Three-speaker Chladni Patterns

Team Members

• Christopher Chow (Mechanical Engineering, Class of 2010)
• Anup Tapase (Electrical Engineering, Class of 2010)
• Lingyu Xie (Electrical Engineering, Class of 2009)

Code

#include <18f4520.h>
#DEVICE ADC=8                   // set ADC to 8 bit accuracy
#use delay(clock=40000000)
#include "flex_lcd.c"             //must include in order to output to LCD
#use spi(DO = PIN_A3, CLK = PIN_A2, ENABLE = PIN_A1, BITS = 16, MASTER, ENABLE_ACTIVE = 0, MSB_FIRST, IDLE = 1)

int16 freq,target_freq;
int16 target_freq_reg, old_target_freq_reg;
int8 knob_val=0;

void check_input();

void main()
{
   int16 ct;
   
   target_freq_reg=2000+16384;         // initialize starting frequency of speakers to 298 Hz (non-resonant)
   old_target_freq_reg=2000+16384;     // set old target freq variable to equal target freq

   setup_adc_ports(AN0);               // Set up analog input port as pin A0
   setup_adc(ADC_CLOCK_INTERNAL);
   
   lcd_init();  // Always call this first.
   
   //INITIAL FREQUENCY FOR AD9833
   spi_xfer(0b0010000100000000); //format command, output sine wave
               
   spi_xfer(target_freq_reg);    //1st set of bits, 14 LSB, this range is good enough for our use
                                 //send the target frequency register value (freq + 16384) to AD9833 chip
   spi_xfer(0b0100000000000000); //2nd set of bits, 14 MSB
   
   spi_xfer(0b1100000000000000); //phase register: 0 phase shift (B0-B13)
   
   spi_xfer(0b0000000000000000); //unformat
   
   freq=(float).149011 * (float)(target_freq_reg - 16384);  //convert the target freq register value to actual freq value
   target_freq=freq; // initialize target freq as current freq

   printf(lcd_putc,"\fFreq: %Lu\n",freq); //display current freq
   printf(lcd_putc,"Target: %Lu\n",target_freq); //display target freq
   
   while(TRUE)
   {
      check_input(); //check the knob input to see if target frequency has changed
      
      if(old_target_freq_reg != target_freq_reg) //go in here if target freq changed after calling check_input()
      {
         if(target_freq_reg > old_target_freq_reg) //sweep up to target freq
         {
            for(ct=old_target_freq_reg; ct<=target_freq_reg; ct=ct+7)
            {
               spi_xfer(0b0010000100000000);
               
               spi_xfer(ct); //set AD9833 frequency to ct, which is freq register that is sweeping up by 7 each time loop is run
               spi_xfer(0b0100000000000000);
               
               spi_xfer(0b1100000000000000);
               
               spi_xfer(0b0000000000000000);
               
               freq=(float).149011 * (float)(ct - 16384);
               target_freq=(float).149011 * (float)(target_freq_reg - 16384);
         
               printf(lcd_putc,"\fFreq: %Lu\n",freq); //display current freq
               printf(lcd_putc,"Target: %Lu\n",target_freq); //display target freq
               
               check_input(); //see if knob position has selected different target freq
               delay_ms(90);  //delay to allow speakers to play freq for 90 ms + 10 ms (in check_input() function)
            }
               
            old_target_freq_reg = target_freq_reg; //reached target freq, set both variables equal until knob position changed
               
         }
         else if(target_freq_reg < old_target_freq_reg) //sweep down to target freq
         {
            for(ct=old_target_freq_reg; ct>=target_freq_reg; ct=ct-7)
            {
               spi_xfer(0b0010000100000000);
               
               spi_xfer(ct); //set AD9833 frequency to ct, which is freq register that is sweeping down by 7 each time loop is run
               spi_xfer(0b0100000000000000);
               
               spi_xfer(0b1100000000000000);
               
               spi_xfer(0b0000000000000000);
               
               
               freq=(float).149011 * (float)(ct - 16384); //convert current freq register value (ct) to frequency value
               target_freq=(float).149011 * (float)(target_freq_reg - 16384); //convert target freq register to target freq value
         
               printf(lcd_putc,"\fFreq: %Lu\n",freq); //display current freq
               printf(lcd_putc,"Target: %Lu\n",target_freq); //display target freq
               
               check_input(); //see if knob position has selected different target freq
               delay_ms(90);  //delay to allow speakers to play freq for 90 ms + 10 ms (in check_input() function)
            }
   
            old_target_freq_reg = target_freq_reg; //reached target freq, set both variables equal until knob position changed
         }
      }
   }
}

void check_input() //check knob position to see if target freq has changed
{      
      set_adc_channel(0);     // Set the analog input channel to 0
      delay_us(10);           // wait 10uS for ADC to settle to a newly selected input
      knob_val = read_adc();  // Read in knob user input to tell speakers what resonant freq to sweep up to
      
      delay_ms(10);           // delay 10 ms to allow reading of analog input
      
      //check and set target_freq_reg according to knob position (0-255 values split into 8 discrete levels)
      if (knob_val >= 0 && knob_val< 22 )
         target_freq_reg = 2281+16384; //339 Hz
      else if(knob_val >= 22 && knob_val< 54)
         target_freq_reg = 3308+16384; //493 Hz 
      else if(knob_val >= 54 && knob_val< 86)
         target_freq_reg = 3778+16384; //563 Hz
      else if(knob_val >= 86 && knob_val< 117)
         target_freq_reg = 3986+16384; //594 Hz
      else if(knob_val >= 117 && knob_val< 147)
         target_freq_reg = 4207+16384; //627 Hz 
      else if(knob_val >= 147 && knob_val< 178)
         target_freq_reg = 4362+16384; //650 Hz 
      else if(knob_val >= 178 && knob_val< 209)
         target_freq_reg = 5006+16384; //746 Hz 
      else if(knob_val >= 209 && knob_val< 239)
         target_freq_reg = 5308+16384; //791 Hz 
      else if(knob_val >= 239 && knob_val< 255)
         target_freq_reg = 5872+16384; //875 Hz 
}