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Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
21 years ago

uart

hi all,

has anybody seen a problem where bit 7 received for incoming characters appears wrong?

using a niosii 50MHz and adding a uart with 9600 8,n,1 hooking it up to Hyperterminal on windows pc

with the following running on the nios...

FILE *fp;

fp = fopen(UART1_NAME, "r+");

if(fp == NULL)

{

printf("error opening dev/uart1\n");

}

else

{

while(1)

{

printf("%c", getc(fp));

}

}

looking at the console in the IDE I see the following... (any character I type sometimes appears with bit 7 set to 1 and thus the garbage character)?

aaáaáaáa

eeåeåeåeå

iiéiéiéiéiéiéiéiéiéiéiéiéié

ooïoïoïoïoïoïoïoïoïoïo

uuõuõuõuõuõu

qqñqñqñqñqww÷w÷w÷w÷w÷w÷eeåeåeå

there is even some pattern to it..... if I press a "new" character i get it 1st two taps on the keyboard - after that the bit 7 received by the NIOS toggles for each one?

Thanks for any advice!!!

Regards,

Joe

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    21 years ago

    This looks suspiciously like the UART baud divisor is incorrect. The divisor is calculated based on the clock speed you enter into SOPC Builder at system-generation-time. You might make sure that your SOPC Builder system is re-generated & quartus project re-compiled (to ensure that the baud divisor is properly set in the FPGA), and then that your oscillator/PLL is driving 50Mhz, not 50.02 or 49.98....

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    21 years ago

    The Nios Uart is fine! The divisor is set correctly,etc.

    The problem is with the HyperTerminal program. While I can send entire text files down to the Nios without a problem, that behaviour I mentioned with the same characters still occurs..... crazy.

    I tried an old DOS terminal program in a DOS-box and it behaves fine!!

    Thanks for your attention though!

    http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/biggrin.gif

    ps. any recommended Terminal programs out there for Windoze?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    21 years ago

    How often will you be talking to your system via the uart? If the answer is alot you may want to create your own software to talk to it. Then you can make it do whatever you want (like file I/O for example).

    What were your connection settings in Hyperterminal? Usually that program is stable and this sounds bad. If your bit 7 is set then I would expect those funny characters (part of the extended ASCII set).
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    21 years ago

    Yes, that teraterm program work okay.

    For the record, I have tried my experiment several times with hyperterminal - setting it for 9600, n,8,1 with no flow control,etc..... (same settings as with the DOS program and this new teraterm).... also no terminal emulation (TTY) is selected.

    As I say - complete files can be transferred etc without a problem - only by tapping the same key (tap as fast or slow as you like!) will give the toggling bit 7 after the first two new characters.....!

    Thanks for all the help.

    http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/smile.gif