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SPI2 with DMA sees CRC errors

Question asked by s.gd on Jul 13, 2011
Latest reply on Jul 14, 2011 by s.gd
I am repetitively sending/receiving 6 byte messages plus 16-bit CRC full duplex using SPI2 using DMA to/from another identical STM32 eval board with the same 72Mhz processor.  I am transferring at 9Mbps rate. However, about 3 to 4 Percent of the transaction fail due to CRC error. Going slower seems to make it worse. No other DMA activity is occurring. Setting DMA priority to "very high" made no difference. Any idea what to look for or try to eliminate the CRC errors?

Also, I can enable the same test using SPI1 and I never see CRC errors unless I force them by changing the polynomial on one end. The wiring between the boards appears identical. (I am also using the same baud rate on SPI1 by using a larger clock divisor since it is driven by 72Mhz pclk while SPI2 has 36Mhz pclk.)

Also, the SPI signals have the correct timing when I look with a scope.

-g

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