Added pulseIn API function

Author: rogerclarkmelbourne

STM32F1/cores/maple/stm32f1/wiring_pulse_f1.cpp

@@ -0,0 +1,75 @@
+#include <wiring_pulse.h>
+#include "boards.h"
+/* Measures the length (in microseconds) of a pulse on the pin; state is HIGH
+ * or LOW, the type of pulse to measure.  Works on pulses from 2-3 microseconds
+ * to 3 minutes in length, but must be called at least a few dozen microseconds
+ * before the start of the pulse. */
+ 
+ 
+ /*
+  * Roger Clark
+  *
+  * Note. The API spec for this function published on http://www.arduino.cc/en/Reference/PulseIn 
+  * doesn't reflect what either the AVR or SAM version of this function actualy do with regard to the timeout value
+  *
+  * "timeout (optional): the number of microseconds to wait for the pulse to start; default is one second (unsigned long) "
+  *
+  * Because the timeout, is actually coded as the total time to both wait while the input is in the state requested
+  * then wait for the opposite state duration
+  * then count the length of the pulse when it has the value of state (HIGH or LOW)
+  * 
+  * So I think the code for both the AVR and the Due is wrong in that it doesnt match the spec
+  * 
+  * I have done basically the same as the AVR and Due code, except to make the timeout a bit more accurate I have put in a dummy volatile varable 
+  * dummyWidth so that both the waiting while loops take the same number of clock cycles to execute as the acount width counting loop
+  *
+  * to be slighly more accurate the maxLoops variable really needs to take into account the loop setup code, but its probably as good as necessary
+  *
+  */
+uint32_t pulseIn( uint32_t pin, uint32_t state, uint32_t timeout )
+{
+   // cache the port and bit of the pin in order to speed up the
+   // pulse width measuring loop and achieve finer resolution.  calling
+   // digitalRead() instead yields much coarser resolution.
+ 
+	gpio_dev *dev=PIN_MAP[pin].gpio_device;
+	uint32_t bit = (1U << PIN_MAP[pin].gpio_bit);
+   
+
+   uint32_t width = 0; // keep initialization out of time critical area
+   
+   // convert the timeout from microseconds to a number of times through
+   // the initial loop; it takes 16 clock cycles per iteration.
+   uint32_t numloops = 0;
+   uint32_t maxloops =  timeout * ( F_CPU / 16000000);
+   volatile uint32_t dummyWidth=0;
+   
+   // wait for any previous pulse to end
+   while ( (dev->regs->IDR & bit)  == bit)   {
+      if (numloops++ == maxloops)  {
+         return 0;
+      }
+	   dummyWidth++;
+   }
+   
+   // wait for the pulse to start
+   while ((dev->regs->IDR & bit) != bit)   {
+      if (numloops++ == maxloops) {
+         return 0;
+      }
+	  dummyWidth++;
+   }
+   
+   // wait for the pulse to stop
+   while ((dev->regs->IDR & bit) == bit) {
+      if (numloops++ == maxloops)  {
+         return 0;
+      }
+      width++;
+   }
+
+   // Excluding time taking up by the interrupts, it needs 16 clock cycles to look through the last while loop  
+   // 5 is added as a fiddle factor to correct for interrupts etc. But ultimately this would only be accurate if it was done ona hardware timer
+   
+   return (uint32_t)( ( (unsigned long long)(width+5) *  (unsigned long long) 16000000.0) /(unsigned long long)F_CPU ) ;
+}

STM32F1/cores/maple/wiring_pulse.h

@@ -0,0 +1,37 @@
+/******************************************************************************
+ * The MIT License
+ *
+ * Copyright (c) 2015 Roger Clark
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy,
+ * modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *****************************************************************************/
+
+
+
+#ifndef _WIRISH_PULSE_H_
+#define _WIRISH_PULSE_H_
+
+#include <libmaple/gpio.h>
+
+uint32_t pulseIn( uint32_t ulPin, uint32_t ulState, uint32_t ulTimeout = 1000000L ) ;
+
+
+#endif

STM32F1/cores/maple/wirish.h

@@ -59,6 +59,7 @@
 #include <wirish_math.h>
 #include <wirish_time.h>
 #include <wirish_constants.h>
+#include <wiring_pulse.h>
 
 #if STM32_MCU_SERIES == STM32_SERIES_F1 /* FIXME [0.0.13?] port to F2 */
 //#include <HardwareSPI.h>