So, to open up a serial port and successfully transmit data from the balance through the serial port, i need to make sure that the settings on the serialPort object match the actual settings of the balance.
Now, the question is how do i detect that the connection hasn’t been established due to the settings being different? No exception is thrown by serialPort.Open to indicate that the connection has been established. Yes, the settings are valid, but if they don’t match the device (balance) settings; I am in the dark as to why the weight off the balance is not being captured.
Any input here?
If things are close, but still incorrect, the .NET serial port object may not even give you an error (that is, until something catastrophic occurs).
My most common serial port communication failure occurs due to mismatched baud rates. If you have a message that you know you can get an ‘echo’ for, try that as part of a handshaking effort. Perhaps the device you’re connecting to has a ‘status’ message. No harm will come from requesting it, and you will find out if communication is flowing correctly.
For software handshaking (xon xoff) There’s very little you can do to detect whether or not it’s configured right. The serial port object can do anything from ignore it completely to have thread exception errors, depending on the underlying serial port driver implementation. I’ve had serial port drivers that completely ignore xon/xoff, and pass the characters straight into the program – yikes!
For hardware handshaking, the basic echo strategy for baud rate may work, depending on how your device works. If you know that it will do hardware handshaking, you may be able to detect it and turn it on. If the device requires hardware handshaking and it’s not on, you may get nothing, and vice versa.
Another setting that’s more rarely used is the DTR pin – data terminal ready. Some serial devices require that this be asserted (ie, set to true) to indicate that it’s time to start sending data. It’s set to false by default; give toggling it a whirl.
Note that the serial port object is … finicky. While not necessarily required, I would consider closing the port before you make any changes.
Edit:
Thanks to your comments, it looks like this is your device. It says the default settings should be:
It doesn’t specify how many data bits, but the device says it supports 7 and 8. I’d try both of those. It also says it supports 600, 1200, 2400, 4800, 9600, and 19200 baud.
If you’ve turned on hardware handshaking, enabled DTR (different things) and cycled through all the different baud rates, there’s a good chance that it’s not your settings. It could be that the serial cable that’s being used may be wired incorrectly for your device. Some serial cables are ‘passthrough’ cables, where the 1-9 pins on one side match exactly with the 1-9 pins on the other. Then, you have ‘crossover’ cables, where the ‘TX’ and ‘RX’ cables are switched (so that when one side transmits, the other side receives, a very handy cable.)
Consider looking at the command table in the back of the manual there; there’s a ‘print software version’ command you could issue to get some type of echo back.