nRF52832 High Frequency Clock selection

[josh]

I've spent some time searching and haven't found a definitive answer or anything obvious in the code. I'm developing the firmware for my application on the nRF52 DK, which looks like it has an external oscillators for the LF and HF clock. The module I'm using in the actual product only has an external oscillator for the LFCLK source.

What do I need to do to insure my firmware will work on the target board, using the internal HF clock source? I've searched the documentation and haven't found the answers...

Thanks, Josh

[RK]

Rather unlikely that any module only has an LFCLK source, without an HFCLK source you can't use bluetooth. So perhaps you want to go check that again.

And a search in the forum questions for 'LFCLK softdevice' will throw up at least 2 messages a week telling you what needs to be changed if you don't have an LFCLK to make bluetooth run. IT's also documented in the softdevice enable call.

[josh]

Yes, I am aware that there are many threads discussing the LFCLK source, I had to sift through them when trying to find an answer about the HFCLK. Maybe I made a mistake with the module I choose, per the documentation they only provide an external LFCLK. Perhaps they are expecting the host PCB to provide the HFCLK, but that seems a bit strange, they don't mention the need for this in their (skethcy) documentation. Here is the documenation for the module.

When I try to bring up my application on the module, which I have verified on a nRK5 DK board, it goes off the rails when it tries to enable the SoftDevice...I'm guessing this is because there is no external HFCLK. From the nRF5832 product spec it states that there is an internal HF oscillator, but it sounds like this can only be used while waiting for an external crystal to start up...am I interpreting this correct?

[RK]

you should go look at the documentation again as it clearly tells you the main crystal is integrated on the board and even mentions the 32MHz. There's no LFCLK, they just provide a connection for you to add your own, you can see that on the pinout. Not only that they also tell you for low power operation to add one and that's shown in their suggested schematic.

So you have an HFCLK and not and LFCLK which is why y9our board doesn't start, you have to change the startup to use a different LFCLK source, as mentioned in all the LFCLK messages you found earlier.