nRF52832 Custom Board Development Issues

RE: nRF52832 Custom Board Development Issues

ketiljo — Wed, 17 Oct 2018 13:18:19 GMT

Remember that the value of the load capacitors must match the crystal. The Murata XRCGB32M000F2P10R0 is a 6 pF crystal, so the load caps must be 8.2 pF each. Using this part number isn't necessary for correct operation, but using a crystal within the spec and with the correct load caps is needed.

No idea why it doesn't always work. Check the soldering.

The blinky example doesn't use the external crystal, only the internal RC oscillator. The radio will _always_ request the crystal oscillator to be started.

RE: nRF52832 Custom Board Development Issues

KaranRaj — Fri, 12 Oct 2018 11:14:10 GMT

Hi Ketiljo,

Sorry about the delay. I've been having some difficulties with logging in on the devzone.

So the nRF52832 chip is now responding after we changed the crystal to the Murata XRCGB32M000F2P10R0 (Nordic confirmed) 32MHz crystal. However, this does not clear my doubt of what exactly was causing the issue. And since we will be going into mass production soon after the development is finished, we need to make sure we leave no loose ends which might backfire later. I hope you understand.

Some points I'm unable to understand:

1. I had replaced the crystal with another part before(different part number) and the nRF52 still didnt respond. Why would it respond to only this particular Murata crystal?

2. When I replaced the crystal in the working board with the crystal from the non-working board, the board still responded. If the crystal was defected, the working board would stop responding right?

3. Why 3 of my custom boards would respond, whereas the other 3 would not?

4. The 3 working boards were responding with the "blinky" code even without any crystals connected to the nRF52832. I understand this must be because of the internal crystals but if it is the case, shouldnt it also work when the crystal was defected?

Best,

Karan

RE: nRF52832 Custom Board Development Issues

ketiljo — Tue, 25 Sep 2018 13:00:40 GMT

I've taken a second look, and except for the before mentioned R14 and R15, it looks correct.

RE: nRF52832 Custom Board Development Issues

KaranR — Tue, 25 Sep 2018 06:01:10 GMT

Yes, we have been continuously checking for soldering errors and changing components to spot the problem. Could you please verify the schematic and see if any component values are incorrect? (other than the R15 and R14) Maybe any components need to be removed or added that we are missing out on?

Thanks

RE: nRF52832 Custom Board Development Issues

ketiljo — Mon, 24 Sep 2018 13:12:06 GMT

Are you able to program and run the blinky example on some of your board? If so, you need to start looking for solder issues, incorrect components etc.

RE: nRF52832 Custom Board Development Issues

KaranR — Mon, 24 Sep 2018 07:09:49 GMT

Hi Ketiljo,

We removed R15 and set R14 to 0R as you suggested, but still didn't get any response from the nRF52832 chip even after re-flashing. Could you kindly suggest further?

Thanks

Regards

Karan

RE: nRF52832 Custom Board Development Issues

AmbystomaLabs — Thu, 20 Sep 2018 17:48:14 GMT

I think you should re-read your schematic. As Ketiljo pointed out R14 should be zero ohms and R15 should be removed.

It is completely wrong to have R14 and R15 even part of the circuit. Looks like you made a mistake. Having them there will keep the 32MHz oscillator from starting since the circuit will be stable. No telling what it will do to the internal RC oscillator. It could easily keep that from running properly since some of the clock buffers and inputs are likely common inside.

RE: nRF52832 Custom Board Development Issues

KaranR — Thu, 20 Sep 2018 14:43:43 GMT

Hi ketiljo,

Thanks for the prompt reply.

I will go ahead and try your solution, and see if it helps. Will get back to you soon with the results.

About the crystal, I have attached the datasheet for the crystal I'm using. The datasheet reads Calibration Load Capacitance as 8pF. So with your formula, Ccap should be 12pF, which is the ones I'm using. And for the "blinky" example, external crystals are not even required, am I right? I have tested this with my working board and it flashes, and gives the right output even without both LFXO and HFXO. Whereas my non-working boards dont respond even with the crystals.

devzone.nordicsemi.com/.../FL3200037_2D00_1129659.pdf

Thanks again.

Regards,

Karan

RE: nRF52832 Custom Board Development Issues

ketiljo — Tue, 18 Sep 2018 14:03:30 GMT

1. The schematic looks correct, except for the crystal oscillator. Remove R15 and set R14 to 0R and see if this helps.

Also check if the value of the load capacitors matches the CL value of the crystal (see the crystal spec). The formula is Ccap = 2 * CL - Cpin, where Cpin is 4 pF. Round down to the nearest available value. 10 pF caps are correct for a 8 pF crystal.

2. The crystals are not needed when the flash is programmed.

3. See #1.