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AP_AnalogSource: allow for the 'NONE' pin in Arduino ADC

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This allows us to have a configuration parameter for a pin which
defaults to -1, meaning not to read a pin at all. It will always
return 0
This commit is contained in:
Andrew Tridgell 2012-11-06 21:45:40 +11:00
parent 736cb4c34b
commit 403721f8ca
2 changed files with 25 additions and 9 deletions
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31
libraries/AP_AnalogSource/AP_AnalogSource_Arduino.cpp
View File

@ -27,6 +27,10 @@ static volatile struct {
// each conversion takes about 125 microseconds
static void adc_timer(uint32_t t)
{
if (pins[next_pin_index].pin == ANALOG_PIN_NONE) {
goto next_pin;
}
if (bit_is_set(ADCSRA, ADSC) || num_pins_watched == 0) {
// conversion is still running. This should be
// very rare, as we are called at 1kHz
@ -42,9 +46,11 @@ static void adc_timer(uint32_t t)
}
// remember the value we got
uint8_t low = ADCL;
uint8_t high = ADCH;
pins[next_pin_index].output = low | (high<<8);
{
uint8_t low = ADCL;
uint8_t high = ADCH;
pins[next_pin_index].output = low | (high<<8);
}
pins[next_pin_index].sum += pins[next_pin_index].output;
if (pins[next_pin_index].sum_count >= 63) {
// we risk overflowing the 16 bit sum
@ -54,23 +60,32 @@ static void adc_timer(uint32_t t)
pins[next_pin_index].sum_count++;
}
next_pin:
next_pin_count = 0;
if (num_pins_watched != 0) {
next_pin_index = (next_pin_index+1) % num_pins_watched;
}
uint8_t pin = pins[next_pin_index].pin;
if (pin == ANALOG_PIN_VCC) {
if (pin == ANALOG_PIN_NONE) {
// setup for returning 0
pins[next_pin_index].output = 0;
pins[next_pin_index].sum = 0;
pins[next_pin_index].sum_count = 1;
} else if (pin == ANALOG_PIN_VCC) {
// we're reading the board voltage
ADMUX = _BV(REFS0)|_BV(MUX4)|_BV(MUX3)|_BV(MUX2)|_BV(MUX1);
// start the next conversion
ADCSRA |= _BV(ADSC);
} else {
// we're reading an external pin
ADCSRB = (ADCSRB & ~(1 << MUX5)) | (((pin >> 3) & 0x01) << MUX5);
ADMUX = _BV(REFS0) | (pin & 0x07);
}
// start the next conversion
ADCSRA |= _BV(ADSC);
// start the next conversion
ADCSRA |= _BV(ADSC);
}
}
// setup the timer process. This must be called before any analog
@ -134,7 +149,7 @@ float AP_AnalogSource_Arduino::read(void)
// remap pin numbers to physical pin
uint8_t AP_AnalogSource_Arduino::_remap_pin(uint8_t pin)
{
if (pin != ANALOG_PIN_VCC) {
if (pin != ANALOG_PIN_VCC && pin != ANALOG_PIN_NONE) {
// allow pin to be a channel (i.e. "A0") or an actual pin
#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
if (pin >= 54) pin -= 54;

3
libraries/AP_AnalogSource/AP_AnalogSource_Arduino.h
View File

@ -8,7 +8,8 @@
// special pin number which is interpreted as a
// internal Vcc voltage read
#define ANALOG_PIN_VCC 255
#define ANALOG_PIN_VCC 254
#define ANALOG_PIN_NONE 255
class AP_AnalogSource_Arduino : public AP_AnalogSource
{