Added Timer 'Input Capture' support and example

STM32F1/cores/maple/libmaple/timer.c

@@ -39,6 +39,7 @@ static void disable_channel(timer_dev *dev, uint8 channel);
 static void pwm_mode(timer_dev *dev, uint8 channel);
 static void output_compare_mode(timer_dev *dev, uint8 channel);
 static void encoder_mode(timer_dev *dev, uint8 channel) ;//CARLOS
+static void input_capture_mode(timer_dev *dev, uint8 channel);//@Cesco
 
 
 static inline void enable_irq(timer_dev *dev, timer_interrupt_id iid);
@@ -236,6 +237,9 @@ void timer_set_mode(timer_dev *dev, uint8 channel, timer_mode mode) {
     case TIMER_ENCODER: 
         encoder_mode(dev, channel); //find a way to pass all the needed stuff on the 8bit var
         break;
+    case TIMER_INPUT_CAPTURE:// code from @Cesco
+        input_capture_mode(dev, channel);
+        break;		
     }
 }
 
@@ -349,7 +353,11 @@ static void encoder_mode(timer_dev *dev, uint8 channel __attribute__((unused)))
     timer_resume(dev);
 }
 
-
+// Code supplied by @Cesco (on the forum) 
+static void input_capture_mode(timer_dev *dev, uint8 channel) {
+    timer_oc_set_mode(dev, channel, 0, TIMER_CCMR_CCS_INPUT_TI1);
+    timer_cc_enable(dev, channel);
+}
 
 static void enable_adv_irq(timer_dev *dev, timer_interrupt_id id);
 static void enable_bas_gen_irq(timer_dev *dev);

STM32F1/libraries/A_STM32_Examples/examples/Sensors/HardwareTimerInputCapture/HardwareTimerInputCapture.ino

@@ -0,0 +1,68 @@
+/* Example of the Timer Input Capture mode
+ *  
+ * Thanks to @cesco on the stm32duino.com
+ * 
+ * This example uses Timer2. Other timers also support this mode, bnt on the F103C 
+ * only Timer 2 has usable external trigger pins. PA0 and PA15
+ * Because the only other usable pin on the F103C is one of the USB pins.
+ * 
+ * Upload to your favourite F103Cx 
+ * Open the Serial plotter
+ * Put your finger on either PA0 or PA15 (depenidng whether you USE the pin remapping)
+ * 
+ * Observe your local mains frequency in terms of pulse width time.
+ *
+ */
+
+/* Timer2 external trigger  can be ether PA0 or PA15. 
+ To use use afio_remap(FIO_REMAP_TIM2_PARTIAL_1)  or afio_remap(AFIO_REMAP_TIM2_FULL)
+ Note. using afio_remap also changes the pins used by Timer2 CH1,CH2,CH3 amd CH4 
+ * See page 184 of the STM32F10x Refernce manual (PDF downloadable from ST.com
+ */
+
+//#define USE_REMAP_PIN
+#ifdef USE_REMAP_PIN
+const int timer2ExternalTriggerPin = PA15;
+#else
+const int timer2ExternalTriggerPin = PA0;
+#endif
+
+volatile boolean hasCapture;
+volatile uint16_t captureValue;
+volatile uint16_t lastCaptureValue=0;
+volatile uint16_t captureDifference=0;
+
+void captureCallback(void) {
+
+   hasCapture=true;
+   captureValue = Timer2.getCompare(1);
+   captureDifference = captureValue-lastCaptureValue;
+   lastCaptureValue=captureValue;   
+}
+
+void setup() {
+  
+  pinMode(timer2ExternalTriggerPin,INPUT);
+
+  #ifdef USE_REMAP_PIN
+    afio_remap(AFIO_REMAP_TIM2_PARTIAL_1);
+  #endif
+  
+  hasCapture = false;
+
+  Timer2.setPrescaleFactor(72); // prescaler to count 72,000,000 / 72 counts per second. i.e count microseconds
+  Timer2.setMode(TIMER_CH1, TIMER_INPUT_CAPTURE);
+  Timer2.attachCompare1Interrupt(captureCallback);
+
+}
+
+void loop()  {
+
+  // Printing inside the callback is not a good idea. 
+  // Hence the capture callback sets a flag , which is detected here
+  if (hasCapture)
+  {
+    Serial.println(captureDifference);
+    hasCapture=false;
+  }  
+}

STM32F1/system/libmaple/include/libmaple/timer.h

@@ -564,13 +564,15 @@ typedef enum timer_mode {
      * values, the corresponding interrupt is fired. */
     TIMER_OUTPUT_COMPARE,
 
-    /* TIMER_INPUT_CAPTURE, TODO: In this mode, the timer can measure the
+
+    /* TIMER_INPUT_CAPTURE, UNDER DEVELOPMENT: In this mode, the timer can measure the
      *                            pulse lengths of input signals */
     /* TIMER_ONE_PULSE, TODO: In this mode, the timer can generate a single
      *                        pulse on a GPIO pin for a specified amount of
      *                        time. */
      
      TIMER_ENCODER,  //CARLOS Change
+	 TIMER_INPUT_CAPTURE,// code from @cesco
 } timer_mode;
 
 /** Timer channel numbers */

STM32F1/system/libmaple/stm32f1/include/series/gpio.h

@@ -351,7 +351,8 @@ typedef enum afio_remap_peripheral {
      * Timer 2 partial remapping 2 (CH1 and ETR on PA0, CH2 on PA1,
      * CH3 on                                      PB10, CH4 on PB11) */
     AFIO_REMAP_TIM2_PARTIAL_2 = AFIO_MAPR_TIM2_REMAP_PA0_PA1_PB10_PB11,
-    /** Timer 2 full remapping */
+    /** Timer 2 full remapping 
+	(CH1/ETR/PA15, CH2/PB3, CH3/PB10, CH4/PB11) */
     AFIO_REMAP_TIM2_FULL      = AFIO_MAPR_TIM2_REMAP_FULL,
      /** USART 3 part remapping */
     AFIO_REMAP_USART3_PARTIAL = AFIO_MAPR_USART3_REMAP_PARTIAL,