2020-11-13 02:06 PM
I have a new board design that interfaces an STM32H743 to a uSD card using 1.8V I/O. The SD Card is powered by 3.3V, and the card I am using supports the LVS mode of SD. I'm having a hard time trying to get the card up and running, and my searches for specifications for how LVS is supposed to work have turned up nothing conclusive. Does anyone have a register setting procedure or a patch to use with the HAL libraries to get this SD Card to talk at 1.8V over the SDMMC1 port ?
2020-11-14 06:38 AM
I don't believe you can change the logic level associated with the SDMMC peripheral. You could put in a hardware level shifter, or run the chip at 1.8V, or live with 3.3V logic.
Seems like LVS is perfectly happy working on 3.3V logic:
https://www.sdcard.org/developers/overview/low_voltage_signaling/index.html
2020-11-14 09:23 AM
The STM32H743I-EVAL had a level shifting transceiver, not sure if NXP still makes it or not. Don't recall the lower voltage, but don't thing it was 1.8V
There may have been some examples where it negotiated Ultra cards into higher performance mode, and perhaps DDR modes, but I suspect significant effort would be required to clean it up and test to commercial grade.