Issues uploading to MEGA 2560 based RAMBo board

I am getting the infamous

" avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer"

error when I try to upload some new Repetier firmware to the board for my 3D printer. The board came pre-loaded with some older firmware and it runs perfectly fine aside from the fact that the motors move the in the wrong direction which is why I need to upload edited firmware with the motor direction changed.

I am running Mac OS X 10.8.3 and here is everything I have tried...

Tried uploading from a different computer running OS X 10.6.8

Tried uploading other sketches including blink, no go

Tried older IDE versions

Tried different USB cables with both computers

Serial port is right

Board selection is MEGA 2560

I removed all the triple !!! in the code

Pressed the reset button after compiling

Tried with the USB as a power source as well as the 12V DC I have wired to the board

Tried different USB ports on my computer

Unplugged and re-plugged everything

I have an LCD controller attached and here are the exact things that happen when I try to upload.

Everything complies fine and the board auto-resets before the upload begins, the TX LED flashes a lot and the RX LED flashes about 4 or 5 times then I get the timeout error and the TX LED stays lit.

I have never used an Arduino before and know nothing about it except for what I have gleaned from reading thousands of forum posts in the past two days. Hopefully someone can help me find the answer and we can put this one to bed once and for all.

Hi,

I had the same problem and I may have the solution.

In my source I used a character sequence as this " !!! " inside a warning message.
I have removed the code line and as a miracle all was working again.
I tried then to put the line back in my code and I was just unable to send it back to the board.

It seems that the board interprets some sequences as a command or so instead of just code.

Check if your source contains that sequence "!!!" remove our replace it by "!" and try....

In my case this was the problem !

You are uploading from the IDE?
The chip has a bootloader on it?
If not, either install one so you can do serial downloads, or upload with an AVR Programmer using the ICSP header.
If it does have one, press & hold the reset button, release it when the IDE shows "compiled xxx of 256K bytes" or similar.
Might have to try a few times to get the timing right. Helps to check Verbose output under File:Preferences.