Advertisements on custom board slower than on PCA10040

RE: Advertisements on custom board slower than on PCA10040

potbhare — Wed, 11 Apr 2018 18:31:38 GMT

ketiljo I replaced the 12pF caps I was using with 16pF ones to match the spec that Nordic has laid out and the one custom board is advertising a lot faster. I think that did the trick. Thank you!

RE: Advertisements on custom board slower than on PCA10040

ketiljo — Wed, 11 Apr 2018 13:48:29 GMT

The 32 MHz have little influence on the timing, it's the 32 kHz crystal that does that.

If you are using a 32 MHz with a stability of 50 ppm, it's out of spec. BLE requires 40 ppm or better. This is the total stability (over temperature and initial tolerance plus aging).

What's the spec (tolerance and CL value) of the crystals (both) you're using? And what are the values of the load caps?

RE: Advertisements on custom board slower than on PCA10040

potbhare — Wed, 11 Apr 2018 06:03:05 GMT

The 32MHz crystal used has a frequency stability of 50ppm. I believe the PCA10040 has a crystal with 20ppm stability. I will update the config file to reflect our crystal. But does this make such a huge difference?

We have a custom desktop application with a USB dongle used to pick up advertising packets from our devices. I have several production devices using nRF51 which advertise at 200ms, phones which advertise at 100ms, and the new nRF52 board which should be advertising at 100ms as well. I see all the other devices at their respective advertising rates, except this one new board.

RE: Advertisements on custom board slower than on PCA10040

Susheel Nuguru — Wed, 11 Apr 2018 03:43:30 GMT

If the code is the same, then the big difference comes from the accuracy of the crystals you are using. You have to tell the BLE stack the correct accuracy in ppm of the crystals used.

What is the device that is receiving these advertising packets? is it another low power device or a sniffer?

I would recommend you to sniff the packets of the two devices separately. That is switch the other advertiser off when sniffing one. This is to make sure if the air traffic of the two devices look the same without interference from the other.