nRF51822 bonding failed

[Yi Su]

Hi,

I have a custom board with nRF51822 chip on it and tried to run the proximity sample program on it. I have used the nRF51822 develpment board + nRFgo Motherboard to tested my code and everything worked fine. BTW I am using SDK version 4 and softdevice s110_nrf51822_5.2.1. After that, I downloaded the same code to the custom board, it was broadcasting ok, I could see it from the proximity demo program, but when I tried to connect it, it showed: bonding... bonding failed. I attached the schematic and the screenshot of bonding failure error below. Can anybody help me figure out the problem? Thanks!

log after change crystal.txt

log before change crystal.txt

[Hung Bui]

Hi YiSu,

Could you try using the nRF Master Control Panel for testing ? There is a log file that might be useful to find the issue.

Your antenna might not be tuned and may limit the range of the RF.

Could you send me know the 16MHz crystal you use on your custom board ?

[Yi Su]

Thank you for the quick response. After I posted this question, I found an older post with the same problem and he solved the problem. According to your answer in that post, I noticed the load capacitance for both crystal are not proper. I use 425F35B016M0000(CTX804CT-ND) for 16MHz crystal and ABS07-32.768KHz-T(535-9542-1-ND) for 32kHz crystal. I calculated the right load capacitance should be: 22pF for 16MHz and 21pF for 32kHz. But I need to order those capacitors so I tried first with replace the 16MHz crystal with one in the development board. But it still couldn't bond. Now I don't know if it is the same problem with the older post.

[Hung Bui]

Hi YiSu,

Have you tried to use the 32kHz RC instead of the 32kHz crystal ?(by using for example NRF_CLOCK_LFCLKSRC_RC_250_PPM_4000MS_CALIBRATION in SOFTDEVICE_HANDLER_INIT())

Could you send me a close up photo of your board ? Have you tried with our stock SDK example or only with your firmware ? Could you try with other example, such as ble_app_hrs.

Do you have the same issue all the time when using Master Control Panel ?(connection BTLE_CONN_FAILED_TO_BE_ESTABLISHED )

[Yi Su]

Hi Hung Bui,

Thank you for your suggestion. It seems the 32kHz crystal is not working properly in my custom board. I tried to use the 32kHz RC, and the board bonded and was able to transmitting data.