text: > Confirming transmission using hardware and software serial on the same board
  Topic: Confirming transmission using hardware and software serial on the same board (Read 1 time) previous topic - next topic
  I've been working on controlling a pH meter across RS-232 and I've tried many different things to get the set up to work, but nothing has succeeded. I'm at the point where I just want to confirm that my softwareserial port is actually able to send and receive data as I've been able to confirm that the pH meter behaves as expected.
  I am using a Leonardo board and I want the hardware serial to connect to the pc so I can record data, so the softwareserial will communicate with the pH meter. To make sure the softwareserial connection is working, I've been trying to make a simple loop where the hardware serial sends a short string to the RX pin of the software serial. When there are characters available an LED should light up.
  I haven't been able to get pHmeter to show any signs that it's sending or receiving input. pHmeter.available() is always zero. Writing from pHmeter never produces characters in the hardwareserial buffer either.
  // ;//wait for Leo to connect
  Re: Confirming transmission using hardware and software serial on the same board
  Mar 28, 2013, 02:36 am
  I believe however that this is not going to give you more information, and that the problem is at the physical level. From your description it seems that the pH meter communicates at RS-232 signal levels, which cannot (and *must* not) be fed directly to an Arduino pin. The voltage can reach 25V and also be negative, and would certainly damage the arduino. If this is your case you should use a level converter. Please provide more information on the pH meter and on how it is connected (including TX, RX, VCC, GND).