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Ignore intermittent errors in the MAX31855K (and MAX6675) thermocouple sensor. #18039

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merged 2 commits into from
May 20, 2020
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Ignore intermittent errors in the MAX31855K (and MAX6675) thermocouple sensor. #18039

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f6418f5
Address #18025 -- ignore intermittent errors in MAX31855K. Require a…
mobilinkd May 19, 2020
6696fca
Update config macro name and fix undefined variable when only one the…
mobilinkd May 19, 2020
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13 changes: 13 additions & 0 deletions Marlin/Configuration_adv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,19 @@
//=============================Thermal Settings ============================
//===========================================================================

/**
* Thermocouple sensors are quite sensitive to noise. Any noise induced in
* the sensor wires, such as by stepper motor wires run in parallel to them,
* may result in the thermocouple sensor reporting spurious errors. This
* value is the number of errors which can occur in a row before the error
* is reported. This allows us to ignore intermittent error conditions while
* still detecting an actual failure, which should result in a continuous
* stream of errors from the sensor.
*
* Set this value to 0 to fail on the first error to occur.
*/
#define THERMOCOUPLE_MAX_ERRORS 15

//
// Custom Thermistor 1000 parameters
//
Expand Down
60 changes: 37 additions & 23 deletions Marlin/src/module/temperature.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2060,6 +2060,10 @@ void Temperature::disable_all_heaters() {

#if HAS_MAX6675

#ifndef THERMOCOUPLE_MAX_ERRORS
#define THERMOCOUPLE_MAX_ERRORS 15
#endif

int Temperature::read_max6675(
#if COUNT_6675 > 1
const uint8_t hindex
Expand All @@ -2071,6 +2075,8 @@ void Temperature::disable_all_heaters() {
// Needed to return the correct temp when this is called too soon
static uint16_t max6675_temp_previous[COUNT_6675] = { 0 };
#endif

static uint8_t max6675_errors[COUNT_6675] = { 0 };

#define MAX6675_HEAT_INTERVAL 250UL

Expand Down Expand Up @@ -2144,33 +2150,41 @@ void Temperature::disable_all_heaters() {
WRITE_MAX6675(HIGH); // disable TT_MAX6675

if (max6675_temp & MAX6675_ERROR_MASK) {
SERIAL_ERROR_START();
SERIAL_ECHOPGM("Temp measurement error! ");
#if MAX6675_ERROR_MASK == 7
SERIAL_ECHOPGM("MAX31855 ");
if (max6675_temp & 1)
SERIAL_ECHOLNPGM("Open Circuit");
else if (max6675_temp & 2)
SERIAL_ECHOLNPGM("Short to GND");
else if (max6675_temp & 4)
SERIAL_ECHOLNPGM("Short to VCC");
#else
SERIAL_ECHOLNPGM("MAX6675");
#endif

// Thermocouple open
max6675_temp = 4 * (
#if COUNT_6675 > 1
hindex ? HEATER_1_MAX6675_TMAX : HEATER_0_MAX6675_TMAX
#elif ENABLED(HEATER_1_USES_MAX6675)
HEATER_1_MAX6675_TMAX
max6675_errors[hindex] += 1;
if (max6675_errors[hindex] > THERMOCOUPLE_MAX_ERRORS) {
SERIAL_ERROR_START();
SERIAL_ECHOPGM("Temp measurement error! ");
#if MAX6675_ERROR_MASK == 7
SERIAL_ECHOPGM("MAX31855 ");
if (max6675_temp & 1)
SERIAL_ECHOLNPGM("Open Circuit");
else if (max6675_temp & 2)
SERIAL_ECHOLNPGM("Short to GND");
else if (max6675_temp & 4)
SERIAL_ECHOLNPGM("Short to VCC");
#else
HEATER_0_MAX6675_TMAX
SERIAL_ECHOLNPGM("MAX6675");
#endif
);

// Thermocouple open
max6675_temp = 4 * (
#if COUNT_6675 > 1
hindex ? HEATER_1_MAX6675_TMAX : HEATER_0_MAX6675_TMAX
#elif ENABLED(HEATER_1_USES_MAX6675)
HEATER_1_MAX6675_TMAX
#else
HEATER_0_MAX6675_TMAX
#endif
);
}
else {
max6675_temp >>= MAX6675_DISCARD_BITS;
}
}
else
else {
max6675_temp >>= MAX6675_DISCARD_BITS;
max6675_errors[hindex] = 0;
}

#if ENABLED(MAX6675_IS_MAX31855)
if (max6675_temp & 0x00002000) max6675_temp |= 0xFFFFC000; // Support negative temperature
Expand Down