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STM32F407-Discovery, VBUS/PA9 and SPI-Slave

Question asked by Soderhall.Mats on Apr 9, 2014
Latest reply on Apr 9, 2014 by waclawek.jan
I am using SPI2 as a slave with the help of DMA for fetching a stream with 16byte-burst of data. To test my application i have been looping many GB of data without any bit error so i am confident that my application is stable.
However, when i apply 5 Volts to GPIO PA9 the data i receive gets corrupt at random intervals.
PA9 is configured as digital input (and i tried with analog input, same result).

I have checked with an oscilloscope/logic analyzer and there is nothing wrong with the data sent to the SPI-slave.

If i apply 4.8 Volts to PA9 i can not reproduce the issue. If i apply 4.9 Volts i get about 1% error. At 5.0 Volts 50% of my bursts are corrupt and at 5.1 Volts 99% is corrupt.

I have tried this om three different boards with the same result.

Have anyone seen this issue or know about some way to solve it?