Custom boards not drawing enough current while advertising (programmable, PPK shows advertising state, but boards not discoverable in mobile app)

RE: Custom boards not drawing enough current while advertising (programmable, PPK shows advertising state, but boards not discoverable in mobile app)

Noah — Sun, 03 Jan 2021 06:05:23 GMT

Ultimately I think this is just an issue with PCB assembly, I'm ordering small batches of just 20-40 PCBs with a rather delicate 4 layer flex PCB design. About half of the boards work fine, the other half don't, so I think this just boils down to a yield problem. With more units, more investment into assembly fixturing and calibration, I think the yield will get better. The response is still helpful, thank you

RE: Custom boards not drawing enough current while advertising (programmable, PPK shows advertising state, but boards not discoverable in mobile app)

Noah — Fri, 01 Jan 2021 03:01:40 GMT

I will look into all the points you mentioned, thank you. What's interesting is how you mention the "good" current draw actually looks too high. I've probably tested close to 750 boards in total, across all my designs, and this 12mA spike is what I've seen across all of them during advertising. Maybe I never enabled DCDC in my firmware, haha I will double check!

RE: Custom boards not drawing enough current while advertising (programmable, PPK shows advertising state, but boards not discoverable in mobile app)

Stian Røed Hafskjold — Wed, 30 Dec 2020 10:48:43 GMT

Hi, are you able to zoom in on the advertising event, and compare the two plots. I think maybe you will have to use the bottom graph in the PPK software to get a good enough resolution. I was thinking if we were able to identify which parts of the advertising event that are consuming less current (if it's only TX, or both RX and TX, CPU etc), it should help us debug this further.

If you are using DCDC I think that the "good" plot has too high peak current consumption, even with 4 dBm output power the TX should not be higher than 8-9 mA. And with a 0 dBm output power the bottom plot looks normal. This is of course if nothing else is running at the same time. To me it looks like DCDC is not enabled?

Maybe you can try to flash a test FW where you both enable and disable the DCDC, and then check if the current consumption changes. Or if the failing boards are working when the DCDC is disabled.

Yes, a bad connection on DEC2 might cause problems, so maybe you can try to swap out the capacitor with a new one.

Are you able to measure the voltage on the decoupling caps? DEC1, 2 and 4? Preferably with a scope to see the ripples, and max/min voltages.