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PostPosted: Wed Oct 18, 2006 23:42 
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Joined: Wed Oct 18, 2006 21:12
Posts: 1
Location: South Florida
SparkFun's Nokia knock-off uses a 9 bit serial word. I looked at code examples for this and it just didn't make sense to use built-in SPI features to send 8 bits then change the port to a logic port and bit bang out 1 bit. So here's the bit bang C function I used to send the 9 bit serial word.

Code:
void sdata9 (unsigned int dat9)             // dat9 is 9bits sent MSB first
{
unsigned char i;
unsigned int mag = 256;                     // mag=(256,128,64,32,16,8,4,2,1)

for (i=9; i>0; i--)                         // count bits 9 to 1
   {
   SCLK=0;                                  // serial clock pin low
   if (dat9 >= mag)                         // is dat9 greater than mag?
      {      
      dat9 = dat9-mag;                      // if yes subtract mag
      SDATA=1;                              // if yes data output pin high
      }
      else SDATA=0;                         // if no data output pin low
   mag = mag>>1;                            // divide by 2, next magnitude
   SCLK=1;                                  // serial clock pin high
   }                                        // loop back for next bit
}


Example:
Send display "common scan" 80 to 1 and 160 to 81.
Command is a 0 and Data is a 1. Same as A0 bit.

    sdata9(0x0BB); // send display Comand BB
    sdata9(0x103); // send display Data 03

C doesn't make the most perfect timing signals. Here's the same thing with a do nothing operation to add a few dozen nSec to make sure timing is at least double the minimum spec of the display when clocking at 50 MIPS.

Code:
void sdata9 (unsigned int dat9)
{
unsigned char nop;
unsigned char i;
unsigned int mag = 256;

nop = nop>>1;                   // NOP do nothing but waist time !
for (i=9; i>0; i--)
   {
   SCLK=0;
   if (dat9 >= mag)
      {
      dat9 = dat9-mag;
      SDATA=1;
      }
      else SDATA=0;
   mag = mag>>1;
   SCLK=1;
   nop = nop<<1;                // NOP do nothing but waist time !
   }
}


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