AP_ADC: rework ADC library to use PeriodicProcess and ISR_Register

this makes it possible to build the ADC library when another driver
may also want that interrupt

libraries/AP_ADC/AP_ADC.h

@@ -2,6 +2,8 @@
 #define AP_ADC_H
 
 #include <stdint.h>
+#include <stdlib.h>
+#include <../AP_PeriodicProcess/AP_PeriodicProcess.h>
 
 /*
 	AP_ADC.cpp - Analog Digital Converter Base Class for Ardupilot Mega
@@ -22,7 +24,7 @@ class AP_ADC
 {
   public:
 	AP_ADC() {};  // Constructor
-	virtual void Init() {};
+	virtual void Init(AP_PeriodicProcess * scheduler = NULL) = 0;
 
 	/* read one channel value */
 	virtual uint16_t Ch(uint8_t ch_num) = 0;

libraries/AP_ADC/AP_ADC_ADS7844.cpp

@@ -83,10 +83,9 @@ static inline unsigned char ADC_SPI_transfer(unsigned char data)
 }
 
 
-ISR (TIMER2_OVF_vect)
+void AP_ADC_ADS7844::read(void)
 {
 	uint8_t ch;
-	static uint8_t timer_offset;
 
 	bit_clear(PORTC, 4);							// Enable Chip Select (PIN PC4)
 	ADC_SPI_transfer(adc_cmd[0]);						// Command to read the first channel
@@ -119,10 +118,6 @@ ISR (TIMER2_OVF_vect)
 
 	bit_set(PORTC, 4);					// Disable Chip Select (PIN PC4)
 
-	// this gives us a sample rate between 781Hz and 1302Hz. We
-	// randomise it to try to minimise aliasing effects
-        timer_offset = (timer_offset + 49) % 32;
-        TCNT2 = TCNT2_781_HZ + timer_offset;
 }
 
 
@@ -134,7 +129,7 @@ AP_ADC_ADS7844::AP_ADC_ADS7844() :
 }
 
 // Public Methods //////////////////////////////////////////////////////////////
-void AP_ADC_ADS7844::Init(void)
+void AP_ADC_ADS7844::Init( AP_PeriodicProcess * scheduler )
 {
 	pinMode(ADC_CHIP_SELECT, OUTPUT);
 
@@ -162,13 +157,8 @@ void AP_ADC_ADS7844::Init(void)
 
 	last_ch6_micros = micros();
 
-	// Enable Timer2 Overflow interrupt to capture ADC data
-	TIMSK2 = 0;			// Disable interrupts
-	TCCR2A = 0;			// normal counting mode
-	TCCR2B = _BV(CS21) | _BV(CS22);	// Set prescaler of clk/256
-	TCNT2	= 0;
-	TIFR2	= _BV(TOV2);	   // clear pending interrupts;
-	TIMSK2 = _BV(TOIE2);	   // enable the overflow interrupt
+    scheduler->register_process( AP_ADC_ADS7844::read );
+
 }
 
 // Read one channel value

libraries/AP_ADC/AP_ADC_ADS7844.h

@@ -14,13 +14,14 @@
 #define ADC_ACCEL_FILTER_SIZE 8
 
 #include "AP_ADC.h"
+#include "../AP_PeriodicProcess/AP_PeriodicProcess.h"
 #include <inttypes.h>
 
 class AP_ADC_ADS7844 : public AP_ADC
 {
 	public:
 	AP_ADC_ADS7844();  // Constructor
-	void 	Init();
+	void Init( AP_PeriodicProcess * scheduler );
 
 	// Read 1 sensor value
 	uint16_t Ch(unsigned char ch_num);
@@ -34,6 +35,7 @@ class AP_ADC_ADS7844 : public AP_ADC
 	uint16_t 		_prev_gyro[3];
 	uint16_t 		_prev_accel[3];
 	uint8_t			_filter_index_accel;
+	static void read( void );
 
 };
 

libraries/AP_ADC/AP_ADC_HIL.cpp

@@ -39,7 +39,7 @@ AP_ADC_HIL::AP_ADC_HIL()
 	last_hil_time = millis();
 }
 
-void AP_ADC_HIL::Init(void)
+void AP_ADC_HIL::Init( AP_PeriodicProcess * scheduler )
 {
 }
 

libraries/AP_ADC/AP_ADC_HIL.h

@@ -28,7 +28,7 @@ class AP_ADC_HIL : public AP_ADC
 
 	///
 	// Initializes sensor, part of public AP_ADC interface
-	void Init();
+	void Init(AP_PeriodicProcess*);
 
 	///
 	// Read the sensor, part of public AP_ADC interface

libraries/AP_ADC/examples/AP_ADC_test/AP_ADC_test.pde

@@ -5,10 +5,16 @@
 */
 
 #include <FastSerial.h>
+#include <Arduino_Mega_ISR_Registry.h>
+#include <AP_PeriodicProcess.h>
 #include <AP_ADC.h> // ArduPilot Mega ADC Library
 
 FastSerialPort0(Serial);        // FTDI/console
 
+Arduino_Mega_ISR_Registry isr_registry;
+AP_TimerAperiodicProcess  adc_scheduler;
+
+
 unsigned long timer;
 AP_ADC_ADS7844 adc;
 
@@ -17,7 +23,11 @@ void setup()
 	Serial.begin(115200, 128, 128);
 	Serial.println("ArduPilot Mega ADC library test");
 	delay(1000);
-	adc.Init();   // APM ADC initialization
+
+    isr_registry.init();
+    adc_scheduler.init(&isr_registry);
+
+	adc.Init(&adc_scheduler);   // APM ADC initialization
 	delay(1000);
 	timer = millis();
 }

libraries/AP_ADC/examples/AP_ADC_test/Makefile

@@ -1,2 +1,2 @@
-BOARD	=	mega
+BOARD	=	mega2560
 include ../../../AP_Common/Arduino.mk