arduino/arduino-LoRa
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Add getting the frequency error of a packet (#111)

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torntrousers 2018-03-19 00:02:47 +00:00 committed by Sandeep Mistry
parent f5cae9c25d
commit 27e2963c97
4 changed files with 51 additions and 0 deletions
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8
API.md
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@ -166,6 +166,14 @@ float snr = LoRa.packetSnr();
Returns the estimated SNR of the received packet in dB.
### Packet Frequency Error
```arduino
long freqErr = LoRa.packetFrequencyError();
```
Returns the frequency error of the received packet in Hz. The frequency error is the frequency offset between the receiver centre frequency and that of an incoming LoRa signal.
### Available
```arduino

1
keywords.txt
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@ -21,6 +21,7 @@ endPacket KEYWORD2
parsePacket KEYWORD2
packetRssi KEYWORD2
packetSnr KEYWORD2
packetFrequencyError KEYWORD2
write KEYWORD2

39
src/LoRa.cpp
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@ -25,6 +25,9 @@
#define REG_PREAMBLE_LSB 0x21
#define REG_PAYLOAD_LENGTH 0x22
#define REG_MODEM_CONFIG_3 0x26
#define REG_FREQ_ERROR_MSB 0x28
#define REG_FREQ_ERROR_MID 0x29
#define REG_FREQ_ERROR_LSB 0x2a
#define REG_RSSI_WIDEBAND 0x2c
#define REG_DETECTION_OPTIMIZE 0x31
#define REG_DETECTION_THRESHOLD 0x37
@ -211,6 +214,25 @@ float LoRaClass::packetSnr()
return ((int8_t)readRegister(REG_PKT_SNR_VALUE)) * 0.25;
}
long LoRaClass::packetFrequencyError()
{
int32_t freqError = 0;
freqError = static_cast<int32_t>(readRegister(REG_FREQ_ERROR_MSB) & B111);
freqError <<= 8L;
freqError += static_cast<int32_t>(readRegister(REG_FREQ_ERROR_MID));
freqError <<= 8L;
freqError += static_cast<int32_t>(readRegister(REG_FREQ_ERROR_LSB));
if (readRegister(REG_FREQ_ERROR_MSB) & B1000) { // Sign bit is on
freqError -= 524288; // B1000'0000'0000'0000'0000
}
const float fXtal = 32E6; // FXOSC: crystal oscillator (XTAL) frequency (2.5. Chip Specification, p. 14)
const float fError = ((static_cast<float>(freqError) * (1L << 24)) / fXtal) * (getSignalBandwidth() / 500000.0f); // p. 37
return static_cast<long>(fError);
}
size_t LoRaClass::write(uint8_t byte)
{
return write(&byte, sizeof(byte));
@ -370,6 +392,23 @@ void LoRaClass::setSpreadingFactor(int sf)
writeRegister(REG_MODEM_CONFIG_2, (readRegister(REG_MODEM_CONFIG_2) & 0x0f) | ((sf << 4) & 0xf0));
}
long LoRaClass::getSignalBandwidth()
{
byte bw = (readRegister(REG_MODEM_CONFIG_1) >> 4);
switch (bw) {
case 0: return 7.8E3;
case 1: return 10.4E3;
case 2: return 15.6E3;
case 3: return 20.8E3;
case 4: return 31.25E3;
case 5: return 41.7E3;
case 6: return 62.5E3;
case 7: return 125E3;
case 8: return 250E3;
case 9: return 500E3;
}
}
void LoRaClass::setSignalBandwidth(long sbw)
{
int bw;

3
src/LoRa.h
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@ -27,6 +27,7 @@ public:
int parsePacket(int size = 0);
int packetRssi();
float packetSnr();
long packetFrequencyError();
// from Print
virtual size_t write(uint8_t byte);
@ -71,6 +72,8 @@ private:
void handleDio0Rise();
long getSignalBandwidth();
uint8_t readRegister(uint8_t address);
void writeRegister(uint8_t address, uint8_t value);
uint8_t singleTransfer(uint8_t address, uint8_t value);