CRC on the nrf52840

[kongstrupp]

Hello!

Regarding the CRC on the nrf52840 the specifications make it clear that the maximum length of the CRC is 3 bytes, We are working on an industrial communication protocol that we want to implement on the nrf52840. This protocol needs 4 bytes crc (crc32), is there a workaround for this? 

Thanks! 

[kongstrupp]

Okay I think there is some confusion but I will try to clarify a bit.

So, IO-Link Wireless, uses a 4 byte CRC for each packet, it sends packets back and forth between slave and master and they both use a 4 byte CRC on each packet, when looking at the radio peripherals in the specification each received packet and transmitted packet uses the hardware module CRC which only support 3 bytes, consider this package down below, this is what is called a "configuration downlink" in the IO-Link Wireless specification, it is a communication exchange from a master to a slave, it is used for configuration purposes.

Now the big question, can you configure the radio it in such a way that it can still support 4 bytes CRC via software? So hypothetically you implement an IO-Link Wireless stack on the nrf52840 board and use a 4 byte CRC but it works via software and NOT via the hardware module, or maybe, the software CRC can complement the hardware CRC? so that is becomes 4 byte CRC.  Do you think that that is possible? and if so, how can you do that?

Best regards

[Edvin]

Hello,

I see. So just to clarify, you can not use the Bluetooth stack (Softdevice) for this. But if you were to implement your own radio protocol, you can implement a 4 byte CRC and attach it to the end of your payload. If you do this, please remember to disable the radio's built in CRC, by setting the NRF_RADIO->CRCCNF register to 0x00000000, which will exclude the HW CRC from the packet. 

kongstrupp said:

or maybe, the software CRC can complement the hardware CRC?

That is more complicated. I wouldn't recommend that.

Best regards,

Edvin

[kongstrupp]

Hello Edvin, Can we have a live meeting with you on Zoom? That would mean a great deal for us if you could, This is pretty hard to discuss in a forum like this

Thanks a lot

Best regards!

[Edvin]

Actually, I don't think it is as effective as you may assume. I too need to look up things to be able to answer questions. Was there something in particular you wanted to ask?

BR,

Edvin

[kongstrupp]

Well we really need to know how this shortcut of 4 bytes CRC would do in terms of timing and how effective it would be, since you said that it would be possible to add this extra CRC on received packets in the radio on the nrf52840.