How to get started with STM32L452 SDMMC interface

[Sid Price]

I am trying to use the STM32L452RE Nucleo to research an interface to an eMMC device. I have generated a project for this using STM32CubeMX. The eMMC device I am using has its interface voltage connected to 3V3, however, when I look at the CLK output from the STM32L452 I see a high voltage of only approximately 1.7V after the SDMMC power is enabled.

Is there a getting started guide for this MCU SDMMC interface?

There does appear to be a way to tell the SDMMC to use the 3V3 interface voltage, how can this be done?

Thank you,

Sid

[Tesla DeLorean]

Should be at whatever voltage you're running the L4

Some of the L4 have a bank G you can run at VCCIO, but that doesn't include the SDMMC pins.

At low frequency I'd expect this to go rail-to-rail, at high frequencies going to depend on scope and probe.

[Sid Price]

The L4 is powered with 3V3, right after the SDMMC is enabled the output voltage on the clock pin, for example, goes to 1.7V

Sid

[TDK]

How exactly are you measuring the 1.7V? Do you have a scope trace that you can show?

[Sid Price]

I have a scope probe on the clock output, right after the power is enabled (MCU on breakpoint after it) the voltage drops from 3V3 to 1V7. I do not see a clock signal, just a DC voltage.

[Tesla DeLorean]

Will have to scope a board here when I get a chance..

[Sid Price]

Do you have any links for reference material for this, an app note or something. I found an H7 app note but it is a different peripheral.

[TDK]

Are you sure it's fully initialized? You should see a constant square wave clock when it starts, not just a DC voltage.

[Sid Price]

I assume it is, I am using the L4 HAL and code generated by STM32CubeMX. What more than generate the project do I need to do in order to see the clock?

The clock config in CubeMX is happy.

[Tesla DeLorean]

I have working eMMC demos on the L4/L4+ platforms, are you in the market for such?

Dig thru this, did have it working on the Nucleo-L452RE

https://community.st.com/s/question/0D50X00009sVV1FSAW/stm32l4-sdmmc-standalone-mode-no-rtos-works-polled-not-with-dma