create sampling.c

main.c

@@ -26,28 +26,34 @@
 uint32_t gSystemClock; // [Hz] system clock frequency
 volatile uint32_t gTime = 0; // time in hundredths of a second
 
-int main(void)
+// start a pwm test signal
-{
+void start_signal() {
+  // configure M0PWM2, at GPIO PF2, BoosterPack 1 header C1 pin 2
+  SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
+  GPIOPinTypePWM(GPIO_PORTF_BASE, GPIO_PIN_2);
+  GPIOPinConfigure(GPIO_PF2_M0PWM2);
+  GPIOPadConfigSet(GPIO_PORTF_BASE, GPIO_PIN_2, GPIO_STRENGTH_2MA,
+                   GPIO_PIN_TYPE_STD);
+  // configure the PWM0 peripheral, gen 1, outputs 2 and 3
+  SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);
+  // use system clock without division
+  PWMClockSet(PWM0_BASE, PWM_SYSCLK_DIV_1);
+  PWMGenConfigure(PWM0_BASE, PWM_GEN_1,
+                  PWM_GEN_MODE_DOWN | PWM_GEN_MODE_NO_SYNC);
+  PWMGenPeriodSet(PWM0_BASE, PWM_GEN_1,
+                  roundf((float)gSystemClock / PWM_FREQUENCY));
+  PWMPulseWidthSet(PWM0_BASE, PWM_OUT_2,
+                   roundf((float)gSystemClock / PWM_FREQUENCY * 0.4f));
+  PWMOutputState(PWM0_BASE, PWM_OUT_2_BIT, true);
+  PWMGenEnable(PWM0_BASE, PWM_GEN_1);
+}
+
+int main(void) {
     IntMasterDisable();
 
-    // configure M0PWM2, at GPIO PF2, BoosterPack 1 header C1 pin 2
+    start_signal();
-    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
-    GPIOPinTypePWM(GPIO_PORTF_BASE, GPIO_PIN_2);
-    GPIOPinConfigure(GPIO_PF2_M0PWM2);
-    GPIOPadConfigSet(GPIO_PORTF_BASE, GPIO_PIN_2,
-    GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD);
-    // configure the PWM0 peripheral, gen 1, outputs 2 and 3
-    SysCtlPeripheralEnable(SYSCTL_PERIPH_PWM0);
-    // use system clock without division
-    PWMClockSet(PWM0_BASE, PWM_SYSCLK_DIV_1);
-    PWMGenConfigure(PWM0_BASE, PWM_GEN_1,
-    PWM_GEN_MODE_DOWN | PWM_GEN_MODE_NO_SYNC);
-    PWMGenPeriodSet(PWM0_BASE, PWM_GEN_1, roundf((float)gSystemClock/PWM_FREQUENCY));
-    PWMPulseWidthSet(PWM0_BASE, PWM_OUT_2,
-    roundf((float)gSystemClock/PWM_FREQUENCY*0.4f));
-    PWMOutputState(PWM0_BASE, PWM_OUT_2_BIT, true);
-    PWMGenEnable(PWM0_BASE, PWM_GEN_1);
 
+    start_sampler();
 
     // Enable the Floating Point Unit, and permit ISRs to use it
     FPUEnable();
@@ -103,4 +109,4 @@ int main(void)
 
         GrFlush(&sContext); // flush the frame buffer to the LCD
     }
-}
+}

sampling.c

@@ -0,0 +1,60 @@
+#include <stdint.h>
+#include <stdbool.h>
+#include "inc/tm4c1294ncpdt.h"
+#include "driverlib/adc.h"
+#include "sysctl_pll.h"
+
+
+#define ADC_BUFFER_SIZE 2048 // size must be a power of 2
+// index wrapping macro
+#define ADC_BUFFER_WRAP(i) ((i) & (ADC_BUFFER_SIZE - 1))
+// latest sample index
+volatile int32_t gADCBufferIndex = ADC_BUFFER_SIZE - 1;
+volatile uint16_t gADCBuffer[ADC_BUFFER_SIZE]; // circular buffer
+volatile uint32_t gADCErrors = 0; // number of missed ADC deadlines
+void ADC_ISR(void)
+{
+    // clear ADC1 sequence0 interrupt flag in the ADCISC register
+    <...>;
+    // check for ADC FIFO overflow
+    if(ADC1_OSTAT_R & ADC_OSTAT_OV0) {
+    gADCErrors++; // count errors
+    ADC1_OSTAT_R = ADC_OSTAT_OV0; // clear overflow condition
+    }
+    gADCBufferIndex = ADC_BUFFER_WRAP(gADCBufferIndex + 1)
+    // read sample from the ADC1 sequence 0 FIFO
+    gADCBuffer[gADCBufferIndex] = <...>;
+}
+
+
+void start_sampler() {
+    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
+    GPIOPinTypeADC(GPIO_PORTE_BASE,
+                    GPIO_PIN_0); // GPIO setup for analog input AIN3
+    // initialize ADC peripherals
+    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
+    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC1);
+    // ADC clock
+    uint32_t pll_frequency = SysCtlFrequencyGet(CRYSTAL_FREQUENCY);
+    uint32_t pll_divisor =
+        (pll_frequency - 1) / (16 * ADC_SAMPLING_RATE) + 1; // round up
+    ADCClockConfigSet(ADC0_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_FULL,
+                    pll_divisor);
+    ADCClockConfigSet(ADC1_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_FULL,
+                    pll_divisor);
+    // choose ADC1 sequence 0; disable before configuring
+    ADCSequenceDisable(ADC1_BASE, 0);
+    ADCSequenceConfigure(ADC1_BASE, 0, ADC_TRIGGER_ALWAYS,
+                        0); // specify the "Always" trigger
+    // in the 0th step, sample channel 3 (AIN3)
+    // enable interrupt, and make it the end of sequence
+    ADCSequenceStepConfigure(ADC1_BASE, 0, 0, ADC_CTL_CH3));
+    // enable the sequence. it is now sampling
+    ADCSequenceEnable(ADC0_BASE, 0);
+    // enable sequence 0 interrupt in the ADC1 peripheral
+    ADCIntEnable(INT_ADC1SS0);
+    IntPrioritySet(INT_ADC1SS0, 0); // set ADC1 sequence 0 interrupt priority
+    // enable ADC1 sequence 0 interrupt in int. controller
+    IntEnable(INT_ADC1SS0);
+
+}

tm4c1294ncpdt_startup_ccs.c

@@ -34,6 +34,7 @@ static void NmiSR(void);
 static void FaultISR(void);
 static void IntDefaultHandler(void);
 void ButtonISR(void);
+void ADC_ISR(void);
 
 //*****************************************************************************
 //
@@ -99,7 +100,7 @@ void (* const g_pfnVectors[])(void) =
     IntDefaultHandler,                      // PWM Generator 1
     IntDefaultHandler,                      // PWM Generator 2
     IntDefaultHandler,                      // Quadrature Encoder 0
-    IntDefaultHandler,                      // ADC Sequence 0
+    ADC_ISR,                      // ADC Sequence 0
     IntDefaultHandler,                      // ADC Sequence 1
     IntDefaultHandler,                      // ADC Sequence 2
     IntDefaultHandler,                      // ADC Sequence 3