mirror of
https://github.com/RobTillaart/Arduino.git
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72 lines
1.8 KiB
C++
72 lines
1.8 KiB
C++
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//
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// FILE: AsyncAnalog.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.3
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// DATE: 2018-09-05
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// PURPOSE: async version of analogRead, prevent blocking wait
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//
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// backgrounder
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// https://www.avrfreaks.net/forum/tut-c-newbies-guide-avr-adc?name=PNphpBB2&file=viewtopic&t=56429
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//
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// HISTORY:
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// 0.1.0 2018-09-05 initial version, based upon analogRead()
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// 0.1.1 2020-03-26 minor refactor
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// 0.1.2 2020-05-27 update library.json
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// 0.1.3 2020-12-12 added Arduino CI, minor fixes
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#include "AsyncAnalog.h"
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#if defined(ARDUINO_ARCH_AVR)
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AsyncAnalog::AsyncAnalog(const uint8_t pin)
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{
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_pin = pin;
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#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
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if (_pin >= 54) _pin -= 54;
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#else
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if (_pin >= 14) _pin -= 14;
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#endif
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}
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void AsyncAnalog::start()
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{
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#if defined(ADCSRB) && defined(MUX5)
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// the MUX5 bit of ADCSRB selects whether we're reading from channels
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// 0 to 7 (MUX5 low) or 8 to 15 (MUX5 high).
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ADCSRB = (ADCSRB & ~(1 << MUX5)) | (((_pin >> 3) & 0x01) << MUX5);
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#endif
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#if defined(ADMUX)
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// set the analog reference (high two bits of ADMUX) and select the
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// channel (low 4 bits). this also sets ADLAR (left-adjust result)
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// to 0 (the default).
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ADMUX = (DEFAULT << 6) | (_pin & 0x07);
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#endif
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sbi(ADCSRA, ADSC);
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}
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bool AsyncAnalog::ready()
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{
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// ADSC is cleared when the conversion finishes
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return bit_is_set(ADCSRA, ADSC) == 0;
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}
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int AsyncAnalog::value()
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{
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// we have to read ADCL first; doing so locks both ADCL
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// and ADCH until ADCH is read. reading ADCL second would
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// cause the results of each conversion to be discarded,
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// as ADCL and ADCH would be locked when it completed.
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int low = ADCL;
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int high = ADCH;
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// combine the two bytes
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return (high << 8) | low;
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}
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#endif // ARDUINO_ARCH_AVR
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// -- END OF FILE --
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