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STM32F4-Disco Strange Glitches on SPI1

Question asked by terter etuet on May 4, 2018
Latest reply on May 6, 2018 by terter etuet

i have a STM32F4-Disco configured SPI1 / SPI2 as slaves to observe the in- and output of an external SPI-device (done with CD4021/CD4094 shift registers) and output something on SPI1 (MISO PB4) . SCLK goes to PB13 (SPI2 SCK), PB3  (SPI1 SCK) and as external Clock to TIM2 (PA15 TIM2_ETR) to count the Pulses. Annoyingly the Clock on SPI1 Glitches, and what is very strange, it only affects SPI1... TIM2 which Counts the pulses seems ok, also SPI2...

the SCLK is connected with a short wire between PB13/PA15/PB3, tried to Terminate after with 1kOhm to VCC&Gnd, doesent help...SPI_Clock glitch-SPI1 out (D4) of sync

D4 is the SPI1-MISO with a nice glitch on the 8th pulse, D3 is SCLK, D7 is the TIM2 OC3 signal after 8 Pulses,
D5 is SPI1 MOSI....

So the Input & Output of SPI1 are scrambled....


SCLK is ca 1MHz, and the Signal integrity dosent look bad...

And when this is happening, how do i reset SPI1? Disabling / Reenabling with



doesent Help.....

Many thanks for some Pointers!