SDIO Interface Voltage

ivan.p · Posted at 9/29/2023 07:36:28

Last edited by ivan.p In 9/29/2023 07:42 Editor

Hi!

I have connected a WiFi module to Core-3308Y using the SDIO interface.

The module itself is detected as SDR50 device:

[ 3.329205] mmc2: new ultra high speed SDR50 SDIO card at address 0001

According to the SDIO standard, SDR50 mode uses 1.8v signaling.
I have looked at the interface levels by scope before and after the WiFi module detection, and in all cases they seem to be 3.3v, not 1.8v.

Which volatge is used by SDIO interface on Core-3308Y? Can it somehow be switched to 1.8v?

BTW The interface seem to work at 3.3v, but I had no chance to test the communication quality yet.

Firefly · Posted at 10/7/2023 16:52:02

Hello, please check this specification: https://download.t-firefly.com/% ... on.pdf?v=1696668643

ivan.p · Posted at 10/9/2023 07:10:58

Last edited by ivan.p In 10/9/2023 07:12 Editor

According to RK3308 datasheet, SDIO signals correspond to VCCIO4 domain. Its specified voltage is 1.8v. But it seems that on Core-3308Y VCCIO4 is fed by 3.3v by default.
The question is: could the voltage be somehow switched to 1.8v by software (gpio-regulator in terms of Device Tree)?

BTW the MMC interface has this functionality, as it is described in the module datasheet.

Firefly · Posted at 10/9/2023 10:45:37

ivan.p Posted at 10/9/2023 07:10
According to RK3308 datasheet, SDIO signals correspond to VCCIO4 domain. Its specified voltage is 1. ...

No, you can only turn on or off the I/O via software. Switching SDIO voltage needs to change the hardware.

[Hardware] SDIO Interface Voltage

【Hardware】 SDIO Interface Voltage