't work when aioble is in use
• Using a simple critical section (disable_irq/enable_irq) doesn't work, since it disables the ability to receive SPI responses

[jimmo]

@lievenleroy It would be interesting to know whether it's aioble or just bluetooth at all. i.e. if you just use the lower-level BLE api, e.g. https://github.com/micropython/micropython/blob/master/examples/bluetooth/ble_temperature.py

I'm not surprised that there are issues controlling the LEDs via SPI directly from Python, you should definitely use the machine.Pin abstraction here. But yes this should work.

Maybe @iabdalkader has some suggestions?

[iabdalkader]

@jimmo

Ah yes I saw the same issue a few days ago, I don't think it has anything to do with aioble. I think it's the firmware, it doesn't initialize the SPI peripheral/control pins when the module is reset in Bluetooth mode, and the SPI bus is required to control external pins. I'd suggest using the LED pin instead, which is controlled directly by the RP2040, while using Bluetooth.

EDIT: Some more info, this function initializes bluetooth: https://github.com/arduino/nina-fw/blob/master/main/sketch.ino.cpp#L117
This one initializes WiFi (and SPI) : https://github.com/arduino/nina-fw/blob/master/main/sketch.ino.cpp#L159
You can see the firmware just takes a different path on reset depending on the reset mode. Note I'm not sure but there might be some shared pins between the BT/UART and the SPI interfaces too, need to check to confirm, so it might be impossible to use the two interfaces at the same time.

I have this working using sample code from here. But once I initialize aioble, I can no longer reliably configure the pixel.

@lievenleroy You don't need all that code to control the RGB LED, rp2's machine.Pin supports externally controlled GPIO, so you can just use machine.Pin("LED").value(1) and the same goes for externally controlled ADC channels btw (machine.ADC supports them).