Solved My Own Problem: Program Arduino Pro Mini Using Serial + MAX232 Board

Good Day. I hope this helps anyone else who has the right (wrong) type of RS-232 to TTL converter with a MAX232 or similar IC and who is tired of having to hit the reset button on the Pro Mini at just the right moment to program it. I have several low cost RS-232 to TTL converters that only support the RX and TX lines. DTR was not wired on the PCB. A picture of the TTL converter board is attached to help you see if you have the same board.

Following the schematic at I wired the D-Sub pin 4 to pin 6 and to the MAX3232 pin 8. Before accusing me of a typo it really is a MAX3232 but the pinout is the same where it matters. As a “quick and dirty” connection pin for the newly available DTR line I added a header pin directly to the MAX3232 pin 9.

Top side and bottom side wiring and connections are shown in the other attached pictures. Power was provided to the MAX3232 board through a USB-barrel connector cable that came with it. I used the VCC pin from the MAX3232 board to provide power to the RAW input on the Pro Mini board.

Best Wishes,