measure cpu load

buttons.c

@@ -28,7 +28,6 @@ uint32_t gADCSamplingRate;      // [Hz] actual ADC sampling rate
 // imported globals
 extern uint32_t gSystemClock;   // [Hz] system clock frequency
 extern volatile uint32_t gTime; // time in hundredths of a second
-extern volatile uint8_t drawRequested;
 
 // initialize all button and joystick handling hardware
 void ButtonInit(void)

main.c

@@ -13,6 +13,7 @@
 #include "driverlib/fpu.h"
 #include "driverlib/sysctl.h"
 #include "driverlib/interrupt.h"
+#include "driverlib/timer.h"
 #include "Crystalfontz128x128_ST7735.h"
 #include <stdio.h>
 #include "grlib/grlib.h"
@@ -28,7 +29,7 @@
 
 uint32_t gSystemClock; // [Hz] system clock frequency
 volatile uint32_t gTime = 0; // time in hundredths of a second
-volatile uint8_t drawRequested = 1;
+volatile uint8_t refresh = 1;
 
 // assumming square lcd
 #define HEIGHT LCD_VERTICAL_MAX
@@ -48,6 +49,8 @@ const float gVoltageScale[VOLTAGE_SCALES] = {
     0.1, 0.2, 0.5, 1., 2.
 };
 
+uint32_t cputime_unloaded;
+
 int RisingTrigger(void);
 
 // start a pwm test signal
@@ -72,6 +75,26 @@ void start_signal() {
   PWMGenEnable(PWM0_BASE, PWM_GEN_1);
 }
 
+uint32_t cpu_load_count(void)
+{
+    uint32_t i = 0;
+    TimerIntClear(TIMER1_BASE, TIMER_TIMA_TIMEOUT);
+    TimerEnable(TIMER1_BASE, TIMER_A); // start one-shot timer
+    while (!(TimerIntStatus(TIMER1_BASE, false) & TIMER_TIMA_TIMEOUT))
+        i++;
+    return i;
+}
+
+void start_cputimer() {
+    // initialize timer 1 in one-shot mode for polled timing
+    SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER1);
+    TimerDisable(TIMER1_BASE, TIMER_BOTH);
+    TimerConfigure(TIMER1_BASE, TIMER_CFG_ONE_SHOT);
+    TimerLoadSet(TIMER1_BASE, TIMER_A, gSystemClock/100); // 10ms interval
+    // baseline load
+    cputime_unloaded = cpu_load_count();
+}
+
 int main(void) {
     IntMasterDisable();
 
@@ -93,24 +116,33 @@ int main(void) {
 
 #ifdef DISPLAY_TIME
     uint32_t time;  // local copy of gTime
-    char str[50];   // string buffer
 #endif // DISPLAY_TIME
+    char str[50];   // string buffer
     
     // full-screen rectangle
     tRectangle rectFullScreen = {0, 0, GrContextDpyWidthGet(&sContext)-1, GrContextDpyHeightGet(&sContext)-1};
 
     ButtonInit();
+
+    start_cputimer();
+
     IntMasterEnable();
 
     uint8_t voltage_scale = 0;
 
     while (true) {
+        // calculate cpu usage
+        uint32_t cputime_loaded;
+        cputime_loaded = cpu_load_count();
+        float usage_percent;
+        usage_percent = (1.0 - (float) cputime_loaded / (float) cputime_unloaded) * (float) 100.;
+
         // handle buttons
         Button button = (Button) 0;
         while (fifo_get(&button)) {
             switch (button) {
                 case S2: // draw
-                    drawRequested = 1;
+                    refresh = !refresh;
                     break;
                 case Up: // next scale
                     voltage_scale = (voltage_scale + 1) % VOLTAGE_SCALES;
@@ -124,7 +156,6 @@ int main(void) {
         GrContextForegroundSet(&sContext, ClrBlack);
         GrRectFill(&sContext, &rectFullScreen); // fill screen with black
 
-
         GrContextForegroundSet(&sContext, ClrBlue);
 
         // draw gridlines from the center out
@@ -138,24 +169,26 @@ int main(void) {
         }
 
 
+        // info
+        GrContextForegroundSet(&sContext, ClrWheat);
+        GrStringDraw(&sContext, gVoltageScaleStr[voltage_scale], /*length*/ -1, /*x*/ 0, /*y*/ 0, /*opaque*/ false);
+        snprintf(str, sizeof(str), "CPU Load %.1f%%", usage_percent); 
+        GrStringDraw(&sContext, str, /*length*/ -1, /*x*/ 0, /*y*/ HEIGHT - 10, /*opaque*/ false);
+
         // display graph
         #define LOCAL_BUF_LEN 128
         uint16_t local_adc_buffer[LOCAL_BUF_LEN]; // copy of adc buffer
         int32_t adc_current_index;
         int32_t j;
-        if (drawRequested) {
+        if (refresh) {
             int trigger = RisingTrigger();
 
             adc_current_index = trigger - (WIDTH / 2);
             for (j=0; j<LOCAL_BUF_LEN; j++) {
                 local_adc_buffer[j] = gADCBuffer[ADC_BUFFER_WRAP(adc_current_index + j)];
             }
-            drawRequested = 0;
         }
 
-        GrContextForegroundSet(&sContext, ClrWheat);
-        GrStringDraw(&sContext, gVoltageScaleStr[voltage_scale], /*length*/ -1, /*x*/ 0, /*y*/ 0, /*opaque*/ false);
-
         float fVoltsPerDiv = gVoltageScale[voltage_scale];
         float fScale = (VIN_RANGE * PIXELS_PER_DIV)/((1 << ADC_BITS) * fVoltsPerDiv);