diff --git a/src/machine/machine_stm32_flash.go b/src/machine/machine_stm32_flash.go
index 00ec718c..898c50dc 100644
--- a/src/machine/machine_stm32_flash.go
+++ b/src/machine/machine_stm32_flash.go
@@ -73,11 +73,15 @@ func (f flashBlockDevice) EraseBlockSize() int64 {
 // transparently coalesce ranges of blocks into larger bundles if the chip
 // supports this. The start and len parameters are in block numbers, use
 // EraseBlockSize to map addresses to blocks.
+// Note that block 0 should map to the address of FlashDataStart().
 func (f flashBlockDevice) EraseBlocks(start, len int64) error {
+	var address uintptr = uintptr(start*f.EraseBlockSize()) + FlashDataStart()
+	blk := int64(address-uintptr(memoryStart)) / f.EraseBlockSize()
+
 	unlockFlash()
 	defer lockFlash()
 
-	for i := start; i < start+len; i++ {
+	for i := blk; i < blk+len; i++ {
 		if err := eraseBlock(uint32(i)); err != nil {
 			return err
 		}
diff --git a/src/machine/machine_stm32f4.go b/src/machine/machine_stm32f4.go
index 016c1019..3b8923cb 100644
--- a/src/machine/machine_stm32f4.go
+++ b/src/machine/machine_stm32f4.go
@@ -891,7 +891,7 @@ func writeFlashData(address uintptr, data []byte) (int, error) {
 		// start write operation
 		stm32.FLASH.SetCR_PG(1)
 
-		*(*uint16)(unsafe.Pointer(address)) = binary.BigEndian.Uint16(data[i : i+writeBlockSize])
+		*(*uint16)(unsafe.Pointer(address)) = binary.LittleEndian.Uint16(data[i : i+writeBlockSize])
 
 		waitUntilFlashDone()
 
diff --git a/src/machine/machine_stm32l4.go b/src/machine/machine_stm32l4.go
index 2ac00200..f60a77e7 100644
--- a/src/machine/machine_stm32l4.go
+++ b/src/machine/machine_stm32l4.go
@@ -595,13 +595,13 @@ func writeFlashData(address uintptr, data []byte) (int, error) {
 		// start page write operation
 		stm32.FLASH.SetCR_PG(1)
 
-		// write first word using double-word low order word
-		*(*uint32)(unsafe.Pointer(address)) = binary.BigEndian.Uint32(data[j+writeBlockSize/2 : j+writeBlockSize])
+		// write second word using double-word high order word
+		*(*uint32)(unsafe.Pointer(address)) = binary.LittleEndian.Uint32(data[j : j+writeBlockSize/2])
 
 		address += writeBlockSize / 2
 
-		// write second word using double-word high order word
-		*(*uint32)(unsafe.Pointer(address)) = binary.BigEndian.Uint32(data[j : j+writeBlockSize/2])
+		// write first word using double-word low order word
+		*(*uint32)(unsafe.Pointer(address)) = binary.LittleEndian.Uint32(data[j+writeBlockSize/2 : j+writeBlockSize])
 
 		waitUntilFlashDone()
 
diff --git a/src/machine/machine_stm32wlx.go b/src/machine/machine_stm32wlx.go
index 7971d7a3..010d038e 100644
--- a/src/machine/machine_stm32wlx.go
+++ b/src/machine/machine_stm32wlx.go
@@ -484,13 +484,13 @@ func writeFlashData(address uintptr, data []byte) (int, error) {
 		// start page write operation
 		stm32.FLASH.SetCR_PG(1)
 
-		// write first word using double-word low order word
-		*(*uint32)(unsafe.Pointer(address)) = binary.BigEndian.Uint32(data[j+writeBlockSize/2 : j+writeBlockSize])
+		// write first word using double-word high order word
+		*(*uint32)(unsafe.Pointer(address)) = binary.LittleEndian.Uint32(data[j : j+writeBlockSize/2])
 
 		address += writeBlockSize / 2
 
-		// write second word using double-word high order word
-		*(*uint32)(unsafe.Pointer(address)) = binary.BigEndian.Uint32(data[j : j+writeBlockSize/2])
+		// write second word using double-word low order word
+		*(*uint32)(unsafe.Pointer(address)) = binary.LittleEndian.Uint32(data[j+writeBlockSize/2 : j+writeBlockSize])
 
 		waitUntilFlashDone()