Far better tip resistance measurement

This commit is contained in:
Ben V. Brown
2022-07-10 14:49:17 +10:00
parent a93a477bd9
commit 9b22c27e03

View File

@@ -226,11 +226,12 @@ void setStatusLED(const enum StatusLED state) {
// Dont have one
}
uint8_t lastTipResistance = 0; // default to unknown
uint32_t tipResistanceReadings[4] = {0, 0, 0, 0};
uint8_t tipResistanceReadingSlot = 0;
uint8_t getTipResitanceX10() {
// Return tip resistance in x10 ohms
uint8_t lastTipResistance = 0; // default to unknown
const uint8_t numTipResistanceReadings = 3;
uint32_t tipResistanceReadings[3] = {0, 0, 0};
uint8_t tipResistanceReadingSlot = 0;
uint8_t getTipResitanceX10() {
// Return tip resistance in x10 ohms
// We can measure this using the op-amp
return lastTipResistance;
}
@@ -255,30 +256,25 @@ uint8_t getTipThermalMass() {
void performTipResistanceSampleReading() {
// 0 = read then turn on pullup, 1 = read then turn off pullup, 2 = read then turn on pullup, 3 = final read + turn off pullup
tipResistanceReadings[tipResistanceReadingSlot] = TipThermoModel::convertTipRawADCTouV(getTipRawTemp(0));
gpio_write(TIP_RESISTANCE_SENSE, (tipResistanceReadingSlot % 2) ? 0 : 1);
gpio_write(TIP_RESISTANCE_SENSE, tipResistanceReadingSlot == 0);
tipResistanceReadingSlot++;
}
void FinishMeasureTipResistance() {
// Otherwise we now have the 4 samples;
// _^_^ order, 3 delta's, combine these
// _^_ order, 2 delta's, combine these
int32_t steps[4] = {
// Close samples
tipResistanceReadings[1] - tipResistanceReadings[0],
tipResistanceReadings[3] - tipResistanceReadings[2],
tipResistanceReadings[1] - tipResistanceReadings[2],
// Longer time span samples
tipResistanceReadings[3] - tipResistanceReadings[0],
int32_t calculatedSkew = tipResistanceReadings[0] - tipResistanceReadings[2]; // If positive tip is cooling
calculatedSkew /= 2; // divide by two to get offset per time constant
};
// The steps array now contains all 4 changes, these _should_ all be basically the same, but they may not be
// For example, a hot tip cooling down. In this case there will a difference in them proportional to the temp drop during that time
auto reading = (steps[0] + steps[1] + steps[2] + steps[3]) / 4;
// MSG("Tip reading %lu \r\n");
// As we are only detecting two resistances; we can split the difference for now
int32_t reading = (((tipResistanceReadings[1] - tipResistanceReadings[0]) + calculatedSkew) // jump 1 - skew
+ // +
((tipResistanceReadings[1] - tipResistanceReadings[2]) + calculatedSkew) // jump 2 - skew
) //
/ 2; // Take average
// lastTipResistance = reading / 100;
// // As we are only detecting two resistances; we can split the difference for now
uint8_t newRes = 0;
if (reading > 8000) {
// return; // Change nothing as probably disconnected tip
@@ -299,7 +295,7 @@ void performTipMeasurementStep() {
return;
}
nextTipMeasurement = xTaskGetTickCount() + TICKS_100MS;
if (tipResistanceReadingSlot < 4) {
if (tipResistanceReadingSlot < numTipResistanceReadings) {
performTipResistanceSampleReading();
return;
}
@@ -314,7 +310,7 @@ uint8_t preStartChecks() {
performTipMeasurementStep();
return preStartChecksDone();
}
uint8_t preStartChecksDone() { return (lastTipResistance == 0 || tipResistanceReadingSlot < 4 || tipMeasurementOccuring) ? 0 : 1; }
uint8_t preStartChecksDone() { return (lastTipResistance == 0 || tipResistanceReadingSlot < numTipResistanceReadings || tipMeasurementOccuring) ? 0 : 1; }
// Return hardware unique ID if possible
uint64_t getDeviceID() {