nRF52832 BLE Beacon sample not working with external buck converter

[X4ce]

Hello,

I am developing a custom board using nRF52832 (QFAA) and flashed (no debug) it with sample beacon app (NCS) to check the transmission. When I power custom board using VDD & Gnd from nRF52840 DK, I can see the beacon packets on the nRF app but when I power it using on-board buck converter (TPS5430), I don't see any beacon packet on the app but it does when I revert power to nRF DK. Using buck converter, I see a voltage of 3.4V across the decoupling caps. Here is my nRF52832 schematic along with buck converter.

I will be grateful, if someone could shed their expert opinion/ suggestion on this issue.

Regards

Shahid

[Simonr]

Hi

Where are you supplying the board exactly when supplying it from the DK? Also, please check if the DCDCEN is set in your project, as that can cause some trouble when you don't have the components in your design, and we've seen that it only works when powered from a DK due to that in the past as well.

Best regards,

Simon

[X4ce]

Hi,

Thanks for your response.

I am connecting only 2 wires i.e. VDD_nRF & Gnd from DK to VDD_nRF & Gnd on the custom board, respectively. Using these two wires only my custom board transmits packets.

I am not using DCDCEN and have disabled it in Kconfig.

Thanks

[Simonr]

Hi

Okay, so as long as you have 3V or more over the test point from the buck converter you should be fine here. But please double check that the Buck converter is connected/soldered properly, as it seems very strange. The other thing it could be is that it outputs too little current and that the Ampere is to low, but that seems strange too.

Best regards,

Simon

[X4ce]

Thanks for reply.

I have checked voltage at all the decoupling caps of nRF and also Buck's LED at 3.4V is also working.

This is Buck supports 1A.

I am still unable to figure out what could be the issue.

Regards

[Simonr]

Hmm, this is indeed mysterious. Do you see this on one specific board or have you seen this issue  on more than one of these custom boards of yours? Did you also check that the soldering of the Buck converter is indeed soldered correctly. You can also measure the voltage over DEC4 from the nRF52832 to see if there's any activity there or not. 1A should definitely be plenty, so too low of a current is likely not it then.

One thing though, since you don't have an external LF clock on your custom board, have you remembered to set the LF clock source on the application you've flashed onto it to use either the RC oscillator or SYNTH as the 32.768kHz LF clock source. Please use the https://docs.nordicsemi.com/bundle/ncs-latest/page/kconfig/index.html#CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC config to set the LF clock source to the internal RC oscillator and try agian.

Also, just to make sure you actually see the custom board advertising when using the DK as a power source, run an eraseall/recover on the DK to make sure the flash on the onboard nRF is empty when supplying the external board. 

Best regards,

Simon