I2C Read Register during GPIOTE callback

RE: I2C Read Register during GPIOTE callback

Nick_RA — Wed, 01 Oct 2025 13:53:36 GMT

OK, will give the work queue a go, it should be OK as I have until the end of the packet to play with time-wise after all - I guess the word "queue" put me off as it implies deferred operation.

RE: I2C Read Register during GPIOTE callback

Kazi Afroza Sultana — Wed, 01 Oct 2025 11:41:03 GMT

Hello,

As Fischer said, you can not perform a I2C reads from an ISR on nRF54L15 with zephyr. The method works offloading workthread needs to consider some latency.

You can read this previous case Source: I2C Read/Write functions in GPIO Interrupt. It's for nRF52840 but still same principal.

Thanks.

Kazi

RE: I2C Read Register during GPIOTE callback

Turbo J — Mon, 29 Sep 2025 17:46:48 GMT

Hand over to an empty work queue is in the order of a few micro seconds (you only wait for the IRQ handler to finish). Your I²C bus will likely cause a lot more delay.

RE: I2C Read Register during GPIOTE callback

Nick_RA — Mon, 29 Sep 2025 16:26:16 GMT

Surely passing to a kernel work queue is exactly what I don't want in terms of latency? I need to obtain the value in the radio's RSSI register in real-time while it is receiving the packet... i.e. in a few milliseconds of decoding the magic number bytes.

Note there will be other stuff going on including BLE advertising, GATT connection and possibly printk() via UART although not all at once.

RE: I2C Read Register during GPIOTE callback

Turbo J — Mon, 29 Sep 2025 11:18:28 GMT

You are not allowed to call "blocking" functions in an interrupt handler and most device/bus driver calls are blocking.

Try a dedicated work queue.