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How to transmit characters/special characters over SPI?

 
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Jeetdesai



Joined: 05 Jul 2018
Posts: 18

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How to transmit characters/special characters over SPI?
PostPosted: Tue Jul 10, 2018 8:44 am     Reply with quote

I can successfully transmit decimal, hex and binary data over SPI. I check my signals by connecting the oscilloscope probes at the data out, clock and enable pins, and observe the waveforms.

But i'm getting the wrong data when I send characters(A, B ... Z)) or special characters(!, @ ... +). The waveform on the output is the same (01100111) for all alphabetic characters and special characters.

The following is my code:

Code:
#include <18F87K22.h> 
#FUSES INTRC_IO                  //Internal RC Osc, no CLKOUT
//#FUSES NOPUT                     //No Power Up Timer
#FUSES NOPROTECT                 //No code protected from reads
#FUSES MCLR                      //Master Clear pin enabled
#FUSES NOCPD                     //No EE protection
#FUSES NOBROWNOUT                //No brownout reset
//#FUSES BROWNOUT                  // Hold in reset during brownout - else can corrupt EEPROM, act strange, etc
#FUSES NOIESO                    //Internal External Switch Over mode disabled
#FUSES NOFCMEN                   //Fail-safe clock monitor disabled   
#use delay(clock = 1000000)   
#define CS Pin_H0
//#BYTE ODCON1=
//#BIT  ODCON1BIT7 = ODCON1.7

/*#define SPI_MODE_0  (SPI_L_TO_H | SPI_XMIT_L_TO_H)
#define SPI_MODE_1  (SPI_L_TO_H)
#define SPI_MODE_2  (SPI_H_TO_L)
#define SPI_MODE_3  (SPI_H_TO_L | SPI_XMIT_L_TO_H) */

//========================================
void main()
{

setup_spi(SPI_MASTER | SPI_H_TO_L| SPI_CLK_DIV_64);

while(1)
  {
   output_low(CS);

   //spi_write(0x55); //hex data
   //spi_write(75); // decimal
   //spi_write(0b11110000); // binary
   spi_write("A"); //Char data
 
   output_high(CS);
   delay_us(1000);
   
  }

}
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue Jul 10, 2018 9:34 am     Reply with quote

Quote:
spi_write("A"); //Char data
This is not the correct way to do it.

The correct way is to use single quotes:
Code:
spi_write('A');
Jeetdesai



Joined: 05 Jul 2018
Posts: 18

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PostPosted: Tue Jul 10, 2018 9:46 am     Reply with quote

Thanks You so much !!!
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