HAL_AVR: support set_stop_pin() and set_settle_time() for analogin

useful for dual sonar support

libraries/AP_HAL_AVR/AnalogIn.h

@@ -19,7 +19,8 @@ public:
     float read_latest();
     void set_pin(uint8_t p);
     float voltage_average();
-    
+    void set_stop_pin(uint8_t p);
+    void set_settle_time(uint16_t settle_time_ms);    
 
     /* implementation specific interface: */
 
@@ -30,6 +31,12 @@ public:
      * from interrupt */
     void setup_read();
 
+    /* stop_read(): called to stop device measurement */
+    void stop_read();
+
+    /* reading_settled(): called to check if we have read for long enough */
+    bool reading_settled();
+
     /* read_average: called to calculate and clear the internal average.
      * implements read_average(), unscaled. */
     float _read_average();
@@ -44,6 +51,13 @@ private:
 
     /* _pin designates the ADC input mux for the sample */
     uint8_t _pin;
+
+    /* _stop_pin designates a digital pin to use for
+       enabling/disabling the analog device */
+    uint8_t _stop_pin;
+    uint16_t _settle_time_ms;
+    uint32_t _read_start_time_ms;
+
     /* prescale scales the raw measurments for read()*/
     const float _prescale;
 };
@@ -64,7 +78,7 @@ protected:
     static ADCSource* _channels[AVR_INPUT_MAX_CHANNELS];
     static int16_t _num_channels;
     static int16_t _active_channel;
-    static int16_t _channel_repeat_count;
+    static uint16_t _channel_repeat_count;
 
 private:
     ADCSource _vcc;

libraries/AP_HAL_AVR/AnalogIn_ADC.cpp

@@ -1,3 +1,5 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+
 #include <AP_HAL.h>
 #if (CONFIG_HAL_BOARD == HAL_BOARD_APM1 || CONFIG_HAL_BOARD == HAL_BOARD_APM2)
 
@@ -11,6 +13,7 @@ extern const AP_HAL::HAL& hal;
 
 ADCSource::ADCSource(uint8_t pin, float prescale) :
     _pin(pin),
+    _stop_pin(ANALOG_INPUT_NONE),
     _sum_count(0),
     _sum(0),
     _prescale(prescale)
@@ -42,30 +45,39 @@ float ADCSource::read_latest() {
  */
 float ADCSource::voltage_average(void)
 {
-	float vcc_mV = hal.analogin->channel(ANALOG_INPUT_BOARD_VCC)->read_average();
-	float v = read_average();
-	// constrain Vcc reading so that a bad Vcc doesn't throw off
-	// the reading of other sources too badly
-	if (vcc_mV < 4000) {
-		vcc_mV = 4000;
-	} else if (vcc_mV > 6000) {
-		vcc_mV = 6000;
-	}
-	return v * vcc_mV * 9.765625e-7; // 9.765625e-7 = 1.0/(1024*1000)
+    float vcc_mV = hal.analogin->channel(ANALOG_INPUT_BOARD_VCC)->read_average();
+    float v = read_average();
+    // constrain Vcc reading so that a bad Vcc doesn't throw off
+    // the reading of other sources too badly
+    if (vcc_mV < 4000) {
+        vcc_mV = 4000;
+    } else if (vcc_mV > 6000) {
+        vcc_mV = 6000;
+    }
+    return v * vcc_mV * 9.765625e-7; // 9.765625e-7 = 1.0/(1024*1000)
 }
 
 void ADCSource::set_pin(uint8_t pin) {
     _pin = pin;
 }
 
+void ADCSource::set_stop_pin(uint8_t pin) {
+    _stop_pin = pin;
+}
+
+void ADCSource::set_settle_time(uint16_t settle_time_ms) 
+{
+    _settle_time_ms = settle_time_ms;
+}
+
 /* read_average is called from the normal thread (not an interrupt). */
 float ADCSource::_read_average() {
     uint16_t sum;
     uint8_t sum_count;
 
     if (_sum_count == 0) {
-	    // avoid blocking waiting for new samples
-	    return _last_average;
+        // avoid blocking waiting for new samples
+        return _last_average;
     }
 
     /* Read and clear in a critical section */
@@ -86,8 +98,16 @@ float ADCSource::_read_average() {
 }
 
 void ADCSource::setup_read() {
+    if (_stop_pin != ANALOG_INPUT_NONE) {
+        uint8_t digital_pin = hal.gpio->analogPinToDigitalPin(_stop_pin);
+        hal.gpio->pinMode(digital_pin, GPIO_OUTPUT);
+        hal.gpio->write(digital_pin, 1);
+    }
+    if (_settle_time_ms != 0) {
+        _read_start_time_ms = hal.scheduler->millis();
+    }
     if (_pin == ANALOG_INPUT_BOARD_VCC) {
-	ADCSRB = (ADCSRB & ~(1 << MUX5));
+        ADCSRB = (ADCSRB & ~(1 << MUX5));
         ADMUX = _BV(REFS0)|_BV(MUX4)|_BV(MUX3)|_BV(MUX2)|_BV(MUX1);
     } else if (_pin == ANALOG_INPUT_NONE) {
         /* noop */
@@ -97,6 +117,22 @@ void ADCSource::setup_read() {
     }
 }
 
+void ADCSource::stop_read() {
+    if (_stop_pin != ANALOG_INPUT_NONE) {
+        uint8_t digital_pin = hal.gpio->analogPinToDigitalPin(_stop_pin);
+        hal.gpio->pinMode(digital_pin, GPIO_OUTPUT);
+        hal.gpio->write(digital_pin, 0);
+    }
+}
+
+bool ADCSource::reading_settled() 
+{
+    if (_settle_time_ms != 0 && (hal.scheduler->millis() - _read_start_time_ms) < _settle_time_ms) {
+        return false;
+    }
+    return true;
+}
+
 /* new_sample is called from an interrupt. It always has access to
  *  _sum and _sum_count. Lock out the interrupts briefly with
  * cli/sei to read these variables from outside an interrupt. */

libraries/AP_HAL_AVR/AnalogIn_Common.cpp

@@ -1,3 +1,5 @@
+/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
+
 #include <AP_HAL.h>
 #if (CONFIG_HAL_BOARD == HAL_BOARD_APM1 || CONFIG_HAL_BOARD == HAL_BOARD_APM2)
 
@@ -18,7 +20,7 @@ extern const AP_HAL::HAL& hal;
 ADCSource* AVRAnalogIn::_channels[AVR_INPUT_MAX_CHANNELS] = {NULL};
 int16_t AVRAnalogIn::_num_channels = 0;
 int16_t AVRAnalogIn::_active_channel = 0;
-int16_t AVRAnalogIn::_channel_repeat_count = 0;
+uint16_t AVRAnalogIn::_channel_repeat_count = 0;
 
 AVRAnalogIn::AVRAnalogIn() :
     _vcc(ADCSource(ANALOG_INPUT_BOARD_VCC))
@@ -60,8 +62,8 @@ void AVRAnalogIn::_register_channel(ADCSource* ch) {
     }
 }
 
-void AVRAnalogIn::_timer_event(uint32_t t) {
-
+void AVRAnalogIn::_timer_event(uint32_t t) 
+{
     if (_channels[_active_channel]->_pin == ANALOG_INPUT_NONE) {
         _channels[_active_channel]->new_sample(0);
         goto next_channel;
@@ -79,14 +81,15 @@ void AVRAnalogIn::_timer_event(uint32_t t) {
     }
 
     _channel_repeat_count++;
-    if (_channel_repeat_count < CHANNEL_READ_REPEAT) {
+    if (_channel_repeat_count < CHANNEL_READ_REPEAT ||
+        !_channels[_active_channel]->reading_settled()) {
         /* Start a new conversion, throw away the current conversion */
         ADCSRA |= _BV(ADSC);
         return;
-    } else {
-        _channel_repeat_count = 0;
     }
 
+    _channel_repeat_count = 0;
+
     /* Read the conversion registers. */
     {
         uint8_t low = ADCL;
@@ -96,6 +99,8 @@ void AVRAnalogIn::_timer_event(uint32_t t) {
         _channels[_active_channel]->new_sample( sample );
     }
 next_channel:
+    /* stop the previous channel, if a stop pin is defined */
+    _channels[_active_channel]->stop_read();
     /* Move to the next channel */
     _active_channel = (_active_channel + 1) % _num_channels;
     /* Setup the next channel's conversion */