ESP32 Forum

The press releases for the ESP32 mention an SDIO peripheral, however I'm having difficulties finding out much more information than that. The most I've read is that the ESP31 is a SDIO slave device (ie. SDIO used for a host micro to talk to the ESP31), while the ESP32 would be a SDIO master device (SDIO used to talk to an SD card.) We're searching for a wifi module that can read/write to a SD card at a decent rate (SPI being too slow.)

Can anyone confirm how the ESP32's SDIO is/can be used?

What is the speed that you could get using SPI interface with an SD Card? The ESP8266 easily managed around 10 Mbits/s with HSPI... so the ESP32 can do the same (SPI hardware is almost identical on both)

The SPI bus can be clocked at 80MHz, so 10MByte/s is the theoretical max. It can also do 4-bit parallel reads/writes, so with that it should be able to shift 40MByte/sec in theory. It has DMA, so as long as you keep the buffers filled, you should be able to get pretty close to that theoretical maximum.

10M bits I meant. That's the max I could go. Over that, traditional SPI mode won't work as card has frequency limits of about 25MHz.