Ficara Emilio Pietro Giovanni ~ TTL to RS232 interface 3 Volts powered
This circuit converts TTL logic levels to EIA-RS232 levels and is 3V powered. The IC used may be MAX3232 or ST3232 or similar from other sources. Such ICs are suited for operating voltage of 3 Volts. I connected my PC to a China clone tablet using this interface and the NET/USB expansion board of the tablet (shown in the picture). Please, note that the RX and TX wires must be crossed in this application !
The printed circuit drawings in 1:1 scale PDF can be downloaded here
The circuit schematics PDF can be downloaded here