NRF24L01+ Antenna matching

[gabbla]

Hi all,

in my custom board I'm using an NRF24L01+ as RF transceiver. The relevant part of schematic follow: (hi res => https://imgur.com/a/z4nQxXh )

The following components value changed during tune phase:

• c22=8,2pf RF
  
• c23=4,0 RF
• r21=0
• r22= c20 c21=OPEN
• L3= Short
• C18= 47pf RF

I'm using M310210 as antenna (datasheet => https://media.digikey.com/pdf/Data%20Sheets/Ethertronics/M310210.pdf )

The result: (hi res => https://imgur.com/a/4ZdtaZ0 )

However I cannot exchange data between two boards. If I connect the boards to a reference NRF24L01+ boards the communication works. The chip soldered on the board communicate correctly with the CPU, since I can read back the configuration.

Am I missing something?

[Kenneth]

It is odd if you custom boards can successfully communicate with a reference board, but not with each other. Do the communication works both ways with the reference board? Have you measured the frequency accuracy on a unmodulated carrier on customer boards?

Have you tried to readback configuration of all register of the nRF24L01 to check for any discrepancy? What is the detailed chip marking on the nRF24L01 on customer boards and reference board?

Kenneth

[gabbla]

Hi Kenneth,

my boards communicate only if I connect to each a dev board, this allowed me to check that my firmware is doing to right stuff. However, if I try to establish a communication between my board (with the above hw configuration) and another one (both connected or not to a reference board) nothing works. I will check the markings this evening and ask a colleague to perform the measure.

Gabriele

[gabbla]

Alright, I did some test and found that the board I was using can correctly TX/RX on channel 76, meanwhile the other one must be set on channel 78 to receive the data sent by the one set on channel 76. Weird. I assembled another board and can correctly receive data on 76,  however I can't send. I will do some measurement on Monday, but at this point the antenna should be correctly matched.

Gabriele

[Kenneth]

I wouldn't focus too much on the antenna here. A poor antenna will affect range, but not frequency. So I would rather have checked if you may have mounted the wrong component values on the load capacitors on the xtal or wrong decoupling capacitors etc.