[solved] SDMMC 1-line mode, free-up unused pins

[markwj]

I'm running the SDMMC in 1-line mode, so would like to free-up the unused pins for other functions. Specifically SD_DATA1, SD_DATA2, and SD_DATA3. However, after mounting the SD CARD, it seems the driver re-maps those pins to SDMMC and I can't access them properly in the UART driver I am trying to work with.

Symptom is that the UART simply doesn't work. If I comment-out the SDCARD initialisation code, the UART then works fine.

[WiFive]

Are you talking about the Arduino version? If so you should post in Arduino forum.

[markwj]

Are you talking about the Arduino version? If so you should post in Arduino forum.

No. Straight C code, using latest ESP IDF.

[WiFive]

Do you set host.flags = SDMMC_HOST_FLAG_1BIT and slot_config.width = 1 ?

[markwj]

Do you set host.flags = SDMMC_HOST_FLAG_1BIT?

Yes.

and slot_config.width = 1 ?

No

That fixed it. Best 1 line (pun intended) fix ever. Many thanks for the quick assistance.

So, code for 1 bit SDCARD is:

Code: Select all

    sdmmc_host_t host = SDMMC_HOST_DEFAULT();
    // this tells SD host to keep using 1-line bus mode
    host.flags = SDMMC_HOST_FLAG_1BIT;

    sdmmc_slot_config_t slot_config = SDMMC_SLOT_CONFIG_DEFAULT();
    // this tells the driver to only initialize 1 data line
    slot_config.width = 1;

With that in place, GPIO4 and GPIO13 work for me with uart.

P.S. This thread (from last year) seems relevant as well:
viewtopic.php?t=3091