#1
  1. Contributing User
    Devshed Newbie (0 - 499 posts)

    Join Date
    Mar 2003
    Location
    currently Lisbone, Portugal
    Posts
    154
    Rep Power
    12

    Exclamation C++ and RS232 port


    Welcome back,
    another question from a newbe.
    Has anyone experimented with programing RS232c port (standard serial port) of the computer?
    If so, what is the maximum transfer rate I can get from it? I was trying to get something like 250kb/s but something is definetely wrong with the transfer as the top I can get is 19200b/s.
    Oh, I must say I make alink to a Atmel uP.
    If anyone has any suggestions, please do.
    Thanks
    Marek:D
  2. #2
  3. No Profile Picture
    Contributing User
    Devshed Novice (500 - 999 posts)

    Join Date
    Jan 2002
    Location
    Seattle WA
    Posts
    863
    Rep Power
    14
    You won't get something like 250 kilobits...serial ports are limited to about the speed of a modem if I recall correctly. Could be that 19 kilobits is the limit of the interface, I just can't remember.
  4. #3
  5. Contributing User
    Devshed Newbie (0 - 499 posts)

    Join Date
    Mar 2003
    Location
    currently Lisbone, Portugal
    Posts
    154
    Rep Power
    12
    Hi
    strange thing because so far I have reached 128kbits without greater problems. I was just wondering if there is any possibility of doubling it any more. Seems that either 128kbits is the limit or that the uP I am using has such limit.
    Nevertheless, I had a suggestion today that LPT port is much simpler to cope with since it can handle 12 bit parallel transfer up to 10Mbits/sec and programming it is much easier.
    Well, today I will have a long night with C++ from what I see.
    Perhaps You have anything on programing LPT port under WIN 2000??
    Best wishes and thanks for the post
    Marek
    :D
  6. #4
  7. No Profile Picture
    Contributing User
    Devshed Novice (500 - 999 posts)

    Join Date
    Jan 2002
    Location
    Seattle WA
    Posts
    863
    Rep Power
    14
    Sorry, I've never really programmed anything in rs232 or lpt beyond toying around, so I don't have anything to really show you.

    If you were getting higher transfer rates, maybe you were using a protocol with text compression?
  8. #5
  9. Contributing User
    Devshed Newbie (0 - 499 posts)

    Join Date
    Mar 2003
    Location
    currently Lisbone, Portugal
    Posts
    154
    Rep Power
    12
    Welcome back :)
    The strange thing is that there is no compression.
    All I used was a 6.61MHz quarzt, 90AT8535LS uP, one meter cable for RS232c standard and that was all. No compression. All I was using was the Terminal within the Bascom AVR software and I made uplink on 128kbits. Since it was working fine and I did not get any errors, I assume that the link was actually running at such speed. Once I tried to switch to 256k, it stopped responding.
    Nevertheless, I have been sitting the whole night tryign to work out the LPT port and I think I have some good results about it. Once I have done something usefull, I will poresent it here so that everyone can have a look at it.
    Best wishes
    Marek

IMN logo majestic logo threadwatch logo seochat tools logo