I am experimenting with my PC's RS-232 interface on Win7. I want to toggle the RTS line state with "mode com1: rts=on" command. However monitoring the RTS line with multimeter shows that the state of the line is momentarily pulsed to on-state. I wonder what is going on?
1
-
1Yes; A pulse would be excepted. The pulse does toggle the state.– RamhoundJan 14, 2015 at 18:55
Add a comment
|
1 Answer
To be able to precisely turn on or off (i.e. voltage or no voltage) certain pins in io-ports of a computer you need to gain exclusive access to the software interface to make sure the OS doesn't either STOP you, or start fiddling with it in the midst of your operations.
You also somehow have to make sure the/any driver software doesn't step into it in the same style.
THEN you may alter the hardware circuitry settings to get it to do what you wish. Note that some things still might be impossible due to limitations in the design of the hardware.
I doubt that the dos prompt mode program can actually set and KEEP the rts output on or off. You better check what mode /? prints about it, even googling on it might help to inform yourself.
RTS is short for Request To Send which is used in hardware type handshaking for serial (RS232) communication. This is to be interconnected with "CTS" (Clear to Send) at the other end, assuming you have a similar device there (DCE to DCE communication).
See http://en.wikipedia.org/wiki/RS-232 for more details.
