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How to get started with STM32L452 SDMMC interface

Sid Price
Senior

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

12 REPLIES 12

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.

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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
Guru

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

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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.

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

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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.

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

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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.

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

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