Portable Pro Mini programmer using serial TX/RX

Hi everybody. I'm looking for your help regarding Serial programming. Usually I have the classical chain for Pro Mini programming : computer - USB2.0 to TTL converter - Pins GND, VCC, TX, RX and DTR on the Pro Mini.

As I'd like to reprogram Pro Minis, I'm looking forward to creating a box with an SPI EEPROM containing the .hex file to be uploaded and a Pro Mini to emulate the computer - TTL converter part.

I'm quite sure that somebody else has already thought about it but I'm unable to find something on this forum (not sur I'm searching the right thing...).

Do anybody has an idea or a link with some information ? Thanks for your help.

Way ahead of you sport. http://www.crossroadsfencing.com/BobuinoRev17/

With maybe a programming cable adapter if you didn't break out the ICSP pins http://www.hobbyking.com/hobbyking/store/__46316__Atmel_Atmega_Socket_Firmware_Flashing_Tool_US_Warehouse_.html?strSearch=atmega

Thank you for your quick reply. I had previously found your board and also had a look at Nick Gammon code (which is very well documented). But the Pro Minis I want to upgrade are in an enclosure with only the common UART interface pins accessible (as stated, today I do the upgrades with a computer connected with a USB TTL cable to the RX/TX pins)…

If I’m right your board and the associated software uses the SPI and the programming cable needs an access to the chip itself… Please feel free to correct me if I’m wrong.

That’s why I’m looking for something using RX/TX pins…

You're correct, it is set up for ICSP programming, not Rx/Tx/DTR for reset.

I will check with the code creater, Nick Gammon, and see about using the Serial pins on the programmer to be able to do serial programing. Maybe add a couple jumpers for Rx/Tx, bring the pins out on the ICSP header with a 3rd being used for software controllable reset signal, and use a 2x3 to 1x6 programming cable.

If you select File:Preferences and turn on Verbose Outputs, you can see all interfacing that has to be mimicked once the “Compiled xxx of 32xxx bytes” message is posted.

Thanks for your advise. Looking at the verbose and having a glance at the bootloader source code I think I'll be able to manage a solution. I'm not sure the solution will be available for any Atmel device but will work great with Pro Mini board...

Will give info according to the progress.