SDMMC init fails at SD_PowerON() with SDMMC_ERROR_CMD_RSP_TIMEOUT in STM32U575
Hi all,
My MX_SDMMC1_SD_Init() is failing and dropping into Error_Handler() on a custom STM32U575RGT6 board.
I traced it down to SD_PowerON() failing — it returns HAL_SD_ERROR_UNSUPPORTED_FEATURE. Digging deeper, this happens because one of the internal response-check calls (SDMMC_GetCmdResp1() / GetCmdResp2() / GetCmdResp3()) is returning SDMMC_ERROR_CMD_RSP_TIMEOUT (the CTIMEOUT flag gets set) — basically the card isn't responding to one of the commands sent during power-on/init.
i have checked HAL_SD_InitCard() clock divider formula where HAL correctly computes ClockDiv = 21 for 16 MHz kernel clock also measured SDMMC_CK on oscilloscope and getting 381.7 kHz which is within spec (≤400 kHz)
we have external pull ups at all pins of sdmmc
plus when i run on this fun SDMMC_CmdAppCommand i can see activity on CMD line but i didnt get any response on that line.
the clock i’m giving is HSE PLL1P to SDMMC clock mux which is 16Mhz final
