Lpc2000

icapapindi wrote:

>Can I do it with PLL_MULT=1? I use the Xtal frecuency without PLL, I'm
>using these values:
>
>PCLK = 10 Mhz
>Divisor = 4
>MULVAL = 14
>DIVAddVal = 5
>
>With these values It is suppose to get 115.131 bps, but when I test
>with the oscilloscope the frecuency is about 128 Kbps. The code I used is:
>---------------------------------------------------
>unsigned int divisor=5;
>UART1_LCR = 0x83; /* 8 bit, 1 stop bit, no parity, enable DLAB */
>UART1_FDR=(UART1_FDR & 0xFFFFFF00) | 0xE5;
>UART1_DLL = divisor & 0xFF;
>UART1_DLM = (divisor >> 8) & 0xFF;
>UART1_LCR &= ~0x80; /* Disable DLAB */
>PCB_PINSEL0 = PCB_PINSEL0 & ~0x0F0000 | 0x050000;
>UART1_FCR = 1;
>----------------------------------------------------
>
>  
>
I worked my way through the example given in the LPC2138 User Manual and 
I came up with this little perl program.  Perhaps others may find it useful:

=============== begin baudrate.pl =================
#!/usr/bin/perl
# this determines the degree of error between desired and actual
# baudrates on the LPC2000 processors.
#    UART_BAUD(baud) (uint16_t)((PCLK / ((baud) * 16.0)) + 0.5)

my $FREQ = 14745000;    # crystal on X1 X2 pins.
my $PLL_MUL = 4;  # pll mult value.
my $PBSD = 2;     # peripheral bus divider.
my $CCLK = ($FREQ * $PLL_MUL);
my $PCLK = ($CCLK / $PBSD);
my @commonRates = 
(300,600,1200,2400,4800,9600,19200,38400,57600,115200,230400);

sub calcBaud {
my $desired = $_[0];
my $divisor = int(($PCLK / ($desired*16.0))+ 0.5);
my $actual = int(($PCLK / (16*$divisor)) * 1000) / 1000;
my $error = int((($actual - $desired) / $desired) * 1000000) / 10000;
   print "divisor: ${divisor}  desired: ${desired}  ".
      "actual: ${actual}  error: ${error}%\n";
}

   print "Crystal: ${FREQ}\n";
   print "PLL MULT: ${PLL_MUL}\n";
   print "Periph Bus Div: ${PBSD}\n";
   while (@commonRates) {
      calcBaud (shift(@commonRates));
   }

================ snip ========================




-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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