Question about SPI2 using PC_2 and PC_3

[XLin.2]

My project (Stm32H753) has 2 identical external ADCs, one on SPI2 and one on SPI3. The one on SPI3 is working fine, but I am having problems with SPI2. The code for them are the same, except of course different 'hspi' and pin assignments.

The SPI is configured to use PC2 and 3 as MISO and MOSI, I probed SPI signals, everything looked fine except on MISO (ADC output) the voltage is only 1Vpp. Open the analog switches (SYSCFG->PMCR) didn't help much (instead reading all 0s, openning the switches gives all 0xfff readings. I have internal pullup for MISO).

Just curious, when PC_2 and PC_3 are labeled with '_', are there any special steps to use them for SPI2?

[STOne-32 · Accepted solution]

Dear @XLin.2 ,

You can check this Knowledge Base FAQ :

https://stcommunity.st.com/t5/stm32-mcus/faq-default-state-of-stm32h7-switches-connecting-pxy-c-and-pxy/ta-p/49300

_C pins are dedicated for a direct connection to ADC input stage, they are special with restrictions when used as Digital for SPI or any other peripherals such as current limitation - specified in the datasheet and Errata.

Ciao 

[XLin.2]

Thanks Ciao. I realized we are using 208 pin package which does have the same pads as 240 pins. We will assign other pins for the SPI.