rc_ppm.cpp

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/*
 * Copyright (c) 2017, James Jackson
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * * Neither the name of the copyright holder nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "rc_ppm.h"

RC_PPM* RC_PPM_Ptr = NULL;

void RC_PPM::init(const pwm_hardware_struct_t* conf)
{
  // Initialize Variables
  for (int i = 0; i < 8; i++) rc_raw_[i] = 0;
  chan_ = 0;
  current_capture_ = 0;
  last_capture_ = 0;
  last_pulse_ms_ = 0;

  TIM_ = conf->TIM;
  TIM_IT_ = conf->TIM_IT_CC;
  TIM_Channel_ = conf->TIM_Channel;

  // Connect the global pointer
  RC_PPM_Ptr = this;

  // Set up the Pin
  pin_.init(conf->GPIO, conf->GPIO_Pin, GPIO::PERIPH_IN);

  // Connect Pin to the timer peripherial
  GPIO_PinAFConfig(conf->GPIO, conf->GPIO_PinSource, conf->GIPO_AF_TIM);

  // Configure the timer
  TIM_TimeBaseInitTypeDef TIM_init_struct;
  TIM_init_struct.TIM_Period = 0xFFFF;                               // It'll get reset by the CC
  TIM_init_struct.TIM_ClockDivision = TIM_CKD_DIV1;                  // No clock division
  TIM_init_struct.TIM_Prescaler = (SystemCoreClock / (2000000)) - 1; // prescaler (0-indexed), set to 1 MHz
  TIM_init_struct.TIM_CounterMode = TIM_CounterMode_Up;              // count up
  TIM_TimeBaseInit(TIM_, &TIM_init_struct);

  // Configure the Input Compare Peripheral
  TIM_ICInitTypeDef TIM_IC_init_struct;
  TIM_IC_init_struct.TIM_Channel = TIM_Channel_;
  TIM_IC_init_struct.TIM_ICFilter = 0x00;
  TIM_IC_init_struct.TIM_ICPolarity = TIM_ICPolarity_Rising;
  TIM_IC_init_struct.TIM_ICPrescaler = TIM_ICPSC_DIV1;
  TIM_IC_init_struct.TIM_ICSelection = TIM_ICSelection_DirectTI;
  TIM_ICInit(TIM_, &TIM_IC_init_struct);

  // Set up the interrupt for the Timer
  NVIC_InitTypeDef NVIC_InitStructure;
  NVIC_InitStructure.NVIC_IRQChannel = conf->TIM_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x02;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x01;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

  // Enable the CC interrupt
  TIM_ITConfig(TIM_, TIM_IT_, ENABLE);

  // Start Counting!
  TIM_ARRPreloadConfig(TIM_, ENABLE);
  TIM_Cmd(TIM_, ENABLE);
}

float RC_PPM::read(uint8_t channel)
{
  return static_cast<float>(rc_raw_[channel] - 1000) / 1000.0;
}

bool RC_PPM::lost()
{
  return millis() > last_pulse_ms_ + 100;
}

void RC_PPM::pulse_callback()
{
  if (TIM_GetITStatus(TIM_, TIM_IT_))
  {
    TIM_ClearITPendingBit(TIM_, TIM_IT_);
    last_pulse_ms_ = millis();

    switch (TIM_Channel_)
    {
    case TIM_Channel_1:
    default:
      current_capture_ = TIM_GetCapture1(TIM_);
      break;
    case TIM_Channel_2:
      current_capture_ = TIM_GetCapture2(TIM_);
      break;
    case TIM_Channel_3:
      current_capture_ = TIM_GetCapture3(TIM_);
      break;
    case TIM_Channel_4:
      current_capture_ = TIM_GetCapture4(TIM_);
      break;
    }
    uint16_t diff = current_capture_ - last_capture_;
    last_capture_ = current_capture_;

    // We're on a new frame
    if (diff > 2500)
    {
      chan_ = 0;
    }
    else
    {
      // If it's a valid reading, then save it!
      if (diff > 750 && diff < 2250 && chan_ < 8)
      {
        rc_raw_[chan_] = diff;
      }
      chan_++;
    }
    if (chan_ > 8)
    {
      chan_ = 0;
      TIM_SetCounter(TIM_, 0);
    }
  }
}

extern "C"
{
  void PPM_RC_IQRHandler(void)
  {
    if (RC_PPM_Ptr != NULL)
    {
      RC_PPM_Ptr->pulse_callback();
    }
  }
}