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SPI Master Slave Communication

I am into a project where I need 2 establish communication between ADuc814(Master) and ADuc841(Slave). Master shud Receive data transmitted by Slave. I am unable to establish the comm. I feel there is no response 4rm slave as though master generates the clock and SS pin is low, slave does not response.
Is it necessary that both master and slave should operate in same CLOCK??
For Hardware connection, MOSI, MISO, SCLK and SS pins of Master and Slave are connected.
Foll is the code
Master Code

#include <ADUC814.H>
unsigned char Data[20]; //Store SPI Rx data in Memory
void Uart_Tx(unsigned char AsciData); //Serial Tx
sbit SS = 0xB5;
void main()
{
  char i;
  PLLCON = 0x00; //Core Clk = 16.6777MHz
 //////////baud 0f 4800////////
  RCAP2H = -1; RCAP2L = 0x92;
  TH2 = -1;    TL2 = 0x92;
  SCON = 0x50; T2CON = 0x34;
 //////////////////////////////

  CFG814 = 0x01; // Enable P3.5,6,7 for SPI
  SPICON = 0x37; // Master, CPOH=1,CPOL=0
  SS = 0; // Slave Select Enable
  for(i=0;i<20;i++)
  { SPIDAT = 0x00; // SPI Clock Generate
    while(!ISPI); ISPI = 0;
    Data[i] = (unsigned char)SPIDAT;
  }

 /////////Serial Tx SPI Data into UART//////////
  for(i=0;i<20;i++)
  { Uart_Tx(Data[i]); Uart_Tx('\n'); }
 /////////////////////////////////////////////
}

Slave Code, ADuC841

void main()
{ char i;
  SPICON = 0x24; // Slave, CPOH=1, CPOL=0
  for(i=0;i<20;i++)
  { SPIDAT = 0x38; /*Transmit Dummy Data, Asci of '8'
    while(!ISPI); ISPI = 0; }

}


Friendzzzz Please Help.........

Parents
  • Although this might not be what your problem is, you might as well eliminate it as a potential source...

    You said "Even SS pin is low throughout" so does that mean it is always low like it is shown in your 'master' code?

    I recommend that you insert the SS appropriately between byte transfers. The data-sheet on the ADuC814 indicates that the SS line should be low 'during the byte communication.' (The implication being that it was and/or should return to high otherwise).

    If there is a timing issue, the SS line might be used to reset (or re-initialize) the internal state-machine associated with the bit-level transfers.

    #include <ADUC814.H>
    unsigned char Data[20]; //Store SPI Rx data in Memory
    void Uart_Tx(unsigned char AsciData); //Serial Tx
    sbit SS = 0xB5;
    void main()
    {
      char i;
      PLLCON = 0x00; //Core Clk = 16.6777MHz
     //////////baud 0f 4800////////
      RCAP2H = -1; RCAP2L = 0x92;
      TH2 = -1;    TL2 = 0x92;
      SCON = 0x50; T2CON = 0x34;
     //////////////////////////////
    
      CFG814 = 0x01; // Enable P3.5,6,7 for SPI
      SPICON = 0x37; // Master, CPOH=1,CPOL=0
      SS = 1; // Slave Select Disable // <===== Alter to 1
      for(i=0;i<20;i++)
      {
        SS = 0; // Slave Select Enable // <===== ADD
        SPIDAT = 0x00; // SPI Clock Generate
        while(!ISPI); ISPI = 0;
        SS = 1; // Slave Select Disable// <===== ADD
        Data[i] = (unsigned char)SPIDAT;
      }
    
     /////////Serial Tx SPI Data into UART//////////
      for(i=0;i<20;i++)
      { Uart_Tx(Data[i]); Uart_Tx('\n'); }
     /////////////////////////////////////////////
    }
    

Reply
  • Although this might not be what your problem is, you might as well eliminate it as a potential source...

    You said "Even SS pin is low throughout" so does that mean it is always low like it is shown in your 'master' code?

    I recommend that you insert the SS appropriately between byte transfers. The data-sheet on the ADuC814 indicates that the SS line should be low 'during the byte communication.' (The implication being that it was and/or should return to high otherwise).

    If there is a timing issue, the SS line might be used to reset (or re-initialize) the internal state-machine associated with the bit-level transfers.

    #include <ADUC814.H>
    unsigned char Data[20]; //Store SPI Rx data in Memory
    void Uart_Tx(unsigned char AsciData); //Serial Tx
    sbit SS = 0xB5;
    void main()
    {
      char i;
      PLLCON = 0x00; //Core Clk = 16.6777MHz
     //////////baud 0f 4800////////
      RCAP2H = -1; RCAP2L = 0x92;
      TH2 = -1;    TL2 = 0x92;
      SCON = 0x50; T2CON = 0x34;
     //////////////////////////////
    
      CFG814 = 0x01; // Enable P3.5,6,7 for SPI
      SPICON = 0x37; // Master, CPOH=1,CPOL=0
      SS = 1; // Slave Select Disable // <===== Alter to 1
      for(i=0;i<20;i++)
      {
        SS = 0; // Slave Select Enable // <===== ADD
        SPIDAT = 0x00; // SPI Clock Generate
        while(!ISPI); ISPI = 0;
        SS = 1; // Slave Select Disable// <===== ADD
        Data[i] = (unsigned char)SPIDAT;
      }
    
     /////////Serial Tx SPI Data into UART//////////
      for(i=0;i<20;i++)
      { Uart_Tx(Data[i]); Uart_Tx('\n'); }
     /////////////////////////////////////////////
    }
    

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