nRF21540 does not work

[carefree]

I use nRF52840DK and nRF21540EK to develop BLE programs, and the program uses FLASH for BLE image storage, the program works well on the DK.
However, when I burned it into our own drawn PCB, FEM didn't seem to work (couldn't search for the device I wanted to connect to).

We tried to find out if nRF21540 was the cause, however when we burned another BLE program, the FEM was working correctly (broadcast device).

3146.code.zip

This is a program that doesn't work。

1385.Code1.zip

This is the test program.

[Priyanka]

Hi,

Since your FEM seems to be working with a code and not with another, it could be that the problem is with the BLE code? 

Could you confirm whether code or code1 is the BLE program that doesn't work?

Regards,

Priyanka

[carefree]

Add:
1: In addition to the above differences, our PCB will use a separate IO to power on the nRF21540.
2: It can be used on the DK because the antenna of the DK itself works, not the nRF21540

[Priyanka]

Hi,

carefree said:

1. --[This program can't use FEM]--
MCUBOOT --> MAIN [Mount Little FS --> Start USB UART --> Power on FEM --> Check DFU mode --> Enable BLE]

Since this has more steps in the process, for diagnosing which part causes the issue, you could try to modify the program to bypass certain initialization steps (e.g., mounting LittleFS or checking DFU mode) and see if the FEM starts working. So this can help us isolate to which part causes the issue.

Also make sure that the FEM is properly set up or configure for the receive mode, i.e. you could recheck the control logic.

-Priyanka

[carefree]

After checking: the initialization seems to be OK, because I can see BLE is on in real time and scanning the peripheral devices. At the same time, I connected the logic analyzer and saw TX, RX, PDN working normally (I use GPIO control mode).

[carefree]

The Bluetooth extended broadcast I used seems to be able to search the signal even if the nRF21540 is not working, but even then, the nRF52840DK can search for the device through its own antenna, while our PCB can only search for other devices, but not the specified device.

[Priyanka]

Is it possible to share the schematics of your custom PCB?

-Priyanka

[carefree]

I think I have found the reason for the problem. Since I used Bluetooth extended directional broadcast, my transmitter should turn off or change the host address of directional broadcast. However, in my test, I set it to the DK board, so that the rest of the PCB could not be searched for connection.

After the problem is solved and solved, the function of nRF21540 is normal, which is verified in the signal quality detection of nRF21540 opening and closing.

Thank you very much for your help.