diff --git a/firmware/hw_layer/mmc_card.cpp b/firmware/hw_layer/mmc_card.cpp
index 923af208cf..d087ddc4c1 100644
--- a/firmware/hw_layer/mmc_card.cpp
+++ b/firmware/hw_layer/mmc_card.cpp
@@ -355,53 +355,67 @@ static const scsi_inquiry_response_t scsi_inquiry_response = {
 #endif /* HAL_USE_USB_MSD */
 
 /*
- * MMC card mount.
+ * Attempts to initialize the MMC card.
+ * Returns a BaseBlockDevice* corresponding to the SD card if successful, otherwise nullptr.
  */
-static void MMCmount(void) {
-//	printMmcPinout();
-
-	if (isSdCardAlive()) {
-		scheduleMsg(&logger, "Error: Already mounted. \"umountsd\" first");
-		return;
-	}
-	if ((MMCD1.state == BLK_STOP) || (MMCD1.state == BLK_ACTIVE)) {
-		// looks like we would only get here after manual unmount with mmcStop? Do we really need to ever mmcStop?
-		// not sure if this code is needed
-		// start to initialize MMC/SD
-		mmcStart(&MMCD1, &mmccfg);					// Configures and activates the MMC peripheral.
+static BaseBlockDevice* initializeMmcBlockDevice() {
+	if (!CONFIG(isSdCardEnabled)) {
+		return nullptr;
 	}
 
-	#if HAL_USE_USB_MSD
-		msdObjectInit(&USBMSD1);
-	#endif
+	// Configures and activates the MMC peripheral.
+	mmcSpiDevice = CONFIG(sdCardSpiDevice);
+
+	efiAssert(OBD_PCM_Processor_Fault, mmcSpiDevice != SPI_NONE, "SD card enabled, but no SPI device configured!", nullptr);
+
+	// todo: reuse initSpiCs method?
+	hs_spicfg.ssport = ls_spicfg.ssport = getHwPort("mmc", CONFIG(sdCardCsPin));
+	hs_spicfg.sspad = ls_spicfg.sspad = getHwPin("mmc", CONFIG(sdCardCsPin));
+	mmccfg.spip = getSpiDevice(mmcSpiDevice);
+
+	// We think we have everything for the card, let's try to mount it!
+	mmcObjectInit(&MMCD1);
+	mmcStart(&MMCD1, &mmccfg);
 
 	// Performs the initialization procedure on the inserted card.
-		LOCK_SD_SPI;
+	LOCK_SD_SPI;
 	sdStatus = SD_STATE_CONNECTING;
 	if (mmcConnect(&MMCD1) != HAL_SUCCESS) {
-		
-		#if HAL_USE_USB_MSD
-			// mount a null device to USB
-			msdMountNullDevice(&USBMSD1, &USBD2, blkbuf, &scsi_inquiry_response);
-		#endif
-
 		sdStatus = SD_STATE_NOT_CONNECTED;
 		warning(CUSTOM_OBD_MMC_ERROR, "Can't connect or mount MMC/SD");
 		UNLOCK_SD_SPI;
-		return;
+		return nullptr;
 	}
 
-	#if HAL_USE_USB_MSD
-		BaseBlockDevice *bbdp = (BaseBlockDevice*)&MMCD1;
-		msdStart(&USBMSD1, usb_driver, bbdp, blkbuf, &scsi_inquiry_response, NULL);
-	#endif
-
 	UNLOCK_SD_SPI;
+	return (BaseBlockDevice*)&MMCD1;
+}
+
+// Initialize and mount the SD card.
+// Returns true if the filesystem was successfully mounted for writing.
+static bool mountMmc() {
+	auto cardBlockDevice = initializeMmcBlockDevice();
+
 #if HAL_USE_USB_MSD
-	sdStatus = SD_STATE_MOUNTED;
-	return;
+	msdObjectInit(&USBMSD1);
+	
+	if (cardBlockDevice) {
+		// Mount the real card to USB
+		msdStart(&USBMSD1, usb_driver, cardBlockDevice, blkbuf, &scsi_inquiry_response, NULL);
+	} else {
+		// Mount a  "no media" device to USB
+		msdMountNullDevice(&USBMSD1, usb_driver, blkbuf, &scsi_inquiry_response);
+	}
+
+	// TODO: local mount and log if USB not connected
+	return false;
 #endif
 
+	// if no card, don't try to mount FS
+	if (!cardBlockDevice) {
+		return false;
+	}
+
 	// if Ok - mount FS now
 	memset(&MMC_FS, 0, sizeof(FATFS));
 	if (f_mount(&MMC_FS, "/", 1) == FR_OK) {
@@ -410,12 +424,16 @@ static void MMCmount(void) {
 		createLogFile();
 		fileCreatedCounter++;
 		scheduleMsg(&logger, "MMC/SD mounted!");
+		return true;
 	} else {
 		sdStatus = SD_STATE_MOUNT_FAILED;
+		return false;
 	}
 }
 
-class SdLogBufferWriter final : public BufferedWriter<512> {
+struct SdLogBufferWriter final : public BufferedWriter<512> {
+	bool failed = false;
+
 	size_t writeInternal(const char* buffer, size_t count) override {
 		size_t bytesWritten;
 
@@ -426,7 +444,12 @@ class SdLogBufferWriter final : public BufferedWriter<512> {
 
 		if (bytesWritten != count) {
 			printError("write error or disk full", err); // error or disk full
+
+			// Close file and unmount volume
 			mmcUnMount();
+			UNLOCK_SD_SPI;
+			failed = true;
+			return 0;
 		} else {
 			writeCounter++;
 			totalWritesCounter++;
@@ -465,20 +488,11 @@ static THD_FUNCTION(MMCmonThread, arg) {
 			tsOutputChannels.debugIntField4 = fileCreatedCounter;
 		}
 
-		// this returns TRUE if SD module is there, even without an SD card?
-		if (blkIsInserted(&MMCD1)) {
+		writeLogLine(logBuffer);
 
-			if (!isSdCardAlive()) {
-				MMCmount();
-			}
-		} else {
-			sdStatus = SD_STATE_NOT_INSERTED;
-		}
-
-		if (isSdCardAlive()) {
-			writeLogLine(logBuffer);
-		} else {
-			chThdSleepMilliseconds(100);
+		// Something went wrong (already handled), so cancel further writes
+		if (logBuffer.failed) {
+			return;
 		}
 
 		auto period = CONFIG(sdCardPeriodMs);
@@ -494,32 +508,15 @@ bool isSdCardAlive(void) {
 
 void initMmcCard(void) {
 	logName[0] = 0;
-	addConsoleAction("sdinfo", sdStatistics);
-	if (!CONFIG(isSdCardEnabled)) {
+
+	if (!mountMmc()) {
+		// no card present, don't start thread
 		return;
 	}
 
-	mmcSpiDevice = CONFIG(sdCardSpiDevice);
-
-	efiAssertVoid(OBD_PCM_Processor_Fault, mmcSpiDevice != SPI_NONE, "SD card enabled, but no SPI device configured!");
-
-	// todo: reuse initSpiCs method?
-	hs_spicfg.ssport = ls_spicfg.ssport = getHwPort("mmc", CONFIG(sdCardCsPin));
-	hs_spicfg.sspad = ls_spicfg.sspad = getHwPin("mmc", CONFIG(sdCardCsPin));
-	mmccfg.spip = getSpiDevice(mmcSpiDevice);
-
-	/**
-	 * FYI: SPI does not work with CCM memory, be sure to have main() stack in RAM, not in CCMRAM
-	 */
-
-	// start to initialize MMC/SD
-	mmcObjectInit(&MMCD1); 						// Initializes an instance.
-	mmcStart(&MMCD1, &mmccfg);
-
 	chThdCreateStatic(mmcThreadStack, sizeof(mmcThreadStack), LOWPRIO, (tfunc_t)(void*) MMCmonThread, NULL);
 
-	addConsoleAction("mountsd", MMCmount);
-	addConsoleAction("umountsd", mmcUnMount);
+	addConsoleAction("sdinfo", sdStatistics);
 	addConsoleActionS("ls", listDirectory);
 	addConsoleActionS("del", removeFile);
 	addConsoleAction("incfilename", incLogFileName);