main.c

@@ -90,6 +90,20 @@ const float gVoltageScale[VOLTAGE_SCALES] = {
     0.1, 0.2, 0.5, 1., 2.
 };
 
+#define TIME_SCALES 6
+const char * const gTimeScaleStr[TIME_SCALES] = {
+"100 ms", "50 ms", "20 ms", " 10 ms", "50 us", "20 us"
+};
+
+const uint64_t gTImeScale[TIME_SCALES] = {
+    100 * 1000 / PIXELS_PER_DIV,
+    50 * 1000 / PIXELS_PER_DIV,
+    20 * 1000 / PIXELS_PER_DIV,
+    10 * 1000 / PIXELS_PER_DIV,
+    50 / PIXELS_PER_DIV,
+    20 / PIXELS_PER_DIV,
+};
+
 int Trigger(bool rising);
 
 // start a pwm test signal
@@ -269,6 +283,14 @@ void handle_user_input() {
             case Down: // previous scale
                 local_options.voltage_scale = (local_options.voltage_scale + VOLTAGE_SCALES - 1) % VOLTAGE_SCALES;
                 break;
+            case Right: // next scale
+                local_options.time_scale = (local_options.time_scale + 1) % TIME_SCALES;
+                set_frequency(gTImeScale[local_options.time_scale]);
+                break;
+            case Left: // previous scale
+                local_options.time_scale = (local_options.time_scale + TIME_SCALES - 1) % TIME_SCALES;
+                set_frequency(gTImeScale[local_options.time_scale]);
+                break;
         }
 
         Semaphore_pend(options_sem, BIOS_WAIT_FOREVER);
@@ -313,31 +335,23 @@ void display_waveform(UArg arg1, UArg arg2)
 
         // info
         GrContextForegroundSet(&sContext, ClrWheat);
-
+        GrStringDraw(&sContext, gVoltageScaleStr[local_options.voltage_scale], /*length*/ -1, /*x*/ 0, /*y*/ 0, /*opaque*/ false);
+        GrStringDraw(&sContext, gTimeScaleStr[local_options.time_scale], /*length*/ -1, /*x*/ 60, /*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);
 
-
+        switch (local_options.trigger_mode) {
-        if (local_options.fft) {
+            case 1:
-            GrStringDraw(&sContext, "20 dB" , /*length*/ -1, /*x*/ 0, /*y*/ 0, /*opaque*/ false);
+                GrStringDraw(&sContext, "^", /*length*/ -1, /*x*/ WIDTH - 10, /*y*/ 0, /*opaque*/ false);
-
+                break;
-        } else {
+            case 0:
-            GrStringDraw(&sContext, gVoltageScaleStr[local_options.voltage_scale], /*length*/ -1, /*x*/ 0, /*y*/ 0, /*opaque*/ false);
+                GrStringDraw(&sContext, "v", /*length*/ -1, /*x*/ WIDTH - 10, /*y*/ 0, /*opaque*/ false);
-
+                break;
-            switch (local_options.trigger_mode) {
+            case 2:
-                case 1:
+                GrStringDraw(&sContext, "-", /*length*/ -1, /*x*/ WIDTH - 10, /*y*/ 0, /*opaque*/ false);
-                    GrStringDraw(&sContext, "^", /*length*/ -1, /*x*/ WIDTH - 10, /*y*/ 0, /*opaque*/ false);
+                break;
-                    break;
-                case 0:
-                    GrStringDraw(&sContext, "v", /*length*/ -1, /*x*/ WIDTH - 10, /*y*/ 0, /*opaque*/ false);
-                    break;
-                case 2:
-                    GrStringDraw(&sContext, "-", /*length*/ -1, /*x*/ WIDTH - 10, /*y*/ 0, /*opaque*/ false);
-                    break;
-          }
         }
 
-
         // display graph
         GrContextForegroundSet(&sContext, ClrYellow);
         int j;

sampling.c

@@ -119,6 +119,8 @@ void start_sampler() {
     SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
     SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC1);
 
+    // timer for low-speed
+    SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER2);
     // ADC clock
     uint32_t pll_frequency = SysCtlFrequencyGet(CRYSTAL_FREQUENCY);
     uint32_t pll_divisor =
@@ -143,3 +145,25 @@ void start_sampler() {
     ADCSequenceDMAEnable(ADC1_BASE, 0); // enable DMA for ADC1 sequence 0
     ADCIntEnableEx(ADC1_BASE, ADC_INT_DMA_SS0); // enable ADC1 sequence 0 DMA interrupt
 }
+
+void set_frequency(uint64_t microseconds) {
+    if (microseconds == 1) {
+        ADCSequenceDisable(ADC1_BASE, 0);
+        // don't use a timer for high speed
+        ADCSequenceConfigure(ADC1_BASE, 0, ADC_TRIGGER_ALWAYS, 0);
+        ADCSequenceEnable(ADC1_BASE, 0);
+        return;
+    }
+
+    // initialize timer 2 in periodic mode
+    TimerDisable(TIMER2_BASE, TIMER_BOTH);
+    TimerConfigure(TIMER2_BASE, TIMER_CFG_PERIODIC);
+    #define MICROSECONDS_PER_SECOND 1000000
+    TimerLoadSet(TIMER2_BASE, TIMER_A, (uint32_t) ((uint64_t) gSystemClock * microseconds / MICROSECONDS_PER_SECOND) - 1);
+    TimerControlTrigger(TIMER2_BASE, TIMER_A, true);
+    TimerEnable(TIMER2_BASE, TIMER_A);
+
+    ADCSequenceDisable(ADC1_BASE, 0);
+    ADCSequenceConfigure(ADC1_BASE, 0, ADC_TRIGGER_TIMER, 0);
+    ADCSequenceEnable(ADC1_BASE, 0);
+}