/*
 * Copyright (C) OpenTX
 *
 * Based on code named
 *   th9x - http://code.google.com/p/th9x
 *   er9x - http://code.google.com/p/er9x
 *   gruvin9x - http://code.google.com/p/gruvin9x
 *
 * License GPLv2: http://www.gnu.org/licenses/gpl-2.0.html
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include "opentx.h"

#define CROSSFIRE_CH_BITS           11
#define CROSSFIRE_CENTER            0x3E0
#if defined(PPM_CENTER_ADJUSTABLE)
  #define CROSSFIRE_CENTER_CH_OFFSET(ch)            ((2 * limitAddress(ch)->ppmCenter) + 1)  // + 1 is for rouding
#else
  #define CROSSFIRE_CENTER_CH_OFFSET(ch)            (0)
#endif


uint8_t createCrossfireModelIDFrame(uint8_t * frame)
{
  uint8_t * buf = frame;
  *buf++ = UART_SYNC;                                 /* device address */
  *buf++ = 8;                                         /* frame length */
  *buf++ = COMMAND_ID;                                /* cmd type */
  *buf++ = MODULE_ADDRESS;                            /* Destination Address */
  *buf++ = RADIO_ADDRESS;                             /* Origin Address */
  *buf++ = SUBCOMMAND_CRSF;                           /* sub command */
  *buf++ = COMMAND_MODEL_SELECT_ID;                   /* command of set model/receiver id */
  *buf++ = g_model.header.modelId[EXTERNAL_MODULE];   /* model ID */
  *buf++ = crc8_BA(frame + 2, 6);
  *buf++ = crc8(frame + 2, 7);
  return buf - frame;
}

// Range for pulses (channels output) is [-1024:+1024]
uint8_t createCrossfireChannelsFrame(uint8_t * frame, int16_t * pulses)
{
  uint8_t * buf = frame;
  *buf++ = MODULE_ADDRESS;
  *buf++ = 24; // 1(ID) + 22 + 1(CRC)
  uint8_t * crc_start = buf;
  *buf++ = CHANNELS_ID;
  uint32_t bits = 0;
  uint8_t bitsavailable = 0;
  for (int i=0; i<CROSSFIRE_CHANNELS_COUNT; i++) {
    uint32_t val = limit(0, CROSSFIRE_CENTER + (CROSSFIRE_CENTER_CH_OFFSET(i) * 4) / 5 + (pulses[i] * 4) / 5, 2 * CROSSFIRE_CENTER);
    bits |= val << bitsavailable;
    bitsavailable += CROSSFIRE_CH_BITS;
    while (bitsavailable >= 8) {
      *buf++ = bits;
      bits >>= 8;
      bitsavailable -= 8;
    }
  }
  *buf++ = crc8(crc_start, 23);
  return buf - frame;
}

void setupPulsesCrossfire()
{
  if (telemetryProtocol == PROTOCOL_TELEMETRY_CROSSFIRE) {
    uint8_t * pulses = extmodulePulsesData.crossfire.pulses;
#if defined(LUA)
    if (outputTelemetryBuffer.destination == TELEMETRY_ENDPOINT_SPORT) {
      memcpy(pulses, outputTelemetryBuffer.data, outputTelemetryBuffer.size);
      extmodulePulsesData.crossfire.length = outputTelemetryBuffer.size;
      outputTelemetryBuffer.reset();
    }
    else
#endif
    {
      if (moduleState[EXTERNAL_MODULE].counter == CRSF_FRAME_MODELID) {
        extmodulePulsesData.crossfire.length = createCrossfireModelIDFrame(pulses);
        moduleState[EXTERNAL_MODULE].counter = CRSF_FRAME_MODELID_SENT;
      }
      else {
        extmodulePulsesData.crossfire.length = createCrossfireChannelsFrame(pulses, &channelOutputs[g_model.moduleData[EXTERNAL_MODULE].channelsStart]);
      }
    }
  }
}