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Roughing out concept of patent based temp curve
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Ben V. Brown
@@ -16,6 +16,7 @@
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#include "stdlib.h"
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#include "stm32f1xx_hal.h"
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#include "string.h"
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#include "TipThermoModel.h"
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extern uint8_t PCBVersion;
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// File local variables
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extern uint32_t currentlyActiveTemperatureTarget;
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@@ -647,7 +648,7 @@ void showDebugMenu(void) {
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break;
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case 6:
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//Raw Tip
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OLED::printNumber(getTipRawTemp(0), 6);
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OLED::printNumber(TipThermoModel::convertTipRawADCToDegC(getTipRawTemp(0)), 6);
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break;
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case 7:
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//Temp in C
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205
workspace/TS100/Core/Src/TipThermoModel.cpp
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205
workspace/TS100/Core/Src/TipThermoModel.cpp
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@@ -0,0 +1,205 @@
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/*
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* TipThermoModel.cpp
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*
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* Created on: 7 Oct 2019
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* Author: ralim
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*/
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#include "TipThermoModel.h"
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/*
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* The hardware is laid out as a non-inverting op-amp
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* There is a pullup of 39k(TS100) from the +ve input to 3.9V (1M pulup on TS100)
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*
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* The simplest case to model this, is to ignore the pullup resistors influence, and assume that its influence is mostly constant
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* -> Tip resistance *does* change with temp, but this should be much less than the rest of the system.
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*
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* When a thermocouple is equal temperature at both sides (hot and cold junction), then the output should be 0uV
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* Therefore, by measuring the uV when both are equal, the measured reading is the offset value.
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* This is a mix of the pull-up resistor, combined with tip manufacturing differences.
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*
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* All of the thermocouple readings are based on this expired patent
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* - > https://patents.google.com/patent/US6087631A/en
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*
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* This was bought to my attention by <Kuba Sztandera>
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*/
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#ifdef MODEL_TS100
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#define OP_AMP_Rf 750*1000 /*750 Kilo-ohms -> From schematic, R1*/
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#define OP_AMP_Rin 2370 /*2.37 Kilo-ohms -> From schematic, R2*/
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#else
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#define OP_AMP_Rf 180*1000 /*180 Kilo-ohms -> From schematic, R6*/
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#define OP_AMP_Rin 2000 /*2.0 Kilo-ohms -> From schematic, R3*/
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#endif
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#define op_amp_gain_stage (1+(OP_AMP_Rf/OP_AMP_Rin))
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uint32_t TipThermoModel::convertTipRawADCTouV(uint16_t rawADC) {
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// This takes the raw ADC samples, converts these to uV
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// Then divides this down by the gain to convert to the uV on the input to the op-amp (A+B terminals)
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// Then remove the calibration value that is stored as a tip offset
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uint32_t vddRailmVX10 = 33000; //TODO use ADC Vref to calculate this
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// 4096 * 8 readings for full scale
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// Convert the input ADC reading back into mV times 10 format.
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uint32_t rawInputmVX10 = (rawADC * vddRailmVX10) / (4096 * 8);
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uint32_t valueuV = rawInputmVX10 * 100; // shift into uV
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//Now to divide this down by the gain
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valueuV = (valueuV) / op_amp_gain_stage;
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//Remove uV tipOffset
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//TODO
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return valueuV;
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}
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uint32_t TipThermoModel::convertTipRawADCToDegC(uint16_t rawADC) {
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return convertuVToDegC(convertTipRawADCTouV(rawADC));
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}
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//Table that is designed to be walked to find the best sample for the lookup
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struct HakkoThermocoupleLookup {
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// 0 is the uV reading
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// 1 is the deg C X10
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// This was created from numbers transcribed from the patent by <Kuba Sztandera>
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constexpr HakkoThermocoupleLookup() :
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values() {
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values[0][0] = 0;
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values[0][1] = 0;
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values[1][0] = 175;
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values[1][1] = 100;
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values[2][0] = 381;
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values[2][1] = 200;
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values[3][0] = 587;
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values[3][1] = 300;
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values[4][0] = 804;
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values[4][1] = 400;
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values[5][0] = 1005;
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values[5][1] = 500;
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values[6][0] = 1007;
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values[6][1] = 600;
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values[7][0] = 1107;
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values[7][1] = 700;
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values[8][0] = 1310;
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values[8][1] = 800;
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values[9][0] = 1522;
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values[9][1] = 900;
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values[10][0] = 1731;
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values[10][1] = 1000;
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values[11][0] = 1939;
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values[11][1] = 1100;
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values[12][0] = 2079;
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values[12][1] = 1200;
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values[13][0] = 2265;
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values[13][1] = 1300;
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values[14][0] = 2470;
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values[14][1] = 1400;
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values[15][0] = 2676;
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values[15][1] = 1500;
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values[16][0] = 2899;
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values[16][1] = 1600;
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values[17][0] = 3081;
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values[17][1] = 1700;
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values[18][0] = 3186;
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values[18][1] = 1800;
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values[19][0] = 3422;
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values[19][1] = 1900;
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values[20][0] = 3622;
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values[20][1] = 2000;
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values[21][0] = 3830;
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values[21][1] = 2100;
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values[22][0] = 4044;
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values[22][1] = 2200;
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values[23][0] = 4400;
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values[23][1] = 2300;
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values[24][0] = 4691;
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values[24][1] = 2400;
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values[25][0] = 4989;
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values[25][1] = 2500;
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values[26][0] = 5289;
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values[26][1] = 2600;
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values[27][0] = 5583;
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values[27][1] = 2700;
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values[28][0] = 5879;
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values[28][1] = 2800;
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values[29][0] = 6075;
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values[29][1] = 2900;
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values[30][0] = 6332;
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values[30][1] = 3000;
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values[31][0] = 6521;
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values[31][1] = 3100;
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values[32][0] = 6724;
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values[32][1] = 3200;
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values[33][0] = 6929;
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values[33][1] = 3300;
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values[34][0] = 7132;
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values[34][1] = 3400;
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values[35][0] = 7356;
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values[35][1] = 3500;
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values[36][0] = 7561;
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values[36][1] = 3600;
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values[37][0] = 7774;
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values[37][1] = 3700;
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values[38][0] = 7992;
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values[38][1] = 3800;
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values[39][0] = 8200;
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values[39][1] = 3900;
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values[40][0] = 8410;
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values[40][1] = 4000;
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values[41][0] = 8626;
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values[41][1] = 4100;
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values[42][0] = 8849;
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values[42][1] = 4200;
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values[43][0] = 9060;
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values[43][1] = 4300;
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values[44][0] = 9271;
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values[44][1] = 4400;
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values[45][0] = 9531;
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values[45][1] = 4500;
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values[46][0] = 9748;
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values[46][1] = 4600;
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values[47][0] = 10210;
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values[47][1] = 4700;
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values[48][0] = 10219;
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values[48][1] = 4800;
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values[49][0] = 10429;
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values[49][1] = 4900;
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values[50][0] = 10649;
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values[50][1] = 5000;
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}
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uint32_t count = 51;
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uint32_t values[51][2];
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};
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constexpr auto ThermalTable = HakkoThermocoupleLookup();
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//Extrapolate between two points
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// [x1, y1] = point 1
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// [x2, y2] = point 2
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// x = input value
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// output is x's extrapolated y value
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int32_t LinearInterpolate(int32_t x1, int32_t y1, int32_t x2, int32_t y2,
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int32_t x) {
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return y1 + (((((x - x1) * 1000) / (x2 - x1)) * (y2 - y1))) / 1000;
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}
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uint32_t TipThermoModel::convertuVToDegC(uint32_t tipuVDelta) {
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//Perform lookup on table of values to find the closest two measurement points, and then linearly interpolate these
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//This assumes results in the table are increasing order
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// TODO -> Should this be made into a binary search? Is it much faster??
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for (uint32_t i = 1; i < ThermalTable.count; i++) {
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if (((uint32_t) ThermalTable.values[i][0]) < tipuVDelta) {
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//Then extrapolate
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//Where i= the lower raw sample, i-1 is the higher raw sample
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return LinearInterpolate( //
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ThermalTable.values[i][0], // x1
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ThermalTable.values[i][1], // y1
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ThermalTable.values[i - 1][0], // x2
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ThermalTable.values[i - 1][1], // y2
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tipuVDelta); // raw sample to be interpolated
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}
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}
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return 5000;
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}
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20
workspace/TS100/Core/Src/TipThermoModel.h
Normal file
20
workspace/TS100/Core/Src/TipThermoModel.h
Normal file
@@ -0,0 +1,20 @@
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/*
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* TipThermoModel.h
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*
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* Created on: 7 Oct 2019
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* Author: ralim
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*/
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#ifndef SRC_TIPTHERMOMODEL_H_
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#define SRC_TIPTHERMOMODEL_H_
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#include "stdint.h"
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#include "hardware.h"
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class TipThermoModel {
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public:
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//Returns the uV of the tip reading before the op-amp compensating for pullups
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static uint32_t convertTipRawADCTouV(uint16_t rawADC);
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static uint32_t convertTipRawADCToDegC(uint16_t rawADC);
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static uint32_t convertuVToDegC(uint32_t tipuVDelta);
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};
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#endif /* SRC_TIPTHERMOMODEL_H_ */
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