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/*
* Thermistor.cpp
* Reads temperature from a thermistor or a PT1000 sensor connected to a thermistor port
*
* Created on: 10 Nov 2016
* Author: David
*/
#include "Thermistor.h"
#include "Platform.h"
#include "RepRap.h"
#include "GCodes/GCodeBuffer/GCodeBuffer.h"
// The Steinhart-Hart equation for thermistor resistance is:
// 1/T = A + B ln(R) + C [ln(R)]^3
//
// The simplified (beta) equation assumes C=0 and is:
// 1/T = A + (1/Beta) ln(R)
//
// The parameters that can be configured in RRF are R25 (the resistance at 25C), Beta, and optionally C.
// Create an instance with default values
Thermistor::Thermistor(unsigned int sensorNum, bool p_isPT1000) noexcept
: SensorWithPort(sensorNum, (p_isPT1000) ? "PT1000" : "Thermistor"),
r25(DefaultR25), beta(DefaultBeta), shC(DefaultShc), seriesR(DefaultThermistorSeriesR), adcFilterChannel(-1), isPT1000(p_isPT1000)
#if !HAS_VREF_MONITOR || defined(DUET3)
, adcLowOffset(0), adcHighOffset(0)
#endif
{
CalcDerivedParameters();
}
// Configure the temperature sensor
GCodeResult Thermistor::Configure(GCodeBuffer& gb, const StringRef& reply)
{
bool seen = false;
if (!ConfigurePort(gb, reply, PinAccess::readAnalog, seen))
{
return GCodeResult::error;
}
gb.TryGetFValue('R', seriesR, seen);
if (!isPT1000)
{
bool seenB = false;
gb.TryGetFValue('B', beta, seenB);
if (seenB)
{
shC = 0.0; // if user changes B and doesn't define C, assume C=0
seen = true;
}
gb.TryGetFValue('C', shC, seen);
gb.TryGetFValue('T', r25, seen);
if (seen)
{
CalcDerivedParameters();
}
}
#if !HAS_VREF_MONITOR || defined(DUET3)
constexpr int maxOffset = (int)(30u << (AdcBits + AdcOversampleBits - 12));
if (gb.Seen('L'))
{
adcLowOffset = (int16_t)constrain<int>(gb.GetIValue(), -maxOffset, maxOffset);
seen = true;
}
if (gb.Seen('H'))
{
adcHighOffset = (int16_t)constrain<int>(gb.GetIValue(), -maxOffset, maxOffset);
seen = true;
}
#endif
TryConfigureSensorName(gb, seen);
if (seen)
{
adcFilterChannel = reprap.GetPlatform().GetAveragingFilterIndex(port);
if (adcFilterChannel >= 0)
{
reprap.GetPlatform().GetAdcFilter(adcFilterChannel).Init((1u << AdcBits) - 1);
}
}
else
{
CopyBasicDetails(reply);
if (isPT1000)
{
// For a PT1000 sensor, only the series resistor is configurable
reply.catf(", R:%.1f", (double)seriesR);
}
else
{
reply.catf(", T:%.1f B:%.1f C:%.2e R:%.1f", (double)r25, (double)beta, (double)shC, (double)seriesR);
}
#if !HAS_VREF_MONITOR || defined(DUET3)
reply.catf(" L:%d H:%d", adcLowOffset, adcHighOffset);
#endif
}
return GCodeResult::ok;
}
// Get the temperature
void Thermistor::Poll() noexcept
{
int32_t averagedTempReading;
bool tempFilterValid;
if (adcFilterChannel >= 0)
{
const volatile ThermistorAveragingFilter& tempFilter = reprap.GetPlatform().GetAdcFilter(adcFilterChannel);
averagedTempReading = tempFilter.GetSum()/(tempFilter.NumAveraged() >> Thermistor::AdcOversampleBits);
tempFilterValid = tempFilter.IsValid();
}
else
{
averagedTempReading = (uint32_t)port.ReadAnalog() << Thermistor::AdcOversampleBits;
tempFilterValid = true;
}
#if HAS_VREF_MONITOR
// Use the actual VSSA and VREF values read by the ADC
const volatile ThermistorAveragingFilter& vrefFilter = reprap.GetPlatform().GetAdcFilter(VrefFilterIndex);
const volatile ThermistorAveragingFilter& vssaFilter = reprap.GetPlatform().GetAdcFilter(VssaFilterIndex);
if (tempFilterValid && vrefFilter.IsValid() && vssaFilter.IsValid())
{
# ifdef DUET3
// Duet 3 MB6HC board revisions 0.5, 0.6 and 1.0 have the series resistor connected to VrefP, not VrefMon.
// So Extrapolate the reading for VrefP. We also allow offsets to be added.
const int32_t rawAveragedVssaReading = vssaFilter.GetSum()/(vssaFilter.NumAveraged() >> Thermistor::AdcOversampleBits);
const int32_t rawAveragedVrefReading = vrefFilter.GetSum()/(vrefFilter.NumAveraged() >> Thermistor::AdcOversampleBits);
const int32_t averagedVssaReading = rawAveragedVssaReading + (2 * adcLowOffset);
const int32_t averagedVrefReading = ((rawAveragedVrefReading - rawAveragedVssaReading) * 4715)/4700 + rawAveragedVssaReading + (2 * adcHighOffset);
# else
const int32_t averagedVssaReading = vssaFilter.GetSum()/(vssaFilter.NumAveraged() >> Thermistor::AdcOversampleBits);
const int32_t averagedVrefReading = vrefFilter.GetSum()/(vrefFilter.NumAveraged() >> Thermistor::AdcOversampleBits);
# endif
// VREF is the measured voltage at VREF less the drop of a 15 ohm resistor.
// VSSA is the voltage measured across the VSSA fuse. We assume the same 15 ohms maximum resistance for the fuse.
// Assume a maximum ADC reading offset of 100.
constexpr int32_t maxDrop = ((OversampledAdcRange * 15)/(int32_t)MinVrefLoadR) + (100 << Thermistor::AdcOversampleBits);
if (averagedVrefReading < OversampledAdcRange - maxDrop)
{
SetResult(TemperatureError::badVref);
}
else if (averagedVssaReading > maxDrop)
{
SetResult(TemperatureError::badVssa);
}
else
{
#else
if (tempFilterValid)
{
{
#endif
// Calculate the resistance
#if HAS_VREF_MONITOR
if (averagedVrefReading <= averagedTempReading)
{
SetResult((isPT1000) ? BadErrorTemperature : ABS_ZERO, TemperatureError::openCircuit);
}
else if (averagedTempReading <= averagedVssaReading)
{
SetResult(BadErrorTemperature, TemperatureError::shortCircuit);
}
else
{
const float resistance = seriesR * (float)(averagedTempReading - averagedVssaReading)/(float)(averagedVrefReading - averagedTempReading);
#else
const int32_t averagedVrefReading = OversampledAdcRange + 2 * adcHighOffset; // double the offset because we increased AdcOversampleBits from 1 to 2
if (averagedVrefReading <= averagedTempReading)
{
SetResult((isPT1000) ? BadErrorTemperature : ABS_ZERO, TemperatureError::openCircuit);
}
else
{
const float denom = (float)(averagedVrefReading - averagedTempReading) - 0.5;
const int32_t averagedVssaReading = 2 * adcLowOffset; // double the offset because we increased AdcOversampleBits from 1 to 2
float resistance = seriesR * ((float)(averagedTempReading - averagedVssaReading) + 0.5)/denom;
# ifdef DUET_NG
// The VSSA PTC fuse on the later Duets has a resistance of a few ohms. I measured 1.0 ohms on two revision 1.04 Duet WiFi boards.
resistance -= 1.0; // assume 1.0 ohms and only one PT1000 sensor
# endif
#endif
if (isPT1000)
{
// We want 100 * the equivalent PT100 resistance, which is 10 * the actual PT1000 resistance
const uint16_t ohmsx100 = (uint16_t)lrintf(constrain<float>(resistance * 10, 0.0, 65535.0));
float t;
const TemperatureError sts = GetPT100Temperature(t, ohmsx100);
SetResult(t, sts);
}
else
{
// Else it's a thermistor
const float logResistance = log(resistance);
const float recipT = shA + shB * logResistance + shC * logResistance * logResistance * logResistance;
const float temp = (recipT > 0.0) ? (1.0/recipT) + ABS_ZERO : BadErrorTemperature;
if (temp < MinimumConnectedTemperature)
{
// Assume thermistor is disconnected
SetResult(ABS_ZERO, TemperatureError::openCircuit);
}
else
{
SetResult(temp, TemperatureError::success);
}
}
}
}
}
else
{
// Filter is not ready yet
SetResult(TemperatureError::notReady);
}
}
// Calculate shA and shB from the other parameters
void Thermistor::CalcDerivedParameters() noexcept
{
shB = 1.0/beta;
const float lnR25 = logf(r25);
shA = 1.0/(25.0 - ABS_ZERO) - shB * lnR25 - shC * lnR25 * lnR25 * lnR25;
}
// End
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