Dear expert,
My customer use SPI for communication between two F280039. Here is their test result:
1)Master DSP communication separate, slave DSP pin does not respond, MOSI pin communication waveform is normal, the waveform of non-communication period is also ok(default level is high).
2)Master DSP communicates with slaver DSP through SPI, the slaver DSP controls the MISO pin to respond, tests the MOSI pin communication waveform is normal. But the waveform of he MOSI pin is abnormal during the non-communication period. The level is not fixed, it will jump. Waveform of the MISO pin during communication and non-communication period is always normal.
They try to modify the pull-up resistant of MOSI、MISO、STE pin into 20k, and also try to delete the resistant, but it does not work.
Figure1 master pin:
Figure2 slaver pin:
