Place nRF52840-QIAA-D0 in custom board

[Doroana]

Hi,

We have developed a custom board. We can upload code using nrf52840 sdk-ble stack. We can read NRF_LOGS. However when we test with the ble_app_blinky that works fine with the dev kit, it doesn't do anything in our custom board. We have placed NRF_LOGS in all the functions and we read all the messages. So the code is not blocked in any part. But in the nordic app we can not see the advertising of our custom board.  

We think that we probably did some obvious error but don't know where.

The pdf has our schematic

Series-8-main.pdf

[Håkon Alseth]

francisco.colaco said:

Two prototypes exhibit identical behaviour.  Nothing is shorted at the antenna path.

Q1: How about other bluetooth examples? Do they also behave like this?

Q2: Do you have access to a spectrum analyzer? If yes; You can check if the device outputs on the correct frequency.

It might be that the crystal is loaded incorrectly, which will drag the frequency, resulting in the radio not operating on the exact frequency that you want it to.

Q3: Do you have the details of the crystal that you have mounted? I'm particularly interested in the "CL" value of your mounted HF crystal.

 

Kind regards,

Håkon

[francisco.colaco]

The crystal is 8pF, MCSJK-7E-32.00-8-10-60-B-10.  10ppm error.

At the oscilloscope there is effectively 8 periods every 250ns, measured between peaks, so the frequency seems to be correct.  Timing seems to be not an issue, at the least in what pertains to HF crystal.

Is there anything in sdk_config.h that I need to configure so that the radio works without VDDH or VBUS?

Thanks for your help.

[Håkon Alseth]

francisco.colaco said:

Is there anything in sdk_config.h that I need to configure so that the radio works without VDDH or VBUS?

 No, if the CPU boots, the radio will also be powered.

8 pF CL gives:

C = 2CL - Cpin = 2*8 - 4 = 12 pF, so your loading is correct.

francisco.colaco said:

At the oscilloscope there is effectively 8 periods every 250ns, measured between peaks, so the frequency seems to be correct.  Timing seems to be not an issue, at the least in what pertains to HF crystal.

Note that you're loading the crystal with your probe when testing this way. In most cases, this will give a incorrect load, thus a low amplitude and possibly incorrect frequency. If your probe has low capacitance, which it seems to do as your measurements are per the crystal spec, then it should work just fine.

 

Could you check these as well? With Q2, I mean the RF frequency output. These are the advertising frequencies that you should see:

Håkon Alseth said:

Q1: How about other bluetooth examples? Do they also behave like this?

Q2: Do you have access to a spectrum analyzer? If yes; You can check if the device outputs on the correct frequency.

Kind regards,

Håkon