Diff: main.cpp

Revision:

0:dd98f6992fa6

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Jun 16 15:42:09 2013 +0000
@@ -0,0 +1,67 @@
+/* Program Example 14.5: A bar graph meter for ADC input, using control registers to set up ADC and digital I/O                         
+                                                       */
+// variable declarations                                              
+char ADC_channel=1;     // ADC channel 1
+int  ADCdata;           //this will hold the result of the conversion
+int DigOutData=0;       //a buffer for the output display pattern
+
+// function prototype                                              
+void delay(void);
+
+//define addresses of control registers, as pointers to volatile data 
+//(i.e. the memory contents)
+#define PINSEL1        (*(volatile unsigned long *)(0x4002C004))
+#define PCONP          (*(volatile unsigned long *)(0x400FC0C4))
+#define AD0CR          (*(volatile unsigned long *)(0x40034000))
+#define AD0GDR         (*(volatile unsigned long *)(0x40034004))
+#define FIO2DIR0       (*(volatile unsigned char *)( 0x2009C040))
+#define FIO2PIN0       (*(volatile unsigned char *)( 0x2009C054))  
+
+int main() {
+  FIO2DIR0=0xFF;// set lower byte of Port 2 to output, this drives bar graph
+
+//initialise the ADC
+  PINSEL1=0x00010000; //set bits 17-16 to 01 to enable AD0.1 (mbed pin 16)
+  PCONP |= (1 << 12);                // enable ADC clock
+  AD0CR =   (1 << ADC_channel)       // select channel 1 
+           | (4 << 8)       // Divide incoming clock by (4+1), giving 4.8MHz
+           | (0 << 16)      // BURST = 0, conversions under software control  
+           | (1 << 21)      // PDN = 1, enables power
+           | (1 << 24);     // START = 1, start A/D conversion now 
+  
+  while(1) {                      // infinite loop
+    AD0CR = AD0CR | 0x01000000;   //start conversion by setting bit 24 to 1,
+                                                               //by ORing
+    // wait for it to finish by polling the ADC DONE bit         
+    while ((AD0GDR & 0x80000000) == 0) {  //test DONE bit, wait till it’s 1
+    }
+    ADCdata = AD0GDR;            // get the data from AD0GDR
+    AD0CR &= 0xF8FFFFFF;         //stop ADC by setting START bits to zero
+   // Shift data 4 bits to right justify, and 2 more to give 10-bit ADC 
+   // value - this gives convenient range of just over one thousand. 
+    ADCdata=(ADCdata>>6)&0x03FF;    //and mask      
+    DigOutData=0x00;                //clear the output buffer
+    //display the data
+    if (ADCdata>200)
+      DigOutData=(DigOutData|0x01);  //set the lsb by ORing with 1
+    if (ADCdata>400)
+      DigOutData=(DigOutData|0x02);  //set the next lsb by ORing with 1
+    if (ADCdata>600)
+      DigOutData=(DigOutData|0x04);
+    if (ADCdata>800)
+      DigOutData=(DigOutData|0x08);
+    if (ADCdata>1000)
+      DigOutData=(DigOutData|0x10);   
+      
+    FIO2PIN0 = DigOutData;        // set port 2 to Digoutdata
+    delay();      // pause
+   }     
+}
+
+void delay(void){            //delay function.
+    int j;                      //loop variable j
+    for (j=0; j<1000000; j++) {
+        j++;
+        j--;                      //waste time
+    }
+}
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