Unable to upload programs to an Arduino Mega2560 (!!! Bug)


I am newbie to Arduino… I bought a Mega2560 and a Duemilanove before. Then I tried to make a batteries tester with Arduino. But sometimes I can not upload to Mega2560, but Duemilanove can, with same sketch!!! It will halt up when uploading to Mega2560. I have to un-plug the USB cable and plug again. The 8u2 version is 0001 already.
Following is part of sketch, it has upload problem if I don’t comment out the red section…

Does anyone can give some tips?


void loop() {
switch(mode) {
//read button press
if(readPress) {
readPress = 0;
Serial.println(“Read back…”);
// if(testCount == 0) {
// Serial.println(“No record found!!!”);
// }
for(int i = 0; i < testCount; i++) {
Serial.print(" “);
for(int j = 0; j < numberOfBattery; j++) {
Serial.print(result[i * numberOfBattery + j]);
Serial.print(” V ");
} //for
} //for
isRead = 0;
} //if
//Start button means start testing…
if((startPress == 1) && (isRead == 0)) {
mode = TESTING;
startPress = 0;
sec10 = 0;
seconds = 0;
} else {
startPress = 0;

The three exclamation marks in a row are the problem. The 2560 bootloader incorrectly interprets them as a command to enter "monitor mode".

Thank you for your reply.
But the “three exclamation marks” are added on this forum only for easy reading, not in IDE. In IDE, I just use “//” to comment out. And the problem is it will fail to upload to 2560 if I take out the “//” likes following. It is not my first time, I tried before then I am making a new code, but still happened.

Best regards,

 Serial.println("Read back.............");

          if(testCount == 0) {
           Serial.println("No record found!!!!"); 

          for(int i = 0; i < testCount; i++) {

Serial.println(“No record found!!!”); // <— These exclamation marks are the problem.


Thank you! I will try it! (update) I tried it and it works!, Thanks a lot.

Best regards, ANewbie

Thank you for the follow-up. I’m glad you have it working.

Just so you know, with your Duemilanove you could replace the bootloader on your Mega2560 with a version that does not have this bug.

Thank you for your information. However, I think I will not touch bootloader at this moment. And I will keep in mind about the bug.