ESP32 Forum

Dear *,

we want to use ESP32-WROOM-32D module in our design.

The ESP32-WROOM-32D module is the Slave and uP is the host.

We want to interface the ESP32-WROOM-32D module to host uP via SDIO interface. Can this be done?

Please can you tell us which IO pins from the ESP32-WROOM-32D module should we connect to the host uP?

Also can you tell are all SDIO signals on ESP32-WROOM-32D module 3.3 voltage level?

Best Regards.

Yes, please check https://docs.espressif.com/projects/esp ... slave.html. Pins are 2,4,12-15, voltage level is 3.3V. Also make sure to understand https://docs.espressif.com/projects/esp ... ments.html before proceeding with the hardware design.

Hi ESP_igrr,

thank you for the links.

I have been reading trough the documentation, and found out that the flash voltage level in the ESP32-WROOM-32D is 3.3V and thus the strapping pin GPIO12 ( MTDI) has to be pulled low outside the module to set the VDD_SDIO to 3.3V, and this is incompatible with the SDIO slave specification because the SD_DATA2 needs to have a 50k or stronger pull-up.

1) One option is to use the bigger ESP32-WROVER module because it has internal pull-up on GPIO12.

2) The question is what kind of flash IC are you assembling in the ESP32-WROOM-32D, because some of the flash can work from 1.8V to 3.3V eg. Macronix MX25R3235FM1IH0 (32Mbit) or MX25R6435FM2IL0 (64Mbit)

(http://www.macronix.com/Lists/Datasheet ... 20v1.6.pdf)

and then we can use pull-up on ESP32-WROOM-32D

3) option is to use some logic so that when the strap pin are read the GPIO12 has a pull-down , and when used as SDIO slave it has a pull-up. For how long after the reset the GPIO12 has to be a pull-down for the strapping to sample the right value ?

Did you do maybe some test with this kind of configuration?

4) An other question, we can normal send the data from our host to ESP32 salve via SDIO? then the data will be handled with DMA and outputted through WiFi ?

5) Regarding Blue-tooth, what uart pins are used for the blue-tooth? And what uart pins are used for firmware flash uart and debug uart ?

Best Regards.