NRF52 Radio CCM errors

RE: NRF52 Radio CCM errors

freelon — Tue, 08 Jun 2021 18:32:42 GMT

Hmm, ok I'll try comparing our code to that. We do use the pre-programmed PPI channel 25 on rx, but not on tx.

RE: NRF52 Radio CCM errors

Sigurd — Tue, 08 Jun 2021 09:57:18 GMT

[quote user="freelon"]But essentially my issue is I get ccm failures with bigger payloads, but not smaller ones and I was wondering if this is a known issue?[/quote]

I'm not aware of any issues here.

I took a look at the Zephyr BLE LL, and here, and it uses the pre-programmed PPI channel 25, to trigger TASKS_CRYPT (triggers on RADIO->EVENTS_ADDRESS). Maybe you can try something similar in your code, assuming it fits your use-case.

RE: NRF52 Radio CCM errors

freelon — Mon, 07 Jun 2021 17:38:45 GMT

The code I was referring to is in the proprietary rf protocol I mentioned.

But essentially my issue is I get ccm failures with bigger payloads, but not smaller ones and I was wondering if this is a known issue?

RE: NRF52 Radio CCM errors

Sigurd — Mon, 07 Jun 2021 12:07:03 GMT

Hi,

[quote user=""]I noticed that in the code, the CCM is configured with the PPI module starting the encryption after the ENDKSGEN event is fired, with a note saying that using the shortcut results in failure with bigger payloads. [/quote]

I'm not sure what code and note you are referring to here.

We have a example that implements a simple encryption library based on the CCM module here, you might find that helpful:
https://github.com/NordicPlayground/nrf52-esb-ccm-example/tree/master