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Merge pull request #83 from BarryPSmith/sx126x_integer_lite

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Removed some sx126x floating point logic to save code space
This commit is contained in:
Jan Gromeš 2019-12-04 18:10:39 +01:00 • committed by GitHub
commit 4d5e0c6557
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 65 additions and 34 deletions
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99
src/modules/SX126x/SX126x.cpp
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@ -176,11 +176,11 @@ int16_t SX126x::transmit(uint8_t* data, size_t len, uint8_t addr) {
uint8_t modem = getPacketType();
if(modem == SX126X_PACKET_TYPE_LORA) {
// calculate timeout (150% of expected time-on-air)
timeout = (float)getTimeOnAir(len) * 1.5;
timeout = (getTimeOnAir(len) * 3) / 2;
} else if(modem == SX126X_PACKET_TYPE_GFSK) {
// calculate timeout (500% of expected time-on-air)
timeout = (float)getTimeOnAir(len) * 5.0;
timeout = getTimeOnAir(len) * 5;
} else {
return(ERR_UNKNOWN);
@ -505,31 +505,48 @@ int16_t SX126x::setBandwidth(float bw) {
return(ERR_WRONG_MODEM);
}
// check alowed bandwidth values
if(abs(bw - 7.8) <= 0.001) {
_bw = SX126X_LORA_BW_7_8;
} else if(abs(bw - 10.4) <= 0.001) {
_bw = SX126X_LORA_BW_10_4;
} else if(abs(bw - 15.6) <= 0.001) {
_bw = SX126X_LORA_BW_15_6;
} else if(abs(bw - 20.8) <= 0.001) {
_bw = SX126X_LORA_BW_20_8;
} else if(abs(bw - 31.25) <= 0.001) {
_bw = SX126X_LORA_BW_31_25;
} else if(abs(bw - 41.7) <= 0.001) {
_bw = SX126X_LORA_BW_41_7;
} else if(abs(bw - 62.5) <= 0.001) {
_bw = SX126X_LORA_BW_62_5;
} else if(abs(bw - 125.0) <= 0.001) {
_bw = SX126X_LORA_BW_125_0;
} else if(abs(bw - 250.0) <= 0.001) {
_bw = SX126X_LORA_BW_250_0;
} else if(abs(bw - 500.0) <= 0.001) {
_bw = SX126X_LORA_BW_500_0;
} else {
// ensure byte conversion doesn't overflow:
if(!((bw > 0) && (bw < 510))) {
return(ERR_INVALID_BANDWIDTH);
}
// check alowed bandwidth values
uint8_t bw_div2 = bw / 2 + 0.01;
switch (bw_div2) {
case 3: // 7.8:
_bw = SX126X_LORA_BW_7_8;
break;
case 5: // 10.4:
_bw = SX126X_LORA_BW_10_4;
break;
case 7: // 15.6:
_bw = SX126X_LORA_BW_15_6;
break;
case 10: // 20.8:
_bw = SX126X_LORA_BW_20_8;
break;
case 15: // 31.25:
_bw = SX126X_LORA_BW_31_25;
break;
case 20: // 41.7:
_bw = SX126X_LORA_BW_41_7;
break;
case 31: // 62.5:
_bw = SX126X_LORA_BW_62_5;
break;
case 62: // 125.0:
_bw = SX126X_LORA_BW_125_0;
break;
case 125: // 250.0
_bw = SX126X_LORA_BW_250_0;
break;
case 250: // 500.0
_bw = SX126X_LORA_BW_500_0;
break;
default:
return(ERR_INVALID_BANDWIDTH);
}
// update modulation parameters
_bwKhz = bw;
return(setModulationParams(_sf, _bw, _cr));
@ -984,23 +1001,37 @@ int16_t SX126x::variablePacketLengthMode(uint8_t maxLen) {
}
uint32_t SX126x::getTimeOnAir(size_t len) {
// everything is in microseconds to allow integer arithmetic
// some constants have .25, these are multiplied by 4, and have _x4 postfix to indicate that fact
if(getPacketType() == SX126X_PACKET_TYPE_LORA) {
float symbolLength = (float)((uint32_t)(1) << _sf) / (float)_bwKhz;
float sfCoeff1 = 4.25;
float sfCoeff2 = 8.0;
uint32_t symbolLength_us = ((uint32_t)(1000 * 10) << _sf) / (_bwKhz * 10) ;
uint8_t sfCoeff1_x4 = 17; // (4.25 * 4)
uint8_t sfCoeff2 = 8;
if(_sf == 5 || _sf == 6) {
sfCoeff1 = 6.25;
sfCoeff2 = 0.0;
sfCoeff1_x4 = 25; // 6.25 * 4
sfCoeff2 = 0;
}
uint8_t sfDivisor = 4*_sf;
if(symbolLength >= 16.0) {
if(symbolLength_us >= 16000) {
sfDivisor = 4*(_sf - 2);
}
float nSymbol = _preambleLength + sfCoeff1 + 8 + ceil(max(8.0 * len + (_crcType * 16.0) - 4.0 * _sf + sfCoeff2 + 20.0, 0.0) / sfDivisor) * (_cr + 4);
return((uint32_t)(symbolLength * nSymbol * 1000.0));
const int8_t bitsPerCrc = 16;
const int8_t N_symbol_header = 20;
// numerator of equation in section 6.1.4 of SX1268 datasheet v1.1 (might not actually be bitcount, but it has len * 8)
int16_t bitCount = (int16_t) 8 * len + _crcType * bitsPerCrc - 4 * _sf + sfCoeff2 + N_symbol_header;
if(bitCount < 0) {
bitCount = 0;
}
// add (sfDivisor) - 1 to the numerator to give integer CEIL(...)
uint16_t nPreCodedSymbols = (bitCount + (sfDivisor - 1)) / (sfDivisor);
// preamble can be 65k, therefore nSymbol_x4 needs to be 32 bit
uint32_t nSymbol_x4 = (_preambleLength + 8) * 4 + sfCoeff1_x4 + nPreCodedSymbols * (_cr + 4) * 4;
return((symbolLength_us * nSymbol_x4) / 4);
} else {
float brBps = ((float)(SX126X_CRYSTAL_FREQ) * 1000000.0 * 32.0) / (float)_br;
return((uint32_t)(((len * 8.0) / brBps) * 1000000.0));
return((len * 8 * _br) / (SX126X_CRYSTAL_FREQ * 32));
}
}