| ??? 08/04/09 08:29 Read: times |
#168125 - USB, COM, LPT - Use and abuse Responding to: ???'s previous message |
David Prentice said:
In my experience all of these cables will work with any programmers that make regular use of the RS232 e.g. send and receive ASCII strings. After all this is what RS232 as designed for. Absolutely; but not restricted to ASCII strings - normal binary comms should also work. Those programmers that bit-bang the RS232 control signals like DTR, RTS, CTS, DCD etc may not work. Exactly; this was always an abuse of the COM port! I said:
it's often not the USB-to-Serial that's to blame; it's the fault of poor application software that is making unwarranted assumptions about the device - such as trying to directly access hardware registers and/or bit-bang timing on the modem-control lines...
http://www.8052.com/forum/read/168090 David Prentice said:
Those "parallel port" programmers that bit-bang the control lines will probably never work with USB->LPT cables. Almost certainly: the USB->LPT cables you buy from "computer" stores are really just USB-to-Printer adaptors - they do not even claim to emulate the extra features required to use the LPT port as a general IO port. There are a few specialist adaptors that do claim to provide full (or, at least, fuller) LPT support; eg, see http://www.8052.com/forum/read/118809 - but, as you say, the cost may well not be worth it! And, of course, any PC application software that tries to hack the hardware registers directly is unlikely to work properly - if at all - on recent Windows version (ie, NT and later?) |
