Serial Programming

Hello everyone, I am working on a project with aim is to detect +5V signal from an external device and an application running on PC detects it and increments a variable value each time it receives this signal. Well for this I am using RS232/USB adaptor and passing this +5V signal to RXD pin of RS232 but unable to get any data checking with software Advanced Serial Port Monitor. please help me to know why is it happening and what type of data is generated while passing 5V signal to RS232 RxD pin.

Well for this I am using RS232/USB adaptor and passing this +5V signal to RXD pin of RS232 but unable to get any data

I don't think this is going to work, because RS-232 uses negative voltage to represent logic one on data transmission lines. You'd need to toggle RxD from -5V to +5V (or better ±10 ~ ±12 V) and the signal must follow the protocol, i.e. start bit, data bits, [optional] stop bit at the speed to which the receiver is configured.

If you have Netduino board, connect the input signal to any of its digital pins, create an instance of InterruptPort configured to detect event that you are interested in (low and/or high edge) and notify the PC via serial communication link from the interrupt event handler. You'd need USB <-> TTL serial converter, unless you have Netduino Mini - Netduino and Netduino Plus do not have RS-232 voltage level shifter, Mini does.

If you don't have any .NET Micro Framework device, you might try to connect the input signal to RS-232 control lines, such as DTR or RTS and see in your diagnostic program whether the change is detected or not. Or, you could use a parallel port, if your computer has it.