NR51422 radio not detected

[Darshan]

Hi

I have an custom board which uses an nrf51422 SOC. I am facing issues with my radio.I use an softdevice s110 with an application on it.

The code just works fine with the nrf51422-DK where I can switch ON/OFF an LED using an phone app.

But with the same code on my custom board I am not able to detect device. The program is running I have debugged all the stages

I measured the voltages near the antenna components on both the boards and they are the same. with three pulses of 1.9V and after capacitor its analogue signals with three pulses.

Components ordered as per BOM of nrf51422-DK

Please find the custom board PCB antenna below

nrf51422_custom_PCB.png

shematic.JPG

16Mhz_abracon.pdf

[Ole Bauck]

Is the code running at all? Do you use an external 32 khz crystal? The examples use this and if you don't have it, the code will be stuck in sd_softdevice_enable(...) waiting for the crystal to start. If you don't have external clock change the softdevice init call to this:

SOFTDEVICE_HANDLER_INIT(NRF_CLOCK_LFCLKSRC_RC_250_PPM_TEMP_4000MS_CALIBRATION, NULL);

I see some minor faults in the antenna design since you have not followed the reference design, but these should only degrade antenna performance, dont make it not work.

You may also want to change the pin definitions to match your custom board. Make a new file called custom_board.h with your pin definitions and change preprocessor definition BOARD_PCA10028 to BOARD_CUSTOM (see pca10028.h for how it is done for the DK).

Could you give us some more information like how the application is failing and maybe include the schematic and layout files in the post?

[Darshan]

Thank You

Like I have already said the code is working and I have debugged all the stages. There is no stuck up. Yes we do use an 32Khz crystal.

I have measured the antenna voltages as well. it seems like its pulsing. but I am not able to detect it

Please find the schematic in my above question.

Pin mappings are all the same from DK to our custom board.

[Ole Bauck]

You said that you used the DK BOM, but I see that you are using a through hole crystal. This may have different load capacitance and hence the capacitors need to be a different value. If these are the wrong value, the frequency of the crystal may be incorrect which will make the radio frequency incorrect. The accuracy of the crystal needs to be +-40 ppm for bluetooth low energy applications. What is the load capacitance (CL) and the accuracy of the crystal?

[Darshan]

The external 16Mhz crystal accuracy is around 20 PPM and load capacitance used is 12pF 5%. Instead Can we use the internal RC HFCLK oscillator ? So what changes should I make inside the code or its initialised inside soft device ?

please find the crystal data sheet in the question above.

[Darshan]

Thank You Ole Bauck for your help about the load capacitance.

I rectified the problem and I am able to detect the waves now. I increased the capacitance from 12pF to 24pF across 16Mhz crystal and its working .