On most computer, the address for the COMM1 serial port is 3F8 hex or 1016 decimal. I believe the syntax to use the OUT command in QBasic is OUT (Address), (1 Byte Data) Try using...
OUT 3F8h, 85 should send a 01010101 (toggle bit) out your RS232 port.
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Connect pin 2 and 3 on your COMM port (your making a loop-back plug) to verify to comm port is working. You cannot accuratly measure the voltage levels of you comm port with a digital multimeter. |