diff --git a/lib/main/STM32H7/Drivers/STM32H7xx_HAL_Driver/Src/stm32h7xx_ll_sdmmc.c b/lib/main/STM32H7/Drivers/STM32H7xx_HAL_Driver/Src/stm32h7xx_ll_sdmmc.c
index 8f08dbcf9..44a4ecba4 100644
--- a/lib/main/STM32H7/Drivers/STM32H7xx_HAL_Driver/Src/stm32h7xx_ll_sdmmc.c
+++ b/lib/main/STM32H7/Drivers/STM32H7xx_HAL_Driver/Src/stm32h7xx_ll_sdmmc.c
@@ -446,13 +446,13 @@ HAL_StatusTypeDef SDMMC_ConfigData(SDMMC_TypeDef *SDMMCx, SDMMC_DataInitTypeDef*
 
   // DC - See errata 2.11.4 - 8 SDMMC clock cycles must elapse before DTEN can be set.
   // 32U below is used as a VERY rough guess that the SDMMC clock is 1/4 of the sytem clock, 8 * 4 = 32 and that the
-  // assembly below only takes 1 CPU cycle to run. All of which will be wrong, but right enough most of the time, especially
-  // when considering other processing overheads.
+  // loop code below only takes 2 CPU cycles to run. All of which will likely be wrong, but right enough most of the time.
+  // It's important that the code isn't optimized-out by the compiler or linker too, see
+  // https://stackoverflow.com/questions/7083482/how-to-prevent-gcc-from-optimizing-out-a-busy-wait-loop
   register uint32_t count = 32U;
-  do
-  {
-    count--;
-  } while(count > 0);
+  for (unsigned i = 0; i < count; i++) {
+    __asm__ volatile("" : "+g" (i) : :);
+  }
   // DC - See errata 2.11.4
 
   /* Write to SDMMC DCTRL */
diff --git a/src/main/drivers/sdio_f4xx.c b/src/main/drivers/sdio_f4xx.c
index 888d7c51c..72466b5d3 100644
--- a/src/main/drivers/sdio_f4xx.c
+++ b/src/main/drivers/sdio_f4xx.c
@@ -1654,7 +1654,7 @@ bool SD_GetState(void)
 
 
 /** -----------------------------------------------------------------------------------------------------------------*/
-SD_Error_t SD_Init(void)
+static SD_Error_t SD_DoInit(void)
 {
     SD_Error_t errorState;
 
@@ -1704,6 +1704,22 @@ SD_Error_t SD_Init(void)
     return errorState;
 }
 
+SD_Error_t SD_Init(void)
+{
+    static bool sdInitAttempted = false;
+    static SD_Error_t result = SD_ERROR;
+
+    if (sdInitAttempted) {
+        return result;
+    }
+
+    sdInitAttempted = true;
+
+    result = SD_DoInit();
+
+    return result;
+}
+
 /** -----------------------------------------------------------------------------------------------------------------*/
 /**
   * @brief  This function handles SD card interrupt request.
diff --git a/src/main/drivers/sdio_f7xx.c b/src/main/drivers/sdio_f7xx.c
index f8a0427b5..84d2a5cd1 100644
--- a/src/main/drivers/sdio_f7xx.c
+++ b/src/main/drivers/sdio_f7xx.c
@@ -1637,7 +1637,7 @@ bool SD_GetState(void)
 
 
 /** -----------------------------------------------------------------------------------------------------------------*/
-SD_Error_t SD_Init(void)
+static SD_Error_t SD_DoInit(void)
 {
     SD_Error_t errorState;
 
@@ -1683,6 +1683,23 @@ SD_Error_t SD_Init(void)
     return errorState;
 }
 
+SD_Error_t SD_Init(void)
+{
+    static bool sdInitAttempted = false;
+    static SD_Error_t result = SD_ERROR;
+
+    if (sdInitAttempted) {
+        return result;
+    }
+
+    sdInitAttempted = true;
+
+    result = SD_DoInit();
+
+    return result;
+}
+
+
 /** -----------------------------------------------------------------------------------------------------------------*/
 /**
   * @brief  This function handles SD card interrupt request.
diff --git a/src/main/drivers/sdio_h7xx.c b/src/main/drivers/sdio_h7xx.c
index d069ad8b2..1511d4680 100644
--- a/src/main/drivers/sdio_h7xx.c
+++ b/src/main/drivers/sdio_h7xx.c
@@ -47,6 +47,9 @@ typedef struct SD_Handle_s
     uint32_t          CID[4];           // SD card identification number table
     volatile uint32_t RXCplt;          // SD RX Complete is equal 0 when no transfer
     volatile uint32_t TXCplt;          // SD TX Complete is equal 0 when no transfer
+
+    uint32_t RXErrors;
+    uint32_t TXErrors;
 } SD_Handle_t;
 
 SD_HandleTypeDef hsd1;
@@ -54,7 +57,7 @@ SD_HandleTypeDef hsd1;
 SD_CardInfo_t                      SD_CardInfo;
 SD_CardType_t                      SD_CardType;
 
-static SD_Handle_t                 SD_Handle;
+SD_Handle_t                        SD_Handle;
 
 typedef struct sdioPin_s {
     ioTag_t pin;
@@ -260,7 +263,7 @@ bool SD_GetState(void)
     return (cardState == HAL_SD_CARD_TRANSFER);
 }
 
-SD_Error_t SD_Init(void)
+static SD_Error_t SD_DoInit(void)
 {
     HAL_StatusTypeDef status;
 
@@ -516,6 +519,22 @@ SD_Error_t SD_GetCardInfo(void)
     return ErrorState;
 }
 
+SD_Error_t SD_Init(void)
+{
+    static bool sdInitAttempted = false;
+    static SD_Error_t result = SD_ERROR;
+
+    if (sdInitAttempted) {
+        return result;
+    }
+
+    sdInitAttempted = true;
+
+    result = SD_DoInit();
+
+    return result;
+}
+
 SD_Error_t SD_CheckWrite(void) {
     if (SD_Handle.TXCplt != 0) return SD_BUSY;
     return SD_OK;
@@ -615,6 +634,20 @@ void HAL_SD_RxCpltCallback(SD_HandleTypeDef *hsd)
     SCB_InvalidateDCache_by_Addr((uint32_t*)alignedAddr, sdReadParameters.NumberOfBlocks * sdReadParameters.BlockSize + ((uint32_t)sdReadParameters.buffer - alignedAddr));
 }
 
+void HAL_SD_ErrorCallback(SD_HandleTypeDef *hsd)
+{
+    UNUSED(hsd);
+    if (SD_Handle.RXCplt) {
+        SD_Handle.RXErrors++;
+        SD_Handle.RXCplt = 0;
+    }
+
+    if (SD_Handle.TXCplt) {
+        SD_Handle.TXErrors++;
+        SD_Handle.TXCplt = 0;
+    }
+}
+
 void HAL_SD_AbortCallback(SD_HandleTypeDef *hsd)
 {
     UNUSED(hsd);
diff --git a/src/main/msc/usbd_storage_sdio.c b/src/main/msc/usbd_storage_sdio.c
index 53c1487a2..8fd371b83 100644
--- a/src/main/msc/usbd_storage_sdio.c
+++ b/src/main/msc/usbd_storage_sdio.c
@@ -167,13 +167,17 @@ static int8_t STORAGE_Init (uint8_t lun)
     LED0_OFF;
 
 #ifdef USE_DMA_SPEC
-        const dmaChannelSpec_t *dmaChannelSpec = dmaGetChannelSpecByPeripheral(DMA_PERIPH_SDIO, 0, sdioConfig()->dmaopt);
+#if defined(STM32H7) // H7 uses IDMA
+    SD_Initialize_LL(0);
+#else
+    const dmaChannelSpec_t *dmaChannelSpec = dmaGetChannelSpecByPeripheral(DMA_PERIPH_SDIO, 0, sdioConfig()->dmaopt);
 
     if (!dmaChannelSpec) {
         return 1;
     }
 
     SD_Initialize_LL((DMA_ARCH_TYPE *)dmaChannelSpec->ref);
+#endif
 #else
     SD_Initialize_LL(SDCARD_SDIO_DMA_OPT);
 #endif
@@ -181,7 +185,7 @@ static int8_t STORAGE_Init (uint8_t lun)
     if (!sdcard_isInserted()) {
         return 1;
     }
-    if (SD_Init() != 0) {
+    if (SD_Init() != SD_OK) {
         return 1;
     }
 
diff --git a/src/main/startup/system_stm32h7xx.c b/src/main/startup/system_stm32h7xx.c
index 9c30ff74e..367f36253 100644
--- a/src/main/startup/system_stm32h7xx.c
+++ b/src/main/startup/system_stm32h7xx.c
@@ -596,6 +596,11 @@ void SystemClock_Config(void)
 
 #ifdef USE_SDCARD_SDIO
     RCC_PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_SDMMC;
+
+#if (HSE_VALUE != 8000000)
+#error Unsupported external oscillator speed.  The calculations below are based on 8Mhz resonators
+// if you are seeing this, then calculate the PLL2 settings for your resonator and add support as required.
+#else
     RCC_PeriphClkInit.PLL2.PLL2M = 5;
     RCC_PeriphClkInit.PLL2.PLL2N = 500;
     RCC_PeriphClkInit.PLL2.PLL2P = 2; // 500Mhz
@@ -606,6 +611,8 @@ void SystemClock_Config(void)
     RCC_PeriphClkInit.PLL2.PLL2FRACN = 0;
     RCC_PeriphClkInit.SdmmcClockSelection = RCC_SDMMCCLKSOURCE_PLL2;
     HAL_RCCEx_PeriphCLKConfig(&RCC_PeriphClkInit);
+#endif // 8Mhz HSE_VALUE
+
 #endif
 
     // Configure MCO clocks for clock test/verification