nRF5840 not advertising with DFU code

[Katie Newell]

Hi Nordic team, 

I am working on a custom board which contains a nRF52840 BLE chip.

The board advertises with 'Nordic Template' code but not with the DFU code. 

I program first the chip with the soft device 's140_nrf52_7.2.0_softdevice.hex' then with DFU code. I have used this code for over 2 years and never had an issue. But now it's no longer working. 

The board is in a development phase, we have so far 2 versions. The first version, the DFU code was working fine on it. It's not working on the new version. 

The components and the schematic are the same between the 2 versions. We changed the layout though for space constraints. 

Do you think this issue has anything to do with the new hardware? 

The nRF5840 chip is a HJ-840 see here datasheet.

Any thoughts?

Many thanks 

[JONATHAN LL]

Hi,

What layout changes? any new pins in use or other pins in use? or is the schematic the exact same still?

But you have confirmed that the new board works otherwise?

Have you tested more then one sample of the new revision?

Regards,
Jonathan

[Katie Newell]

Hi Jonathan, 

I presented this issue to the PCB manufacturer explaining that we were expecting the exact same hardware and we don't understand why our firmware no longer work on the new hardware. They came back and suggested to change the following soft device settings: 

NRF_SDH_CLOCK_LF_SRC from 1 to 0

NRF_SDH_CLOCK_LF_RC_CTIV from 0 to 16

NRF_SDH_CLOCK_LF_RC_TEMP_CTIV from 0 to 2

NRF_SDH_CLOCK_LF_ACCURACY from 7 to 1

After these changes, now DFU code works OK on the new board. I checked the settings in the Nordic Template and they are indeed set as the manufacturer suggested. 

Would you be able to help us understand what these parameters do? Does the need of calibrating the soft device differently as we used to do mean that our hardware changed somehow? Maybe you can point us to a documentation about this. 

Apologies for the basic questions - we are not experts in this level of the firmware. We outsourced writing the firmware.

Thank you for your help and understanding

 

Many thanks

[JONATHAN LL]

That is the settings for the crystal oscillator, so could be that the external crystal is not mounted correctly?

The settings are for changing the accuracy from 20 to 500 PPM.

Regards,
Jonathan

[Katie Newell]

Thank you Jonathan.

I will get in touch with the manufacturer and see what we can correct.

What are the correct settings to use?

Kind regards

[JONATHAN LL]

Both can be correct, but seems like for some reason the tighter accuracy tolerance you was using is no longer working. Could be that the crystal that you are using is not as accurate as the last one for the previous design.

So if there is no other issues then there is nothing wrong with using the values that the manufacturer recommended. 

Regards,
Jonathan

[Katie Newell]

Thank you Jonathan - much appreciated.