Final version of ADC.c

Labware/Lab14_MeasurementOfDistance/ADC.c

-// ADC.c
-// Runs on LM4F120/TM4C123
-// Provide functions that initialize ADC0 SS3 to be triggered by
-// software and trigger a conversion, wait for it to finish,
-// and return the result. 
-// Daniel Valvano
-// January 15, 2016
-
-/* This example accompanies the book
-   "Embedded Systems: Introduction to ARM Cortex M Microcontrollers",
-   ISBN: 978-1469998749, Jonathan Valvano, copyright (c) 2015
-
- Copyright 2016 by Jonathan W. Valvano, valvano@mail.utexas.edu
-    You may use, edit, run or distribute this file
-    as long as the above copyright notice remains
- THIS SOFTWARE IS PROVIDED "AS IS".  NO WARRANTIES, WHETHER EXPRESS, IMPLIED
- OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF
- MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE.
- VALVANO SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL,
- OR CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
- For more information about my classes, my research, and my books, see
- http://users.ece.utexas.edu/~valvano/
- */
-
-#include "ADC.h"
-#include "..//tm4c123gh6pm.h"
-
-// This initialization function sets up the ADC 
-// Max sample rate: <=125,000 samples/second
-// SS3 triggering event: software trigger
-// SS3 1st sample source:  channel 1
-// SS3 interrupts: enabled but not promoted to controller
-void ADC0_Init(void){ 
-  
-}
-
-
-//------------ADC0_In------------
-// Busy-wait Analog to digital conversion
-// Input: none
-// Output: 12-bit result of ADC conversion
-unsigned long ADC0_In(void){  
-  return 0; // replace this line with proper code
-}
+// ADC.c
+// Runs on LM4F120/TM4C123
+// Provide functions that initialize ADC0 SS3 to be triggered by
+// software and trigger a conversion, wait for it to finish,
+// and return the result. 
+// Daniel Valvano
+// January 15, 2016
+
+/* This example accompanies the book
+   "Embedded Systems: Introduction to ARM Cortex M Microcontrollers",
+   ISBN: 978-1469998749, Jonathan Valvano, copyright (c) 2015
+
+ Copyright 2016 by Jonathan W. Valvano, valvano@mail.utexas.edu
+    You may use, edit, run or distribute this file
+    as long as the above copyright notice remains
+ THIS SOFTWARE IS PROVIDED "AS IS".  NO WARRANTIES, WHETHER EXPRESS, IMPLIED
+ OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF
+ MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE.
+ VALVANO SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL,
+ OR CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
+ For more information about my classes, my research, and my books, see
+ http://users.ece.utexas.edu/~valvano/
+ */
+
+#include "ADC.h"
+#include "..//tm4c123gh6pm.h"
+
+// This initialization function sets up the ADC 
+// Max sample rate: <=125,000 samples/second
+// SS3 triggering event: software trigger
+// SS3 1st sample source:  channel 1
+// SS3 interrupts: enabled but not promoted to controller
+void ADC0_Init(void){ 
+	   volatile unsigned long delay;
+  SYSCTL_RCGC2_R |= 0x00000010;   // 1) activate clock for Port E
+  delay = SYSCTL_RCGC2_R;         //    allow time for clock to stabilize
+  GPIO_PORTE_DIR_R &= ~0x04;      // 2) make PE2 input
+  GPIO_PORTE_AFSEL_R |= 0x04;     // 3) enable alternate function on PE2
+  GPIO_PORTE_DEN_R &= ~0x04;      // 4) disable digital I/O on PE2
+  GPIO_PORTE_AMSEL_R |= 0x04;     // 5) enable analog function on PE2
+  SYSCTL_RCGC0_R |= 0x00010000;   // 6) activate ADC0
+  delay = SYSCTL_RCGC2_R;        
+  SYSCTL_RCGC0_R &= ~0x00000300;  // 7) configure for 125K
+  ADC0_SSPRI_R = 0x0123;          // 8) Sequencer 3 is highest priority
+  ADC0_ACTSS_R &= ~0x0008;        // 9) disable sample sequencer 3
+  ADC0_EMUX_R &= ~0xF000;         // 10) seq3 is software trigger
+  ADC0_SSMUX3_R &= ~0x000F;       // 11) clear SS3 field
+  ADC0_SSMUX3_R += 1;             //    set channel Ain1 (PE2)
+  ADC0_SSCTL3_R = 0x0006;         // 12) no TS0 D0, yes IE0 END0
+  ADC0_ACTSS_R |= 0x0008;         // 13) enable sample sequencer 3
+}
+
+
+//------------ADC0_In------------
+// Busy-wait Analog to digital conversion
+// Input: none
+// Output: 12-bit result of ADC conversion
+unsigned long ADC0_In(void){  
+  unsigned long result;
+  ADC0_PSSI_R = 0x0008;            // 1) initiate SS3
+  while((ADC0_RIS_R&0x08)==0){};   // 2) wait for conversion done
+	result = ADC0_SSFIFO3_R&0xFFF;   // 3) read result
+	ADC0_ISC_R = 0x0008;             // 4) acknowledge completion
+  return result;
+}