spi

[teijo]

Hi,

I have problem with SPI data transfer on stm32h743VIH. Spi is used with external ADC.

ADC data ready voltage level seems OK ~1,8 V (Vdd) but the MISO line shows only about half of this ~0,9 V. This seems to be too low for data transfer. MISO line is direct line to CPU.

STM provides master clock at 27MHz and SPIclk is 27 MHz from same source. MOSI is not in use.

Are there any configuration options that could explain this behaviour?

[Tesla DeLorean]

Prior Thread https://community.st.com/s/question/0D53W000004GxQcSAK/peripherals-not-working-below-3v

[Tesla DeLorean]

Chip Select?

It would help a whole lot if you provide a Data Sheet, Part# or link for the "External ADC", because it's the device generating the MISO signal.

[teijo]

Hello

We made a test by cutting the MISO line. It seems that the ADC MISO is correct level when it's not connected to CPU. So something on CPU side is pulling down or limiting the voltage.

Then when ADC MISO line cutted we try to use MISO line GPIOC pin2 as output with pull-up and the signal levels are at about 0,9 V level. While doing the same with GPIOE pin4 we have correct signal levels about 1,8 V. We are wondering if this is somehow related to different domains (D1, D2, D3) or power management in general. SPI2 (GPIOC pin2) is in domain 2 and GPIOE pin4 domain 3.

[teijo]

Help is still needed.

All tests now done with nothing connected to PC2_C pin. We cannot get is to correct voltage level. With brand new board with only PC2_C pin configured as GPIO and toggling provides voltage levels 0 - 0,9 V measured with oscilloscope. While testing this on same code on PA1 everything works properly voltage level is 0 - 1,8 V. Then next test with PC3_C and we get the same results as with PC2_C. So the pins PC2_C and PC3_C behave differently than PA2. Supply voltage is 1,8 V.

We did more tests when we found this thread https://community.st.com/s/question/0D50X0000AxFsTqSQK/stm32h743z-lqfp144-gpio-not-working-on-pc2c-and-pc3c

in our case we have LQFP100 so there is no analog switch but PC2_C and PC3_C seems to be connected to analog system. We tried changing the analog switch to HAL_SYSCFG_AnalogSwitchConfig(SYSCFG_SWITCH_PC2, SYSCFG_SWITCH_PC2_CLOSE); but it does not seem to have any effect.

In our design whole analog system is not powered and we getting a feeling that this a source of this problem but we would really need a confirmation before making a redesign.

All ideas are welcome.

Could some one confirm is the PA2 connected to analog system since in RM0433 Rev 7 is mentioned PA2_C but only PA2 is visible in DS12110 Rev 7. Then we could confirm that problem is only related to pins connected to analog system.