diff --git a/js/stm32.js b/js/stm32.js
index 9e770f5598..c66197b850 100644
--- a/js/stm32.js
+++ b/js/stm32.js
@@ -40,6 +40,10 @@ var STM32_protocol = function() {
     };
     
     // Erase (x043) and Extended Erase (0x44) are exclusive. A device may support either the Erase command or the Extended Erase command but not both.
+    
+    // debug variables
+    this.serial_bytes_send;
+    this.serial_bytes_received;
 };
 
 // string = string .. duh
@@ -144,6 +148,9 @@ STM32_protocol.prototype.initialize = function() {
 
     self.verify_hex = [];
     
+    self.serial_bytes_send = 0;
+    self.serial_bytes_received = 0;
+    
     self.upload_time_start = microtime();
     
     self.steps_executed = 0;
@@ -189,6 +196,8 @@ STM32_protocol.prototype.read = function() {
             for (var i = 0; i < data.length; i++) {
                 self.receive_buffer.push(data[i]);  
             }
+            
+            self.serial_bytes_received += data.length;
         }
     });
     
@@ -207,6 +216,8 @@ STM32_protocol.prototype.read = function() {
 // bytes_to_read = received bytes necessary to trigger read_callback
 // callback = function that will be executed after received bytes = bytes_to_read
 STM32_protocol.prototype.send = function(Array, bytes_to_read, callback) {
+    var self = this;
+    
     var bufferOut = new ArrayBuffer(Array.length);
     var bufferView = new Uint8Array(bufferOut);
     
@@ -218,7 +229,11 @@ STM32_protocol.prototype.send = function(Array, bytes_to_read, callback) {
     this.read_callback = callback; 
 
     // send over the actual data
-    chrome.serial.write(connectionId, bufferOut, function(writeInfo) {}); 
+    chrome.serial.write(connectionId, bufferOut, function(writeInfo) {
+        if (writeInfo.bytesWritten > 0) {
+            self.serial_bytes_send += writeInfo.bytesWritten;
+        }
+    }); 
 };
 
 // val = single byte to be verified 
@@ -564,8 +579,8 @@ STM32_protocol.prototype.upload_procedure = function(step) {
             GUI.interval_remove('firmware_uploader_read'); // stop reading serial
             GUI.interval_remove('STM32_timeout'); // stop STM32 timeout timer (everything is finished now)
             
-            console.log('Script finished after: ' + (microtime() - self.upload_time_start).toFixed(4) + ' seconds');
-            console.log('Script finished after: ' + self.steps_executed + ' steps');
+            console.log('Transfered: ' + self.serial_bytes_send + ' bytes, Received: ' + self.serial_bytes_received + ' bytes');
+            console.log('Script finished after: ' + (microtime() - self.upload_time_start).toFixed(4) + ' seconds, ' + self.steps_executed + ' steps');
             
             // close connection
             chrome.serial.close(connectionId, function(result) {