UART COMMUNICATION

Hi,

My Virtex II Pro board is connected to the hyperterminal through RS232. My VHDL code receives a character from hyperterminal, then sends back to hyperterminal. The problem is that the returned character is diferrent from the typed character. For example, when I type "a", I get "h" as returned character, consistently.
It seems that the four most significant bits stay the same and only the four least significant bits change. I am 100% sure my transmission code is ok. Also, testing RS 232 cable (using Oscilliscope), the same typed character enters the board. The problem must be in RX code.

Any idea or experience with this kind of problems ? Thanks

Comments

  • : Hi,
    :
    : My Virtex II Pro board is connected to the hyperterminal through RS232. My VHDL code receives a character from hyperterminal, then sends back to hyperterminal. The problem is that the returned character is diferrent from the typed character. For example, when I type "a", I get "h" as returned character, consistently.
    : It seems that the four most significant bits stay the same and only the four least significant bits change. I am 100% sure my transmission code is ok. Also, testing RS 232 cable (using Oscilliscope), the same typed character enters the board. The problem must be in RX code.
    :
    : Any idea or experience with this kind of problems ? Thanks
    :


    Hard to tell, but it sounds a bit like wrong baudrate settings. Perhaps the calculated baudrate isn't accurate enough, or something like that.
  • : : Hi,
    : :
    : : My Virtex II Pro board is connected to the hyperterminal through RS232. My VHDL code receives a character from hyperterminal, then sends back to hyperterminal. The problem is that the returned character is diferrent from the typed character. For example, when I type "a", I get "h" as returned character, consistently.
    : : It seems that the four most significant bits stay the same and only the four least significant bits change. I am 100% sure my transmission code is ok. Also, testing RS 232 cable (using Oscilliscope), the same typed character enters the board. The problem must be in RX code.
    : :
    : : Any idea or experience with this kind of problems ? Thanks
    : :
    :
    :
    : Hard to tell, but it sounds a bit like wrong baudrate settings. Perhaps the calculated baudrate isn't accurate enough, or something like that.
    :

    You may be right. The receiving buadrate is 19212 HZ and hyperterminal baudrate is 19200 HZ. But, I am reading the incomming bit in the middle of bit time. This will take care of slight baudrate difference.
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