RT685 EVK (rev E) - LEDs powered by VLED dim after initializing the SD card

[dash]

I integrated the SD card fatfs code into my application and it works as does the rest of my code.

The only issue is once I initialize the SD card, LEDs D8 (blue), D9 (red), D10 (green) and D11 (red power) get dim. D8-D10 are powered by V_LED, D11 powered by VDD_TARGET. V_LED does not dip after initialization. It is still at 3.3V. I can remove the SD card after initialization and the issue is still present.

I have two Analog Devices codec boards running off of 5V on the Arduino connector.

Thanks,

Dan

[dash · Accepted solution]

Found the issue. The SD card voltage was being lowered to 1.8V in the driver.

I hacked the following to fix the SD card at 3.3V.

1) in /MIMXRT685S_Project/device/MIMXRT685S_cm33_features.h

change these definitions from 1 to 0

/* @brief Has SDR50 support (HOST_CTRL_CAP[SDR50_SUPPORT]) */
#define FSL_FEATURE_USDHC_HAS_SDR50_MODE (0)
/* @brief Has SDR104 support (HOST_CTRL_CAP[SDR104_SUPPORT]) */
#define FSL_FEATURE_USDHC_HAS_SDR104_MODE (0)

2) in /MIMXRT685S_Project/sdmmc/host/fsl_sdmmc_host.h

change from 

#define SDMMCHOST_SUPPORT_DDR50 (1U)

change to 

#define SDMMCHOST_SUPPORT_DDR50 (0U)

this comments out the following set 1.8V code /MIMXRT685S_Project/sdmmc/src/fsl_sd.c

#if SDMMCHOST_SUPPORT_DDR50 || SDMMCHOST_SUPPORT_SDR104 || SDMMCHOST_SUPPORT_SDR50
        /* check if card support 1.8V */
        if ((card->flags & kSD_SupportVoltage180v))
        {
            if ((card->usrParam.ioVoltage != NULL) && (card->usrParam.ioVoltage->type == kSD_IOVoltageCtrlNotSupport))
            {
                break;
            }

            error = SD_SwitchVoltage(card, kSDMMC_OperationVoltage180V);
            if (kStatus_SDMMC_SwitchVoltageFail == error)
            {
                break;
            }

            if (error == kStatus_SDMMC_SwitchVoltage18VFail33VSuccess)
            {
                applicationCommand41Argument &= ~SDMMC_MASK(kSD_OcrSwitch18RequestFlag);
                card->flags &= ~kSD_SupportVoltage180v;
                continue;
            }
            else
            {
                card->operationVoltage = kSDMMC_OperationVoltage180V;
                break;
            }
        }

[dash]

NXP did reply with a workaround in the case you want to run at a faster SD card rate (requires 1.8V), still have bright LEDs.

Yes, RT685 EVK REV E will have such an issue when LDO2_OUT is programmed from 3.3V to 1.8V. 

As a workaround for RT685 EVK REV E, you can cut the trace between JS13.1 and JS13.2, connect JS13.1 to JS16.  

[gusarambula]

Hello Dan,

Thank you for sharing your solution. I'm sure it will help other Community users.

Regards,
Gustavo