How to verify that the 32MHZ crystal is actually working (nRF52832?

[abdosalm]

I am using nRF connect SDK v2.9.0 with a custom developed board that looks like this:

I tried the 'Bluetooth LE LED Button service' sample as it's and noticed that nothing was working. I grapped my logic analyzer and hooked it up onto the 32MHZ but nothing is showing. I mean other functionalities like zepyrRTOS, PWM, GPIOs, I2C, etc...  are working successfully but not BLE.

does the nRF52832 have an internal clock through which it works by default and if so, how does it use the external clock. what is the first thing to debug?

this is the crystal I am using:

https://www.lcsc.com/product-detail/Crystals_YXC-Crystal-Oscillators-X322532MOB4SI_C9009.html 

and these are the schematics:

[JONATHAN LL]

Hi there, 

You can use the radio test sample to check if the radio works, you can select const carrier and sett 0 og +4dBm as output and then you should see something with an RSSI viewer. 

Or you can use this HEX, it just puts the device on constant carrier on channel 40 (2440MHz). 
8267.nrf52 carrier ch40 4dBm.hex



Open you can use the nRF52 DK as a RSSI viewer, 

This is what it would look like if you have just normal (office) background noise. 


And this is what it would look like if the radio is sending a constant carrier on the selected channel. 

It does not show if the 32MHz crystal is correctly loaded as the PPM is not really measurable this way, but it does show if there is something going on at least. 

See: https://devzone.nordicsemi.com/guides/hardware-design-test-and-measuring/b/nrf5x/posts/general-pcb-design-guidelines-for-nrf52-series 


Also we do HW reviews here so for future projects feel free to ask for a second pair of eyes to have a look at the design. 


Regards,
Jonathan

[abdosalm]

Hi Mr.Jonathan.

Sorry for the late reply but I used a spectrum analyzer to make sure there was a signal being transmitted and I actually could see some peaks temporarily in the 2.4 to 2.5 GHZ bandwidth.

However, the nRF52 BLE can be seen on my laptop but not via nRF connect app on my android mobile phone:

when I tried to connect to it via my laptop, it gave me an error and I can see from the logs on the nRF52 side these logs:

so the antenna is working but is there anything to be modified from the nRF Connect App side for such an error?

[Turbo J]

Check permissions.

If you can't scan BTLE stuff in nrf connect for mobile app on android, you don't have "coarse location" permission enabled.

Note that you can't see connected devices as they usually don't advertize at all.

[abdosalm]

The application already has all the permissions it needs:

[JONATHAN LL]

abdosalm said:

Sorry for the late reply but I used a spectrum analyzer to make sure there was a signal being transmitted and I actually could see some peaks temporarily in the 2.4 to 2.5 GHZ bandwidth.

This is not good enough, there are channels and specific frequencies so if there is an offset it might cause poor BLE performance ans it might just be bordering on acceptable results.

This might also be the reason why device only works with\shows up on some devices and not others as sometimes there is a similar offset on some devices that work in favor for them. 


Also its not just the antenna, its the whole RF performance we want to look at, so the clock and the emission, so maybe you could share what you saw on he spectrum analyzer?  Using the hex file i provided, as it will give a clear result that is easy to evaluate.

Regards,
Jonathan

[abdosalm]

Sorry for the late reply,

When you first replied above with the '.hex' file to be flashed onto the target. When I tried to do it via black magic debugger, the debugger gave me an error but I tried to do it again today with segger jlink and it was downloaded successfully. 

Unfortunately, I have damaged all of my UFL male PCB connectors and I have ordered some that are expected to arrive in 20 days, until then, I can think of nothing to do to debug my problem. once the connectors arrive, I will keep you updated on my problem.

[JONATHAN LL]

abdosalm said:

Unfortunately, I have damaged all of my UFL male PCB connectors

As long as the antenna works you should be able to get some results, as you see from the images i shared there is no need to use the UFL connector here,  so no ned to connect the two units.

Regards,
Jonathan

[abdosalm]

Got it.

But there still exists a small problem, should be the unit that's it to be connected to the RSSI app to have a tuned antenna which I don't have. That's why I have ordered the nRF52840 Module USB Dongle like in the image:

to use it as a packet sniffer, or don't I have to?

[JONATHAN LL]

We are only interested in seeing if the device works to some extent, even with a poorly tuned antenna you might still see something and could still get some range. But that we dont know, so the antenna might work fine. 

Also with the hex file i shared we are not looking to sniff packets, we only look at the transmitted signal, there is no data there. Only a continues wave. 

If  you have a nrf52DK and your custom board then that is enough to do the test. 


Regards,
Jonathan