SPI Timing Issue - NHD-0420D3Z-FL-GBW-V3

jfahlman

• March 22, 2016 09:07

Hello,

I am having a timing issue trying to send a full line (20 characters) to the display via SPI. I can write the characters fine however I must delay 100us between characters. I tried using the demo code below, but the delay_us(5) is too short. If I change to delay_us(100) it works but is too slow for my application:

case 2:                  // SPI
         spi_ss = 0;
         delay_cycles(5);
         for (ix = 0; ix < x; ix++) {
            SSPBUF = tx_packet[ix];
            while(!BF);
            temp = SSPBUF;
            delay_us(5);      // reduce effective clock rate
         }
         delay_cycles(5);
         spi_ss = 1;
         break;

The datasheet lists the execution time as 100us for the character write thus I was able to detemine that 100us was needed. Is this correct or is there something else I am doing wrong? Can the onboard PIC not buffer the 20 bytes transmitted, or I must indeed wait 100us for every byte transmitted?

Regards,
Jason

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  Saurabh_B

  • March 23, 2016 09:07

  Hi,
  
  It will take 100 µs (Max) to execute a write instruction. This means that you will have to wait 100µs between character writes. The 5µs is the wait to generate the longer clock pulse.

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