Audio codec shield with Intel Edison

[youthreewire]

I also found this http://www.alsa-project.org/alsa-doc/alsa-lib/_2test_2latency_8c-example.html

[youthreewire]

Hello,

I came across a software SPI library recently.I want to use this in the Due. Earlier I used SPI like this:

Code: Select all

while((SPI0->SPI_SR & SPI_SR_TDRE)==0)
 {;}
 
  while ((SPI0->SPI_SR & SPI_SR_TXEMPTY) == 0);
  digitalWriteDirect(12, HIGH);
 SPI0->SPI_TDR = rout;
   //SPI0->SPI_TDR = lout;
  __asm__("nop");
  __asm__("nop");
  __asm__("nop");
  __asm__("nop");
  __asm__("nop");
  __asm__("nop");
  __asm__("nop");
  __asm__("nop");
  __asm__("nop");
  __asm__("nop");
  __asm__("nop");
 
 digitalWriteDirect(12, LOW);
 
 while((SPI0->SPI_SR & SPI_SR_TDRE)==0)
 {;}
 
 while((SPI0->SPI_SR & SPI_SR_RDRF) == 0)
 {;}
 lin = SPI0->SPI_RDR;
 delayMicroseconds(1);
  while((SPI0->SPI_SR & SPI_SR_RDRF) == 0)
 {;}
 rin = SPI0->SPI_RDR;


I am doing 16 bit SPI transfers.I want to do the same with the software SPI here.
http://www.iesensor.com/blog/2013/07/09/software-spi-library-for-arduino-tested-on-mega2560/

Code: Select all

#include <stdint.h>
    #define _MISO  40
    #define _MOSI  41
    #define _SCK   42
    #define _SS  12
   
    #define _CPOL 0
    #define _CPHA 1 
 
    #define SPI_MSBFIRST 1
   
    uint8_t spi_transfer(uint8_t b) ;
    void spi_setup();
   
    //#if  1//defined(__AVR_ATmega2560__)
      //for example 8cycles as one SPI period, for Arduino mega2560 16MHz, SPI 2MHz,  tested passed for AD7730!
      //for DUE 84MHz,  need longer nop cycles to keep waveform!  -> multiply each delay by 6
      #define DELAY_CYCLES  2     //more precise than micro second delay,  1/4 of SPI bus frequency , depends on MCU master clock,
      #define DELAY_CYCLES_P0  1  //propogation pre
      #define DELAY_CYCLES_P1  3  //propogation post
      #define DELAY_CYCLES_C0 1   //capture pre (SCK edge -> capture) usually smaller delay
      #define DELAY_CYCLES_C1 3   //capture post ( capture -> SCK edge)  usually bigger delay
    //#else
    //  #error "checking your board and MCU main frequency and set prooper delay for software_SPI bit-banging"
    //#endif
 
 // #endif

 
  /*
  The timing diagram is shown to the right. The timing is further described below and applies to both the master and the slave device.
 
      At CPOL=0 the base value of the clock is zero
          For CPHA=0, data is captured on the clock's rising edge (lowâ†'high transition) and data is propagated on a falling edge (highâ†'low clock transition).
          For CPHA=1, data is captured on the clock's falling edge and data is propagated on a rising edge.  ->  MODE1 for Arduino SPI lib
      At CPOL=1 the base value of the clock is one (inversion of CPOL=0)
          For CPHA=0, data is captured on clock's falling edge and data is propagated on a rising edge.
          For CPHA=1, data is captured on clock's rising edge and data is propagated on a falling edge.
  */

//#endif // header

//if SOFTWARE_SPI

  static inline void delayCycles(int cycles)
  {
      for (int i=0; i++; i<cycles)
          __asm__("nop\n\t");
         // __nop();
  }
 
 
  //#if SPI_MSBFIRST
    unsigned char msk[] = {0x80, 0x40, 0x20, 0x10, 0x8, 0x4, 0x2, 0x1};
    #define PCK() (bits[0] << 7 | bits[1] << 6 | bits[2] << 5 | bits[3] << 4 | bits[4] << 3 | bits[5] << 2 | bits[6] << 1 | bits[7])
  //#else
    //unsigned char msk[] = {0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80};
    //#define PCK() (bits[0]  | bits[1] << 1 | bits[2] << 2 | bits[3] << 3 | bits[4] << 4 | bits[5] << 5 | bits[6] << 6 | bits[7]<<7)
 // #endif
 
 
 
  void spi_setup()
  {
    pinMode(_SS, OUTPUT);
    pinMode(_MISO, INPUT);
    pinMode(_MOSI, OUTPUT);
    pinMode(_SCK, OUTPUT);
    //
     digitalWrite(_SS, HIGH);
    #if _CPOL
     digitalWrite(_SCK, HIGH);
    #else
     digitalWrite(_SCK, LOW);
    #endif
  }
 
  // chip selection has been declared outside
  inline void spi_select() {digitalWrite(_SS, LOW);}
  inline void spi_unselect() {digitalWrite(_SS, HIGH);}
 
  //mode 0: SCK idle low, phase: reading at middle of SCK HIGH pulse
  //mode 1: SCK idle low, phase: reading at middle of SCK LOW pulse
  //this big-bang should work for both  CPHA=1  and CPHA=0
  uint8_t spi_transfer(uint8_t b)
  {
    uint8_t reply=0;
    char bits[8] = {0, 0, 0, 0, 0, 0, 0, 0};  //reading buffer
 
    /*  hardware SPI
    SPDR=b;
    spi_wait();
    reply = SPDR;
    return reply;*/
 
      //cli();  it will cause error on Arduino, most of SPI should be interrupt tolerable
      //spi_select(); // should be called outside, may be required by one transition
      delayCycles(DELAY_CYCLES);   // checking timing characteristics, need delay from CS to rising edge?
      // here, delay is added, to make CPHA=1 and CPHA=0 both work!
     
      for(uint8_t _bit = 0;_bit < 8;_bit++)
      {
      #if _CPHA
        #if _CPOL
          digitalWrite(_SCK, LOW);  //  propagation at rising edge
       #else
          digitalWrite(_SCK, HIGH);  // change this to LOW for CPOL=1
       #endif
          digitalWrite(_SCK, HIGH);  // change this to LOW for CPOL=1
          delayCycles(DELAY_CYCLES_P0);   
     
          digitalWrite(_MOSI, !!(b & msk[_bit]));
          delayCycles(DELAY_CYCLES_P1); //  propagation
       #if _CPOL
         digitalWrite(_SCK, HIGH);  // data will be captured at falling edge
       #else
          digitalWrite(_SCK, LOW); 
       #endif
         delayCycles(DELAY_CYCLES_C0); // holding low, so there is enough time for data preparation and changing
     
         bits[_bit] = digitalRead(_MISO); // reading at the middle of SCK pulse
         delayCycles(DELAY_CYCLES_C1);  // wait until data is fetched by slave device,  while SCK low, checking DATAsheet for this interval
     
      #else
          // changing MOSI big while SCK low, propogation
          digitalWrite(_MOSI, !!(b & msk[_bit]));
          delayCycles(DELAY_CYCLES_P1); // there is a requirement of LOW and HIGH have identical interval!
 
        #if _CPOL
         digitalWrite(_SCK, LOW);
        #else
         digitalWrite(_SCK, HIGH);
        #endif
         delayCycles(DELAY_CYCLES_C0);    //
     
         bits[_bit] = digitalRead(_MISO); // reading at the middle of SCK pulse
         delayCycles(DELAY_CYCLES_C1);  // wait until data is fetched by slave device,  while SCK high, checking DATAsheet for this interval
       
        #if _CPOL
          digitalWrite(_SCK, HIGH);
        #else
         digitalWrite(_SCK, LOW);  // data will change at falling edge
        #endif
         delayCycles(DELAY_CYCLES_P0); // holding low, so there is enough time for data preparation and changing
     
      #endif
 
      }
     delayCycles(DELAY_CYCLES);  // checking timing characteristics, it is no needed by AD7730, from CS to rising edge
     // spi_unselect(); 
 
      //sei();  // it will cause error on Arduino, most of SPI should be interrupt tolerable
 
     reply = PCK();
 
    return reply;
 
  }

//#endif

uint8_t temp1;
void setup( )
{
  spi_setup( );
}

void loop( )
{
  spi_transfer(temp1);
}


How shall I do it?

[guest]

what doesnt work about the software SPI library? you will probably have to change how the SS pin operates

[youthreewire]

I was able to get the software SPI (i.e SCK pin wave) sync with the SS pin wave at the first bit.I will see if I am getting any sound from the codec at this point and then will later try and replicate the same in edison.

[youthreewire]

shot2.jpg (50.39 KiB) Viewed 24666 times

shot1.jpg (46.87 KiB) Viewed 24666 times

The above are my oscilloscope shots for the SS pin (yellow) and SCK pin(green).The first SCK pulse is actually little wider in width.Will it work?

[guest]

looks good, should work

[youthreewire]

Software SPI is working on the Due . Now I will try and replciate it on the edison.

[youthreewire]

The earlier result is not a true result because the "bypass" flag was set to 1.The following is my ISR function which runs at 44 khz or 8khz (as per the specified frequency).

Code: Select all

void TC8_Handler()
{
 ledon1 = !(ledon1);
 digitalWrite(13, ledon1);

  linh = spi_transfer(lout>>8,1);
  linl = spi_transfer(lout,2);
 lina[myi]=(linh << 8)|(linl & 0xff);
}


All I get is a cracking sound. I do not know if I am doing it right with the bit shifts and SPI transfers

[guest]

looking at your picture again, there are 9 pulses on the first transfer. there should only be 8.

[youthreewire]

Yea I corrected the 9 pulses thing to 8. But still I get crackling sound. I wonder what is wrong.Is the folowing piece of code right?

Code: Select all

void TC8_Handler()
{
  linh = spi_transfer(lout>>8,1);
  linl = spi_transfer(lout,2);
 lina[myi]=(linh << 8)|(linl & 0xff);
}

Can you implement the same software SPI on your arduino (it should run on atmega328 arduino as well) and let me know.I will then port it to Due and Edison.