Acceptable packet loss specs nRF528XX

RE: Acceptable packet loss specs nRF528XX

Kenneth — Thu, 17 Nov 2022 13:11:44 GMT

Hi again,

[quote user="Vagner Landskron"]Is there any measurements/statistics performed by Nordic?[/quote]

As part of production test and qualification there are extensive tests performed on the radio, to ensure that all nR devices delivered perform according to the production specifications. If you want to perform tests yourself to for instance measure packet error rate or similar, you can do this using for instance DTM test:
https://infocenter.nordicsemi.com/topic/struct_appnotes/struct/appnotes_nan34.html

This test is following the BLE specification for testing the radio, but the same will verify any radio protocol and can for instance output the packet error rate.

[quote user="Vagner Landskron"]Another information is that certain "channels" are cleaner than others. At the moment, in our lab, channels 21-22 are super clean and gives me really good results:[/quote]

I am not sure how your protocol is working, but it looks like you have one transmitter, and possible several devices that receive this and respond back. I assume you have ensure sufficient timing between the various devices such that they are not "talking" at the same time. If specific channels are performing better, it can be that there is less noise on the channels in specific, or that you are using an antenna that is very narrow banded, and thereby perform better on certain channels in the middle of the band for instance.

[quote user="Vagner Landskron"]Another question, if the packet fails the CRC (such as if I disable the CRC) - will I get a corrupted packet?
The way it's written here sounds like it's only for "identification" purposes.[/quote]

I don't remember exactly the details here what happens if CRC fails, I would assume it should be possible to still check the packet in RAM (even if CRC failed):
https://infocenter.nordicsemi.com/topic/ps_nrf52833/radio.html#register.PACKETPTR

Best regards,
Kenneth

RE: Acceptable packet loss specs nRF528XX

Vagner Landskron — Thu, 17 Nov 2022 06:47:01 GMT

Thanks for your support Kenneth, as always, very useful.

Is there any measurements/statistics performed by Nordic?

Another information is that certain "channels" are cleaner than others. At the moment, in our lab, channels 21-22 are super clean and gives me really good results:

Another question, if the packet fails the CRC (such as if I disable the CRC) - will I get a corrupted packet?
The way it's written here sounds like it's only for "identification" purposes.

We are considering disabling the CRC and adding some data correction algorithm instead.

RE: Acceptable packet loss specs nRF528XX

Kenneth — Wed, 16 Nov 2022 12:21:04 GMT

Hi,

The packet error rate typically increase rapidly around the sensitivity limit, but as long as the received signal strength is higher you should not expect much packet loss (close to 0%). That said though, there can be several reasons for packet loss due to interference or poor link budget:

- the design is not properly tuned for optimal performance, both output power and antenna may need tuning to ensure good link budget, adding output power only one one side of the link may not improve the link budget if the other side of the link is still using less output power. Make sure to follow the pcb guidelines and get someone to review and tune the design.

- serial activity can have an impact on the received signal, we have for the different variants of the nRF52 series identified some pins that can in specific affect the perfomance, for instance for the nRF52833 you can find the recommended usage column for each variant listed here:
https://infocenter.nordicsemi.com/topic/ps_nrf52833/pin.html

- interference can cause packet loss, this can be either interference from wifi, bt or other 2.4GHz operation, but it can also be conducted interference through USB, in specific USB3 is very noise in the 2.4GHz band, ref:
https://www.usb.org/sites/default/files/327216.pdf

Best regars,
Kenneth