I purchased a RS232 shifter board a couple of weeks before from Sparkfun and can't resolve the problem.
A. I have been trying to receive GPS RS232 signalsfrom a DB9 output from a computer to an Arduino. I tried a RS232 to TTL converter plug. I couldn't get it to work.
B. So I bought your RS232 shifter board. I liked it a lot because we have Green LED to monitor TX signals and Red to monitor RX signal.
I can get RS232 signals between computers all day long. The I chatted with Sparfun and he said tie the TTL RX and TX lines together and gave me a way to send text typed into the serial program and have that program receive what I typed and also seeing the red and green LEDs flashing showing that the board is working(loop test). It worked fine.
Your schematic doesn't show where the LEDs are( I assume that they are on the RS232 side)
I still can't get TTL flow.
My question is:
I'm only needing to receive data and when I get it connected I get the TX (green LED) to flash. If I shift the lead to other lead DB9 pin 2 to pin3, I would expect the Red LED to light because the voltage is shifted to the other line, but I can't get the red LED to flash no matter what. No matter what I do, I can't get the red LED to flash. I measured voltages from the RX pin on the input to ground and get around 5v to 13 volts.
I know that I am doing something wrong, but can't figure what it is.
Any ideas?
Fred