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Extend measuring range of thermocouple for MAX31855 #5071

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thinkyhead merged 1 commit into from Oct 24, 2016
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Extend measuring range of thermocouple for MAX31855 #5071

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4 changes: 4 additions & 0 deletions Marlin/Conditionals_post.h
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Original file line number Diff line number Diff line change
Expand Up @@ -222,8 +222,12 @@
#if TEMP_SENSOR_0 == -3
#define HEATER_0_USES_MAX6675
#define MAX6675_IS_MAX31855
#define MAX6675_TMIN -270
#define MAX6675_TMAX 1800
#elif TEMP_SENSOR_0 == -2
#define HEATER_0_USES_MAX6675
#define MAX6675_TMIN 0
#define MAX6675_TMAX 1024
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@ghost ghost Oct 23, 2016

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Is it better that these are written in temperature.h?

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@thinkyhead thinkyhead Oct 24, 2016

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No, these are fine here. Thank you for asking.

#elif TEMP_SENSOR_0 == -1
#define HEATER_0_USES_AD595
#elif TEMP_SENSOR_0 == 0
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10 changes: 7 additions & 3 deletions Marlin/temperature.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -669,8 +669,8 @@ void Temperature::manage_heater() {
updateTemperaturesFromRawValues(); // also resets the watchdog

#if ENABLED(HEATER_0_USES_MAX6675)
if (current_temperature[0] > min(HEATER_0_MAXTEMP, 1023)) max_temp_error(0);
if (current_temperature[0] < max(HEATER_0_MINTEMP, 0.01)) min_temp_error(0);
if (current_temperature[0] > min(HEATER_0_MAXTEMP, MAX6675_TMAX - 1)) max_temp_error(0);
if (current_temperature[0] < max(HEATER_0_MINTEMP, MAX6675_TMIN + 0.01)) min_temp_error(0);
#endif

#if (ENABLED(THERMAL_PROTECTION_HOTENDS) && WATCH_TEMP_PERIOD > 0) || (ENABLED(THERMAL_PROTECTION_BED) && WATCH_BED_TEMP_PERIOD > 0) || DISABLED(PIDTEMPBED) || HAS_AUTO_FAN
Expand Down Expand Up @@ -1355,10 +1355,14 @@ void Temperature::disable_all_heaters() {
#else
SERIAL_ERRORLNPGM("MAX6675");
#endif
max6675_temp = 4000; // thermocouple open
max6675_temp = MAX6675_TMAX * 4; // thermocouple open
}
else
max6675_temp >>= MAX6675_DISCARD_BITS;
#if ENABLED(MAX6675_IS_MAX31855)
// Support negative temperature
if (max6675_temp & 0x00002000) max6675_temp |= 0xffffc000;
#endif

return (int)max6675_temp;
}
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