sfm_commands.hpp

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#pragma once
 
#include <cstddef>
#include <cstdint>
 
namespace sfm {
 
namespace addr {
constexpr uint8_t kSfm4300Default = 0x2A;  
constexpr uint8_t kSfm4300Alt1 = 0x2B;     
constexpr uint8_t kSfm4300Alt2 = 0x2C;     
constexpr uint8_t kSfm4300Alt3 = 0x2D;     
constexpr uint8_t kSfm3119 = 0x29;
constexpr uint8_t kSfm3003 = 0x28;        
constexpr uint8_t kSfm3003Ce = 0x2D;      
constexpr uint8_t kSfm3013 = 0x2F;
constexpr uint8_t kSfm3019 = 0x2E;
constexpr uint8_t kSfm6000Default = 0x24;  
constexpr uint8_t kSfm6000R560 = 0x23;     
constexpr uint8_t kSfm6000R1k2 = 0x22;     
constexpr uint8_t kSfm6000R2k7 = 0x21;     
constexpr uint8_t kSfm6000R5k6 = 0x20;     
constexpr uint8_t kSfm6000R12k = 0x42;     
constexpr uint8_t kSfm6000R27k = 0x41;     
constexpr uint8_t kGeneralCall = 0x00;  
}  // namespace addr
 
namespace cmd {
// SF06 (SFM4300) start codes — gas meaning is SF06's.
constexpr uint16_t kStartO2 = 0x3603;
constexpr uint16_t kStartAir = 0x3608;
constexpr uint16_t kStartN2O = 0x3615;
constexpr uint16_t kStartCO2 = 0x361E;
constexpr uint16_t kStartAirO2Mix = 0x3632;   
constexpr uint16_t kStartN2OO2Mix = 0x3639;   
constexpr uint16_t kStartCO2O2Mix = 0x3646;   
// SFx6000 start codes — calibrated gas index (interface reference §3.3.1, §3.5.1).
constexpr uint16_t kSfx6000StartGas0 = 0x3603;  
constexpr uint16_t kSfx6000StartGas1 = 0x3608;  
constexpr uint16_t kSfx6000StartGas2 = 0x3615;  
constexpr uint16_t kSfx6000StartGas3 = 0x361E;  
constexpr uint16_t kSfx6000StartGas4 = 0x3624;  
constexpr uint16_t kSfx6000StartMix0 = 0x3650;  
// SFx6000 output-buffer pointers (no measurement interruption).
constexpr uint16_t kSfx6000PointerGasInfo = 0xE151;    
constexpr uint16_t kSfx6000PointerTemperature = 0xE102; 
constexpr uint16_t kSfx6000PointerResult = 0xE000;      
constexpr uint16_t kUpdateConcentrationSet = 0xE17D;      
constexpr uint16_t kUpdateConcentrationActivate = 0xE000;
constexpr uint16_t kStopContinuous = 0x3FF9;
constexpr uint16_t kConfigureAveraging = 0x366A;          
constexpr uint16_t kReadScaleOffsetUnit = 0x3661;         
constexpr uint16_t kEnterSleep = 0x3677;
constexpr uint16_t kReadProductIdentifier = 0xE102;
constexpr uint8_t kGeneralCallReset = 0x06;               
}  // namespace cmd
 
namespace timing {
constexpr uint32_t kFirstResultAfterStartMs = 12;   
constexpr uint32_t kAccuracySettleAfterStartMs = 30; 
constexpr uint32_t kSoftResetMs = 20;               
constexpr uint32_t kWarmUpMs = 30;                  
constexpr uint32_t kMeasurementPeriodUs = 500;      
constexpr uint32_t kStopToIdleUs = 500;             
constexpr uint32_t kStopToIdleMs = 1;               
constexpr uint16_t kMaxAveragingWindow = 128;
constexpr uint32_t kSfx6000SoftResetMs = 30;          
constexpr uint32_t kSfx6000MeasurementPeriodUs = 1000; 
}  // namespace timing
 
constexpr uint16_t kFlowUnitSlm20C = 0x0148;
 
constexpr float kTemperatureScalePerC = 200.0f;
 
constexpr uint16_t kStatusPureGasFraction = 0x3FF;
 
constexpr uint8_t Crc8(const uint8_t* data, std::size_t len) noexcept {
    uint8_t crc = 0xFFU;
    for (std::size_t i = 0; i < len; ++i) {
        crc ^= data[i];
        for (int bit = 0; bit < 8; ++bit) {
            crc = static_cast<uint8_t>((crc & 0x80U) != 0U ? ((crc << 1) ^ 0x31U) : (crc << 1));
        }
    }
    return crc;
}
 
constexpr uint8_t Crc8Word(uint16_t word) noexcept {
    const uint8_t b[2] = {static_cast<uint8_t>(word >> 8), static_cast<uint8_t>(word & 0xFFU)};
    return Crc8(b, 2);
}
 
static_assert(Crc8Word(0xBEEF) == 0x92, "SF06 CRC-8 test vector (0xBEEF -> 0x92)");
 
}  // namespace sfm