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Having problems with SPI on .NET MF 4.3 Firmware?


Based on my logic Analyzer, it looked like I had noise in the SPI bus (see images). I figured I was doing something wrong, so I went back and had similar problems on my CerbuinoBee communicating with my Flash Chip Gadgeteer module with my 4.3 firmware loaded. Then I went back to the Release GHI firmware, and it worked perfectly. I am scratching my head at this point. I will probably repeat all this a few more times, but it looks like the SPI on the 4.3 firmware is somewhat unreliable. Anyone else notice this or is it just me and my crummy GCC compiling skills?

I am tempted to think that there is an internal resistor that is not set on MOSI or MISO with the 4.3 firmware… but I might be full of it…

P.S. I am sending the 0x9F command to the flash chip in both images, but I mixed up MOSI and MISO in one of them…


SPI uses a push-pull driver; there are no pull-up resistors. It looks like your slave device is also a bit noisy. I’ve never seen that before! Do you have good power supply decoupling on all the components?