diff --git a/drv/dma_mbuf.c b/drv/dma_mbuf.c
index dd7a3cc..8d10b27 100644
--- a/drv/dma_mbuf.c
+++ b/drv/dma_mbuf.c
@@ -18,8 +18,11 @@
 
 static void mbuf_callback(enum DmaIRQSource src, volatile void* param);
 
-#define byte_index (((uint8_t**)buffer->buffers)[buffer->buffer_index][buffer->buffer_size + 1])
-#define dma_byte_index (((uint8_t**)buffer->buffers)[buffer->dma_buffer_index][buffer->buffer_size + 1])
+//take last 2 bytes of a buffer and assemble them store the current byte index
+#define byte_index (((uint16_t**)buffer->buffers) \
+		[buffer->buffer_index][buffer->buffer_size/2])
+#define dma_byte_index (((uint16_t**)buffer->buffers) \
+		[buffer->dma_buffer_index][buffer->buffer_size/2])
 
 
 //--local variables-------------------------------------------------------------
diff --git a/drv/dma_mbuf.h b/drv/dma_mbuf.h
index f26a6d4..4ab6952 100644
--- a/drv/dma_mbuf.h
+++ b/drv/dma_mbuf.h
@@ -43,7 +43,8 @@ struct DmaMultiBuffer {
  * Configure a DMA multibuffer for a single DMA channel. A list of buffers is
  * used to allow concurent write and DMA tranfers to the specified destination
  * wich must be a peripheral. The DMA's priority is also given as parameters.
- * The peripheral's specific configuration must be handled separately.
+ * The peripheral's specific configuration must be handled separately. 2 bytes
+ * are reserved in each buffer for index storage.
  *
  * This system needs to be started manually: dma_mbuf_refresh() should be called
  * whenever a DMA transfer can be started. This can be done manually after