nRF24L01+ Received Power Detector

[JasonWu]

Dear Nordic engineer

  I have a question that How to use register 09.Please give me an example.

Thank you

Best wish

Jason

[DavidHJC]

I have the same question with you.

In datasheet , it said that the RPD can be read out at any time while nRF24L01+ is in receive mode. But if we want to read 0x09 register with SPI, we must let CE low. At this time , NRF is no longer RX mode at all ! How to do with this?

By the way ,is CD register just detect  power in the RF you had already set regardless of  P0 - P5 Address?

[ovrebekk]

Hi David

You don't need to set CE low to read configuration registers. Maybe you are thinking of the CSN line?

All configuration registers can be safely read during RX or TX mode, but if you want to write to the registers and change the RF configuration you will have to disable the radio, that is correct. 

Best regards
Torbjørn

[DavidHJC]

Oh my god! I always consider that reading register must low the CE! Thank you very much!
I want to use 0x09 register to detect whether the RFchannel I used is disturbed by WLAN or not. Am I right?

[ovrebekk]

Hi David

You can use the RPD bit to try and evaluate if there is a lot of activity on the channel, that is correct, but keep in mind that it is not a fool proof method. 

The activity on a WiFi network will change during use, and few networks are on 100% of the time, so you are not guaranteed to detect WiFi activity by using the RPD bit. 

Another way to evaluate channel quality is to look at the retransmit count and packet loss between the TX and the RX whenever you try to transmit data. If you see a high number of retransmits and/or packet loss on a specific channel it could be a sign that you have a lot of interference on that channel. 

Best regards
Torbjørn

[DavidHJC]

Thank you Torbjørn!

Yes you are right.

In the TX ,there are many ways to evaluate if there is a lot of disturbance on the channel.

But in the RX, I think that there is no way to evalute the situation but using 0X09 register.

For example, when Tx AND Rx has no conection or Tx message is a random signal, how dose the RX device evaluate interference on this RF channel???

[ovrebekk]

Hi David

I agree with you, if you don't have a link running sending packets repeatedly then you can't use the methods I described. 

In this case the RPD bit would be a better choice. 

Just keep in mind that the RPD bit doesn't discriminate between unwanted noise and a signal from a TX device that you might want to listen to. 

Best regards
Torbjørn

[DavidHJC]

En , I will combine CD & IQR or status register together.

My device works normally most of the time but some time (about last 10 mins) has high number of retransmits. I think it is disturbed by WLAN in the office. Am I right?

Do you have any application reference about  avoiding noise from WIFI and Buletooth?

I am hopeless! help! help!

[ovrebekk]

Hi David

What is the distance between the TX and the RX? 

Do they have line of sight, or are there walls or other things in between?

Do you run communication in a single, static channel, or do you use some kind of frequency jumping scheme?

The most common way to handle interference is to switch to a different RF frequency when the number of retransmits increases. By using several different channels across the 2.4GHz ISM band you can typically find a free channel that is not affected by WiFi unless you have many different WiFi networks in close proximity. 

We made the Gazell protocol for this very purpose. It uses an nRF24L series radio at its core, and adds functionality to switch the frequency automatically when the retransmit count is high. 

Best regards
Torbjørn