Use RTD for MAX31865 reading (MarlinFirmware#20188)

dpreed · Feb 5, 2021 · 72ae6ae · 72ae6ae
1 parent 192a3ec
commit 72ae6ae
Showing 1 changed file with 4 additions and 4 deletions.
diff --git a/Marlin/src/module/temperature.cpp b/Marlin/src/module/temperature.cpp
@@ -2248,10 +2248,7 @@ void Temperature::disable_all_heaters() {
 
  #if HAS_MAX31865
  Adafruit_MAX31865 &maxref = MAX6675_SEL(max31865_0, max31865_1);
- max6675_temp = int(maxref.temperature(
- MAX6675_SEL(MAX31865_SENSOR_OHMS_0, MAX31865_SENSOR_OHMS_1),
- MAX6675_SEL(MAX31865_CALIBRATION_OHMS_0, MAX31865_CALIBRATION_OHMS_1)
- ));
+ const uint16_t max31865_ohms = (uint32_t(maxref.readRTD()) * MAX6675_SEL(MAX31865_CALIBRATION_OHMS_0, MAX31865_CALIBRATION_OHMS_1)) >> 16;
  #endif
 
  //
@@ -2325,6 +2322,9 @@ void Temperature::disable_all_heaters() {
  if (max6675_temp & 0x00002000) max6675_temp |= 0xFFFFC000; // Support negative temperature
  #endif
 
+ // Return the RTD resistance for MAX31865 for display in SHOW_TEMP_ADC_VALUES
+ TERN_(HAS_MAX31865, max6675_temp = max31865_ohms);
+
  MAX6675_TEMP(hindex) = max6675_temp;
 
  return int(max6675_temp);