Revision 2:e1781d02ec0d, committed 2011-02-18

Comitter:

bobanderson

Date:

Fri Feb 18 02:36:18 2011 +0000

Parent:

1:ecca38babc13

Commit message:

Rev to allow either MPC3304 or MPC3208 A/D converters to be used.

Changed in this revision

--- a/main.cpp	Fri Feb 18 00:43:05 2011 +0000
+++ b/main.cpp	Fri Feb 18 02:36:18 2011 +0000
@@ -40,26 +40,30 @@
 
 AnalogIn ain( p20 );
 
-DigitalOut mpc3304Select(p8);
+DigitalOut extAdcSelect(p8);
 DigitalOut led4(LED4);
 
 SPI spi(p5,p6,p7);             // spi(mosi,miso,sck)
 
+#define MCP3208  // or MCP3304
+
+#define EXT_ADC_CHAN 5
+
 #define NUM_SAMPLES 1000000
 #define HGRAM_MAX_INDEX 60
 
 int histoGramA[ HGRAM_MAX_INDEX + 1 ];  // histogram array for internal ADC
 int histoGramB[ HGRAM_MAX_INDEX + 1 ];  // histogram array for (possible) external ADC
 
-int glitchCount = 0;
+int  glitchCount = 0;
 bool glitchSuppressionWanted = false;
 bool useExternalADC = false;
 
 void setADCclockToMaxConversionRate( void );
 int  glitchSuppressedAnalogIn( bool );
-int  readExternalADC( void );
+int  readExternalADC( int );
 void displayMenu( void );
-int getCenterValue( bool externalADC );
+int  getCenterValue( bool externalADC );
 
 int max( int a, int b ) {
     if ( a > b ) return a;
@@ -90,7 +94,7 @@
     
     led4 = 0;  // This led shows progress during data acquisition.
     
-    mpc3304Select = EXT_ADC_OFF;  // deselect
+    extAdcSelect = EXT_ADC_OFF;  // deselect
     
     spi.format( 8, 0 );
     spi.frequency( 500000 );
@@ -127,7 +131,7 @@
                 
               case 't':
                 for ( int cnt = 0; cnt < 50; cnt++ )
-                   printf( "EXT ADC = %d\r\n", readExternalADC() );
+                   printf( "EXT ADC = %d\r\n", readExternalADC(EXT_ADC_CHAN) );
                 break;
              
               case 's':
@@ -160,7 +164,7 @@
         led4 = 0;
  
         int glitchCountInternal = glitchCount;
-        int glitchCountExternal;
+        int glitchCountExternal = 0;
         
         if ( useExternalADC )
         {
@@ -183,11 +187,9 @@
             led4 = 0;
             
             glitchCountExternal = glitchCount;
-        }
-        
+        }      
         
-        
-        // Output histoGram
+        // Output histoGram(s)
         for ( int j = 0; j <= HGRAM_MAX_INDEX; j++ ) {
             if ( useExternalADC )
                 printf( "%4d %8d %8d\r\n", j - (HGRAM_MAX_INDEX/2), histoGramA[j], histoGramB[j] );
@@ -195,6 +197,7 @@
                 printf( "%4d %8d\r\n", j - (HGRAM_MAX_INDEX/2), histoGramA[j] );
         }
         
+        // Show glitch stats if glitch suppression was enabled
         if ( glitchSuppressionWanted ) {
             if ( useExternalADC )
                 printf( "\nglitchCount: Internal =  %d  External = %d\r\n", 
@@ -224,7 +227,7 @@
     int v1,v2,delta;
     
     if ( externalADC )
-        v1 = readExternalADC();
+        v1 = readExternalADC(EXT_ADC_CHAN);
     else    
         v1 = ain.read_u16() >> 4;
         
@@ -236,7 +239,7 @@
     // within the tolerance band --- i.e., no glitch
     while(1){
         if ( externalADC )
-            v2 = readExternalADC();
+            v2 = readExternalADC(EXT_ADC_CHAN);
         else
             v2 = ain.read_u16() >> 4;
         delta = v1 - v2;
@@ -246,12 +249,24 @@
     }
 }
 
-int readExternalADC( void ) {  // Hardcoded for channel 0 (for quick test)
-    mpc3304Select = EXT_ADC_ON;
-    int byte1 = spi.write( 0xc  );        // start=1  sgl=1 d2=0 d1=0
-    int byte2 = spi.write( 0x0  ) & 0xf;  // d0 = 0
+int readExternalADC( int channel ) {
+    int ch = channel & 0x7;
+    extAdcSelect = EXT_ADC_ON;
+    
+    #ifdef MCP3208
+        int byte1 = spi.write( 0x6 | (ch >> 2) );
+        int byte2 = spi.write( (ch << 6) ) & 0xf;  // d0 = 0
+    #else
+      #ifdef MCP3304
+          int byte1 = spi.write( 0xc | (ch >> 1) );
+          int byte2 = spi.write( (ch << 7) ) & 0xf;  // d0 = 0
+      #else
+          error( "Undefined external ADC device" );
+      #endif
+    #endif      
+                
     int byte3 = spi.write( 0xaa );        // dummy value, but nice pattern of logic analyzer
-    mpc3304Select = EXT_ADC_OFF;
+    extAdcSelect = EXT_ADC_OFF;
     int value = (byte2 << 8) | byte3;
     //printf( "byte2 = %2x  byte3 = %2x  value = %d\r\n", byte2, byte3, value );
     return value;