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@jijidad
Yes, I'm using MDBT42Q with 1v99 firmware. I'm using pins D14 and D15. Using D14 for the clock. I just restarted the board by disconnecting the battery and reconnecting. I'm now no longer getting the inverted mosi! I've tried for the last hour to reproduce getting that inversion back, but I haven't been successful yet. Any ideas on how it got into that state? Some internal pullup or something that didn't get reset? It probably would go unnoticed for most SPI situations since during the clock ticks, the voltage is correct. It's just in between the bytes that it goes high. But, after resetting, I'm not able to reproduce. Argh!! If you think that might be a bug somehow, I'm happy to try things that will help track this down if you want me to.
With more testing, I did catch something that I didn't catch before which might be causing the variability in the readings. There appears to be an intermittent variability in the gaps between the mosi bytes. Normally, it's 30uS, but sometimes it's much higher. Here are a couple of examples:
Notice that there can sometimes be over 100uS gaps. Have you run into this with software SPI? These longer gaps seem relatively infrequent. I'm wondering if this is causing the variability in the weight readings due to the ADC timing out or something. I haven't yet been able to correlate these two things though.
Sorry. I feel like this is muddying the water instead of adding clarity.