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electro-smith / libDaisy

Hardware Library for the Daisy Audio Platform
https://www.electro-smith.com/daisy
MIT License
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SD Card does not initialize 100% of the time #241

Closed hammondeggs closed 3 years ago

hammondeggs commented 4 years ago

Currently, with an "older" Kingston 8GB SDHC card (model SDC4/8GB 07), I am noticing that the card is not recognized every time on powerup.

In per_sdmmc.cpp, at SdmmcHandler::Init() , we see a couple lines:

    //hsd1.Init.ClockDiv = 168; // 476.2kHz works    
    hsd1.Init.ClockDiv = 6; // 12MHz works

I un-commented the 476KHz clock divider and commented out the 12Mhz clock div, rebuilt libdaisy and sure enough, the card appears to initialize every time.

Now, I know that a 476KHz SD card read speed isn't ideal (although for what I'm currently doing it's perfectly fine), so there likely is a happy medium here that would probably have to be deduced via some testing with different cards etc.

(FWIW I had a look at the traces on a scope, at 12mhz they're square enough but there appears to be some ~12MHz noise on the high level of the signal, not sure if this is related to this issue).

upbeat27 commented 4 years ago

If I remember correctly there is a bug in the STM32H7 HAL where it doesn't run at a lower clock when initializing the SD card, which is necessary to meet the spec. It was a long time ago, but I wouldn't be surprised if ST still have not fixed it.

stephenhensley commented 4 years ago

I think I had noticed this occasionally as well, but most of the time it was by trying to mount the card while Audio, and other high-priority interrupts had been enabled.

I remember the same bug as @upbeat27, but I believe it was fixed in one of the (semi)-recent HAL updates. Looking at the HAL, it seems to boot up the SD card at a fixed rate 476kHz, and then, updates the prescaler to the user defined value after initialization (might be worth actually verifying this, though).

I spent a good chunk of time last week with the SDMMC peripheral on the H7. I'll be updating the driver here a bit later this week. I was able to get it running with STs DMA template , and working up to 50MHz (I did not test writing w/ DMA or at the higher speeds yet).

stephenhensley commented 3 years ago

In addition to the above, it was pointed out that changing the GPIO_InitStruct.Speed value to LOW helps with the stability. We'll change that while reworking the rest of the driver.

stephenhensley commented 3 years ago

this should be resolved with the merging of #311

There is a note in there about the GPIO speed, and I can open another PR that adds that to the config.