Grove-Lora Radio：修改库函数使能修改扩频因子、带宽参数、码率

Grove-Lora Radio的使用详见：http://wiki.seeedstudio.com/cn/Grove_LoRa_Radio/

但是网站中提供的Grove_LoRa_433MHz_and_915MHz_RF-master中的示例代码只能修改RF的频率，不能修改LoRa扩频因子、带宽等参数。研究了一下午，终于搞明白怎么修改库函数，特在此记录。

注意！必须找到与Grove_LoRa_433MHz_and_915MHz_RF-master库对应的 RH_RF95.h和 RH_RF95.cpp文件！

1. 修改扩频因子，添加如下代码段

① RH_RF95.cpp，添加

template 
void RH_RF95::setSpreadingFactor(int8_t sf)
{
  if (sf < 6) {
    sf = 6;
  } else if (sf > 12) {
    sf = 12;
  }

  if (sf == 6) {
    this->write(RH_RF95_REG_31_DETECTION_OPTIMIZE, 0xc5);
    this->write(RH_RF95_REG_37_DETECTION_THRESHOLD, 0x0c);
  } else {
    this->write(RH_RF95_REG_31_DETECTION_OPTIMIZE, 0xc3);
    this->write(RH_RF95_REG_37_DETECTION_THRESHOLD, 0x0a);
  }

  this->write(RH_RF95_REG_1E_MODEM_CONFIG2, (this->read(RH_RF95_REG_1E_MODEM_CONFIG2) & 0x0f) | ((sf << 4) & 0xf0));
}

② RH_RF95.h，添加

#define RH_RF95_REG_31_DETECTION_OPTIMIZE   0x31
#define RH_RF95_REG_37_DETECTION_THRESHOLD  0x37

void setSpreadingFactor(int8_t sf);

2. 修改带宽

① RH_RF95.cpp，添加

template 
void RH_RF95::setSignalBandwidth(long sbw)
{
  int bw;

  if (sbw <= 7.8E3) {
    bw = 0;
  } else if (sbw <= 10.4E3) {
    bw = 1;
  } else if (sbw <= 15.6E3) {
    bw = 2;
  } else if (sbw <= 20.8E3) {
    bw = 3;
  } else if (sbw <= 31.25E3) {
    bw = 4;
  } else if (sbw <= 41.7E3) {
    bw = 5;
  } else if (sbw <= 62.5E3) {
    bw = 6;
  } else if (sbw <= 125E3) {
    bw = 7;
  } else if (sbw <= 250E3) {
    bw = 8;
  } else /*if (sbw <= 250E3)*/ {
    bw = 9;
  }

  this->write(RH_RF95_REG_1D_MODEM_CONFIG1, (this->read(RH_RF95_REG_1D_MODEM_CONFIG1) & 0x0f) | (bw << 4));
}

② RH_RF95.h，添加

void setSignalBandwidth(long sbw);

3. 修改码率

① RH_RF95.cpp，添加

template 
void RH_RF95::setCodingRate4(int8_t denominator)
{
  if (denominator < 5) {
    denominator = 5;
  } else if (denominator > 8) {
    denominator = 8;
  }
  int cr = denominator - 4;
  this->write(RH_RF95_REG_1D_MODEM_CONFIG1, (this->read(RH_RF95_REG_1D_MODEM_CONFIG1) & 0xf1) | (cr << 1));
}

② RH_RF95.h，添加

void setCodingRate4(int8_t denominator);