Since you're not using handshaking, your task is much easier. In other words, cross over your pins 2 and 3 and retry :-) here's a good reference Therefore you need a "null modem" cable to communicate between two com ports on two DTE machines (ie, typical PCs). the difference between DTE (data terminal emulator) and DCE (data communication equipment) is that the TX and RX pins are swapped (pins 2 and 3, on a DB-9) in order to communicate straight through, one has to be a DTE and one a DCE. I hope this is correct?Ĭonnecting one serial cable to the other, and running two instances of HyperTerminal on the two different ports will verify whether or not it works correctly.īut the thing to remember is both of your com ports are acting as a DTE. Therefore I have always set the Handshake option to "none". So I guess there's a difference between the voltage levels of the two ports so maybe you're right and the USB-to-Serial bridge is not designed to meet the real RS232 standards.Ĭoncerning the handshake signals: The two cables I am using have only 3 signal lines (RX, TX and GND I guess) populated through a headphone jack. Using two HyperTerminal programs, I tried to type into one of them and look if the text appears in the other. The next test was to connect COM1 to COM5, so I created a small adapter cable where RX of COM1 connects to TX of COM5 and vice-versa. So this is working correctly, at least it is able to understand it's own signals -) To test if COM5 can talk to itself, I shorted the TX and RX signals and there it is: the echo in the HyperTerminal program.
If I connect my device to COM1, it works correctly, with COM5, no answer is recieved. The protocol I am using is really simple, I write the string "mem" to the port and receive the answer.
PROLIFIC USB TO SERIAL DRIVER COULD NOT START WINDOWS
I used the Windows HyperTerminal program to test both COM ports. If it does work, and your program truly is apples-for-apples, then I would work on tracing down the problem i described above in (1). Make sure that your converter cable actually works via COM5 in the emulator as the "real" port does on COM1 separate from your program. Use TeraTerm or PuTTy or HyperTerm or whatever terminal emulator you like. If all else fails try a different manufacturer.įirst what i would do is make sure you can talk through the USB-RS232 cable manually. (2) sometimes USB - RS232 converters made by lower-end manufacturers have problems. Unfortunately my home computer is running Linux so I can't recall where this setting is found. there is a way to set this higher, pretty easy once you find it. (1) the default Windows COM settings is preventing the use of any com ports numbers above a certain default number, typically "COM4". When ive had problems, its been for one of two reasons: Ive gone all the way up to COM16 or maybe higher. Generally, I've not had problems accessing any of the com ports that are assigned by USB-RS232 converters. Ive done a lot of work with COM ports, both real and virtual.
0 kommentar(er)
