HELP! Cant get 2560 programming through a 16U2

Using Arduino Microcontrollers
1

Hey Guys,

Can anybody offer any help on this:
I can only program an ATmega2560 once through a 16U2 and after that, I need to re-burn the 2560 bootloader to program it again :frowning: This wipes the EEPROM every time and also requires the use of an AVR ISP (I'm using the MKii)...

It's a stand alone PCB board. I'm using the same bootloaders, lock bits and fuse bits as an Arduino Mega2560 board which of course works perfectly every time!

Has anybody got ANY suggestions as to what the problem might be or anything that I can try to resolve it?

Thanks so much, ANY suggestions would be great!
Rob

2

Is the reset circuit working correctly? The 16u2 should reset the chip when you open a serial connection. Is it doing that? If not, that will produce the behavior you have observed.
Post your schematic.

3

Thanks for the feedback DrAzzy, and I am eternally grateful!!!

I checkout what was happening on the reset and of course it was not following the same pattern as the Arduino board (which is shown in the picture attached).

I had the 16U2 connected to the controller reset correctly, however, we have a second controller which is used for MIDI TTL to USB conversion and I also had it connected to the reset. Of course it was not allowing the controller reset to pull down to ground. So I removed the capacitor.

I'm a very happy person right now!!!!!

Thanks again for the help DrAzzy,
Today, you are a hero :slight_smile:

FullSizeRender.jpg