When can the PACKETPTR register be updated?

[abkirchhoff]

I am using the radio in the nRF52832 to support a custom protocol. I would like to send two packets in a row, each with different payloads, on the same frequency. When can I safely update the PACKETPTR register to point to the new packet contents? After the PAYLOAD event or after the END event?

After the PAYLOAD event would be ideal, as this would allow me to use the END->START shortcut, provided I can update the PACKETPTR register in the time it takes to transmit the CRC. The datasheet actually says to wait until after the DISABLED event, but I am hoping that is not the case.

Thanks!

[Susheel Nuguru]

Hi,

@abkirchhoff : It should be ok to use END for RX as well as TX, as long as we have a CRC > 0 byte. If the CRC is 0 byte I do not think we can guarantee that the last byte received at END is moved to RAM before the END event has reached to the CPU. I assume that the PS has written DISABLED to make it simple and safe keeping BLE in mind and forgot that RADIO does not need to be disabled for every transaction.

@Martijn: The PACKETPTR is latched (double buffered) on START task, i.e. the EasyDMA stores a copy of the register on START. So you were right, we can update it any number of times before TASK_START and value at the time of START task will be latched to be used by EasyDMA.

[abkirchhoff]

Thanks Aryan for looking into this question.This information is very useful. Thanks Martijn for you participation as well.

I didn't mention it before, but I am sending packets to a nRF24L01+, which limits me to 32 byte payloads. I am hoping to send two consecutive packets to the nRF24L01+ as it has a 3 packet FIFO, and with this new information, it looks like the nRF52832 will be able to do so.

[Martijn]

great! thank you for confirming!