I’ve been developing a home made bike power meter and have something that mostly works, but the ANT communications seem to be a bit flaky.
I’ve just noticed that the suggested MISO and MOSI pins on the board are gpio 1.14 and 1.15 which are described as “Standard drive, low frequency I/O only” in the nrf52840 data sheet. I’m using those pins for SPI at 1Mhz (active for an 8 byte transfer once every 100ms).
Could this be causing interference? It seems strange that the board recommends those pins for SPI when they’re supposedly low frequency.
I’m mostly using vscode for development. It’s a SEGGER studio project using Nrf5 Sdk, but mostly I build using embuild, except when I need to use the debugger.
For the most part, ANT seems to be working; but I notice that there are short periods (up to about 10 seconds) where Garmin reports the power as zero when it clearly shouldn’t. And I’m recording per second data to the external flash on the board - so I can see that the device was trying to broadcast non-zero power during those times. I typically get one drop out like that every 15 minutes or so.
I’ve not been able to find a reason for this, so when I noticed the MISO/MOSI issue, I thought I’d ask.
As far as I’ve been able to determine, the only reason to restrict those pins to low frequency is to avoid RF interference. I’m just wondering if anyone has any experience of these pins actually causing a problem. If need be, I can redo my design - but that’s a lot of trouble if this is just a theoretical problem (or if I’ve misunderstood the data sheet). And presumably this was taken into consideration when picking those pins in the first place.