10pcs Mini RS232 to TTL MAX3232 to TTL Level Converter Board Serial Converter Board RS232 to TTL Serial

Very small and neat, do exactly what they're meant to do. Interfaced my PV/Battery/Inverter unit with ESP32 perfectly.

Pros: Cheap, kinda worksCons: Pads break off the board very easily, the RS232 output isn't really to spec, but it's good enough that most devices will accept it.Take note of the writing "RS232<->TTL" on the board. This tells you which pads are for which interfaceTo hook up to an Arduino like device...Serial2.begin(9600, SERIAL_8N1, myRxPin, myTxPin);Converter -> Microcontroller:" + " connects to "3V3" or "5V"" - " to "GND"TTL "<-" (pointing toward board centre) to TX pinTTL "->" (pointing toward board edge) to RX pixConverter -> RS232 deviceRS232 "->" (toward board centre) to RS232 RX (D-sub pin 2)RS232 "<-" (toward board edge) to RS232 TX (D-sub pin 3)The top and bottom arrow pads are separate on either side of the board. You can hook up RTS/CTS signals on the other side.Do not connect any of the + or - pads to the RS232 side. The 4 pads for each are fully connected.