Note: the picture in this log entry shows a fully modified board.

Prepare the board:

1. remove LED "IN"
2. remove LED "OUT"
3. interrupt the connection between LM2596 pin 5 (!ON/OFF) and GND (i.e. cut the pin in the middle, and de-solder the lower half)
4. carefully cut the copper trace between the LM2596 heat sink GND and the 330R next to the trimmer.
5. cut the copper trace between LM317 pin2 and anode pad of LED "IN". Expose some of the copper of the trace near said pad.

Add new components:

1. solder a C 100nF between LM317 pin 2 and GND on the backside of the PCB
2. solder a 10µF ceramics capacitor 0603 or 0805 over the now cut copper trace between the LM2596 heat sink GND and the adjacent pad of the 330R next to the trimmer
3. solder a 47R 0805 resistor to the pads of LED "IN"
4. solder a 1k8 0805 resistor to the pads of LED "OUT"

Make new connections for controlling the LM2596:

1. add a wire between the cathode pad of LED "OUT" (PB4) and LM2596 pin 5
2. add a wire between the copper trace near the anode pad of LED "IN" (PC3) to the 330R pad, where also the 10µF capacitor is connected
3. connect (pin 2 || pin 3) of the trimmer to pin 1 of the voltage adjust trimmer on the board

Make the µC accessible:

1. add a 2 pin programming connector to GND and pin 4 of the 7S-LED display (segment C, PD1/SWIM).
2. solder the anode of a 1N4148 diode to pin 3 of the 7S-LED display (segment DP, PC7). Wire a 3 pin connector to the anode and the cathode of the diode and to GND.

Program the µC:

1. get the binary from the [v2.2.8 release](https://github.com/TG9541/stm8ef/releases/tag/v2.2.8) (or later)
2. programming the STM8S003F3P6 with an ST-LINK adapter by programming SWIM and GND to the programming connector

Test the serial connection:

1. connect the RxD line of a serial-TTL converter to the "anode pin" of the serial connector, and TxD to the "cathode pin"
2. start a terminal program at 9600 baud, and test the connection by pressing ENTER

Note: the serial interface works in "half-duplex" mode without collision detection. This is sufficient for interactive use, and for command-response automation.