Video of flashing a GBA repro
As of this point in time the cart reader supports 3 types of GBA repro pcbs:
Intel 4000L0YBQ0 (32MB)
Macronix MX29GL128E (16MB)
Fujitsu MSP55LV128 (16MB)
Please set the jumpers up like this and use a good USB port or mobile phone charger with 1A:
I recommend buying a repro that already has a battery installed as they all come with a standard cmos sram save chip that needs a standby voltage to keep the save data.
Upon further inspection of the repros that come without a battery it becomes apparent that the save is located inside the rom area. When booting the game there is a routine hacked into the rom that copies the save from the flashrom into the sram. When you save in-game the save gets copied back into the flashrom.
You can extract this hacked-in save game by dumping the rom and then opening it with the Visual Boy Advance emulator. Once started the game will copy the save into sram and VBA will then create a sav file.
Now you can use this sav file together with the unhacked retail version of the rom which will recognize the save and attempts to repair it, which should succeed.
This also means that roms that are not hacked in the same way will lose their save game if you don't add a battery yourself.
Remember that you will have to patch all roms with eeprom/flashrom save type to sram save using a program like GBA TOOL ADVANCE.
One last interesting detail is that on the MX29GL128E and MSP55LV128 pcb the D0 and D1 pins of the flashrom have been switched around so that the flashrom needs slightly modified flash commands.