Can not find the device

[nine-fox]

Hi,

I am working on a custom design for NRF52832. The schematic and pcb layout are as follows. However, it seems that I can not get the signal working correctly. Would you please take a look and give me some tips/advices/suggestions? Thank you very much.

The custom board is just for a small keyboard which is space limited. For testing, I am using pcb antenna only. I soldered 2 boards and both of them have the same problem:

1. Use SWD to burn softdevice and hrs sample(removed the external LFCLKSRC and turned on RTT logging)

2. It doesn't show in nRF connect/toolbox

3. I tried other samples like hid_keyboard, still the same problem: It doesn't show in nRF connect/toolbox/iOS/android.

4. No any errors prompt in RTT logger.

I suspect this is a pcb antenna design issue. However, by reading a lot from infocenter, still I can not find what the problem is. Should I solder a shunt capacitor in C76?

According to the guideline here: devzone.nordicsemi.com/.../ I am using:

1. X7 = 32M crystal, load cap = 10pF

2. C79=C78 = 16pF

3. nRF52832-QFAA, 2 layers, 1.6mm thickness, and FR-4 dielectric.

4. To avoid side effects, all other components like LEDs are not soldered in my testing boards.

(Left side is Back copper layer and right side is the Silk layer)

My Dev environment: Windows 10, Jlink 5.12f, SDK 13.0.0. Please let me know if you need further information. Thanks very much.

Yours sincerely,

Vincent

[RK]

yeah he already said he did that.

[nine-fox]

hi guys, thanks very much for your comments. Still I cannot get it working...I will try the following things:

1. buy chip antenna and have a try
2. probably load caps are incorrect. I will buy again from another store
3. redesign the antenna layout

I will post when I have further info

[nine-fox]

Hi Turbo, thanks for your answer. As I mentioned in questions, I removed the external crystal.

Also my code（thats 99% sample code） works quite well in Development board

[AmbystomaLabs]

The chip antenna isn't going to help out your problem. Your layout for the chip antenna is poor compared to the F hybrid. If the nRF is working you should be able to pick it at close range.

On the load caps, what I meant is that I believe 16pF is the wrong value. I reviewed the Nordic guidance and it didn't address the parasitic capacitance of the circuit. This will change the load caps by a few pF.

Do you not have just an oscilloscope to measure the frequency of the 32MHz with?

If you go through a re-design, you have very significant problems with your ground plane. It is broken in most areas under the nRF. This alone could cause the nRF to be unstable and not transmit.

Also, your schematic shows that you split the power and RF grounds. This is wrong for this device.

Happy to continue helping. But you are going to need to do a little testing a provide a little more feedback.

[RK]

@nine-fox AbystomaL is probably right as usual. One way, if you have any kind of signal analyzer (if you don't, get one) to check the crystal frequency is to write some code to output the TIMER clock divided down to 1MHz or something like that and use the signal analyser to measure it. Measuring it directly with an oscilloscope is tricky as the leads have capacitance so you have to switch out the load caps to compensate for that. You do certainly have some ground plane issues, it's swiss cheese on both sides of that board. I will say what Nordic would say if they reply, start with the reference design and don't deviate from it :) I did deviate from it but only because I can't hand solder 0402s (actually I can but it takes a long time). I wouldn't toss your board and buy new bits yet, you have something which runs, write some test code and test what you have until you know what's wrong.