Bootloader without the Reset/DTR function

Other Hardware 3rd Party Boards
1

Hi All,

I need some help with the following issue:

  1. I am using an existing software on Windows XP, which communicates with my Arduino Duemilanove (I can't use the Uno)

  2. This software (I can't modify it) resets my Arduino board when it tries to communicate with it via the DTR line so my system doesn't work

  3. If I unsold C13 (DTR line), it's working well but I can't download new firmwares

So I am wondering if there is a solution?

Maybe to use a board without C13 and include in the Arduino software a command (sent by the PC) to reset the board and go directly to teh bootloader section. Then use AVRdude to download the new firmware?
Any help on how to start?

Thx!!!

2

My understanding is that with the auto reset function removed, you can still upload new software if you press the reset button at just the right time.

Alternatively, solder a 2-pin header in place of C13 so that you can easily reinstate it when you need to upload new firmware.

Alternatively, leave C13 in place and disable the auto-reset by connecting a 110 to 124 ohm resistor between the Reset and +5v pins. Remove this to upload new software.

3

Thanks for the reply and for the tips.
Unfortunatly, as I should have mentionned before, my Arduino board is not accessible in this application (in an closed enclosure).
It's why I am looking for a solution with the bootloader started by the Host application via software. But, right now, I am not sure how to start this...

4

Assuming the 120 ohm resistor to disable auto reset works for your board, you could try using a PNP transistor with emitter to +5v, collector to Reset via a 120 ohm resistor, base to an Arduino pin through a 1K resistor. When you configure the Arduino pin as an output and drive it low, it should disable the auto reset. If it doesn't, then if you connect a 1K resistor in series with C13 I think it should work then.

5

Thank you DC42.

I have just tried your idea and it's working great! Now I don't have any board reset issues when the HOST opens the port COM. I can control the DTR/Reste function by software.

I used a P channel MOSFET BSS84 with a 200 Ohm resistor (120 Ohm doesn't work) connected betwen +5v and Reset. The gate of the MOSFET is controlled by a pin of the AVR.