Handbuilt Core- Rapid Flashing after loading Bootloader

Hardware
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So I used a logic analyzer on the USBP, USBM signals on the STM32 chip pins and here is what I have. I should also note that for my board I was using the USB hardware from a Maple Mini directly connecting to my STM32 chip pins, this way I took my USB hardware out of the loop.

Compared to the Spark Core communication that works so effortlessly…

The data for the above screen captures is here , you will need the Saleae Logic Analyzer SW (free) to view it

@BDub, do you think my choice in caps for the 8MHz crystal would be causing the pulse widths to be different? (I ordered 18pF caps so will see if those make any difference when I get them)

1 Like
42

I believe the pulse widths may not look like they are matching, but it is because you are approaching the max sampling rate of the Logic and it doesn’t have enough datapoints to accurately display the pulse width. SInce it’s USB, it’s a differential signal so the waveform on D+ should be mirror image of D-. You can see it doesn’t even match on your known good Spark Core.

As far as timing, it looks like they are close enough to each other to work. It’s not way off or anything.