We are trying to make our own board for Scratch which can be interfaced through the serial port.
The only schematic we have been able to find out for the serial interfacing of ScratchBoard is here:
The PIC microcontroller which has been used implements TTL (transistor-transistor logic) as far as we know. While the RS-232 implements a different logic. As far as we understand, there must be a module - an IC - between the RS-232 serial port and PIC16F676 which should translate the TTL from the microcontoller's output into the logic understood by RS-232 before feeding it to the serial port in order to make this work.
Please guide us. Regards,