ScanningModule.h

/*
MIT License
 
Copyright (c) 2018 Brian T. Park
 
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 ACE_SEGMENT_SCANNING_MODULE_H
#define ACE_SEGMENT_SCANNING_MODULE_H
 
#include <stdint.h>
#include <AceCommon.h> // incrementMod()
#include "../hw/ClockInterface.h" // ClockInterface
#include "../LedModule.h"
 
class ScanningModuleTest_displayCurrentField;
 
namespace ace_segment {
 
template <
    typename T_LM,
    uint8_t T_DIGITS,
    uint8_t T_SUBFIELDS = 1,
    typename T_CI = ClockInterface>
class ScanningModule : public LedModule {
 
  public:
    explicit ScanningModule(
        const T_LM& ledMatrix,
        uint8_t framesPerSecond
    ):
        LedModule(T_DIGITS),
        mLedMatrix(ledMatrix),
        mFramesPerSecond(framesPerSecond)
    {}
 
    void begin() {
      // Set up durations for the renderFieldWhenReady() polling function.
      mMicrosPerField = (uint32_t) 1000000UL / getFieldsPerSecond();
      mLastRenderFieldMicros = T_CI::micros();
 
      // Initialize variables needed for multiplexing.
      mCurrentDigit = 0;
      mPrevDigit = T_DIGITS - 1;
      mCurrentSubField = 0;
      mPattern = 0;
 
      // Set initial patterns and global brightness.
      mLedMatrix.clear();
      if (T_SUBFIELDS > 1) {
        setBrightness(T_SUBFIELDS / 2); // half brightness
      }
    }
 
 
    void end() {}
 
    //-----------------------------------------------------------------------
    // Implement the LedModule interface.
    //-----------------------------------------------------------------------
 
    uint8_t getNumDigits() const { return T_DIGITS; }
 
    void setPatternAt(uint8_t pos, uint8_t pattern) override {
      mPatterns[pos] = pattern;
    }
 
    uint8_t getPatternAt(uint8_t pos) override {
      return mPatterns[pos];
    }
 
    void setBrightness(uint8_t brightness) override {
      for (uint8_t i = 0; i < T_DIGITS; i++) {
        setBrightnessAt(i, brightness);
      }
    }
 
    //-----------------------------------------------------------------------
    // Additional brightness control. ScanningModule allows brightness to be
    // defined on a per-digit basis.
    //-----------------------------------------------------------------------
 
    void setBrightnessAt(uint8_t pos, uint8_t brightness) {
      if (pos >= T_DIGITS) return;
      mBrightnesses[pos] = (brightness >= T_SUBFIELDS)
          ? T_SUBFIELDS : brightness;
    }
 
    //-----------------------------------------------------------------------
    // Methods related to rendering.
    //-----------------------------------------------------------------------
 
    uint16_t getFramesPerSecond() const { return mFramesPerSecond; }
 
    uint16_t getFieldsPerSecond() const {
      return mFramesPerSecond * getFieldsPerFrame();
    }
 
    uint16_t getFieldsPerFrame() const { return T_DIGITS * T_SUBFIELDS; }
 
    uint16_t getMicrosPerField() const { return mMicrosPerField; }
 
    bool renderFieldWhenReady() {
      uint16_t now = T_CI::micros();
      uint16_t elapsedMicros = now - mLastRenderFieldMicros;
      if (elapsedMicros >= mMicrosPerField) {
        renderFieldNow();
        mLastRenderFieldMicros = now;
        return true;
      } else {
        return false;
      }
    }
 
    void renderFieldNow() {
      if (T_SUBFIELDS > 1) {
        displayCurrentFieldModulated();
      } else {
        displayCurrentFieldPlain();
      }
    }
 
  private:
    friend class ::ScanningModuleTest_displayCurrentField;
 
    // disable copy-constructor and assignment operator
    ScanningModule(const ScanningModule&) = delete;
    ScanningModule& operator=(const ScanningModule&) = delete;
 
    void displayCurrentFieldPlain() {
      const uint8_t pattern = mPatterns[mCurrentDigit];
      mLedMatrix.draw(mCurrentDigit, pattern);
      mPrevDigit = mCurrentDigit;
      ace_common::incrementMod(mCurrentDigit, T_DIGITS);
    }
 
    void displayCurrentFieldModulated() {
      // Calculate the maximum subfield duration for current digit.
      const uint8_t brightness = mBrightnesses[mCurrentDigit];
 
      // Implement pulse width modulation PWM, using the following boundaries:
      //
      // * If brightness == 0, then turn the digit OFF 100% of the time.
      // * If brightness >= T_SUBFIELDS, turn the digit ON 100% of the time.
      //
      // The mCurrentSubField is incremented modulo T_SUBFIELDS, so will always
      // be in the range of [0, T_SUBFIELDS-1]. The brightness will always be <=
      // T_SUBFIELDS, with the value of T_SUBFIELDS being 100% bright. So if we
      // turn on the LED when (mCurrentSubField < brightness), we get the
      // desired outcome.
      const uint8_t pattern = (mCurrentSubField < brightness)
          ? mPatterns[mCurrentDigit]
          : 0;
 
      if (pattern != mPattern || mCurrentDigit != mPrevDigit) {
        mLedMatrix.draw(mCurrentDigit, pattern);
        mPattern = pattern;
      }
 
      mCurrentSubField++;
      mPrevDigit = mCurrentDigit;
      if (mCurrentSubField >= T_SUBFIELDS) {
        ace_common::incrementMod(mCurrentDigit, T_DIGITS);
        mCurrentSubField = 0;
      }
    }
 
  private:
    // The ordering of the fields below partially motivated to save memory on
    // 32-bit processors.
 
    const T_LM& mLedMatrix;
 
    volatile uint8_t mPatterns[T_DIGITS];
 
    volatile uint8_t mBrightnesses[T_DIGITS];
 
    //-----------------------------------------------------------------------
    // Variables needed by renderFieldWhenReady() to render frames and fields at
    // a certain rate per second.
    //-----------------------------------------------------------------------
 
    uint16_t mMicrosPerField;
 
    uint16_t mLastRenderFieldMicros;
 
    uint8_t const mFramesPerSecond;
 
    //-----------------------------------------------------------------------
    // Variables needed to keep track of the multiplexing of the digits,
    // and PWM of a single digit.
    //-----------------------------------------------------------------------
 
    uint8_t mCurrentDigit;
 
    uint8_t mPrevDigit;
 
    uint8_t mCurrentSubField;
 
    uint8_t mPattern;
};
 
}
 
#endif