From a866a758cc0ac671363fdce462dd967e488aa4e4 Mon Sep 17 00:00:00 2001
From: Jason Smith <jason.inet@gmail.com>
Date: Sun, 11 Oct 2020 22:40:39 -0700
Subject: [PATCH] Allow MAX31865 resistance values configuration (#19695)
---
Marlin/Configuration.h | 6 ++++++
Marlin/src/inc/SanityCheck.h | 4 ++++
Marlin/src/module/temperature.cpp | 4 ++--
3 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/Marlin/Configuration.h b/Marlin/Configuration.h
index ec8b162cd64..59f2be18c66 100644
--- a/Marlin/Configuration.h
+++ b/Marlin/Configuration.h
@@ -432,6 +432,12 @@
#define DUMMY_THERMISTOR_998_VALUE 25
#define DUMMY_THERMISTOR_999_VALUE 100
+// Resistor values when using a MAX31865 (sensor -5)
+// Sensor value is typically 100 (PT100) or 1000 (PT1000)
+// Calibration value is typically 430 ohm for AdaFruit PT100 modules and 4300 ohm for AdaFruit PT1000 modules.
+//#define MAX31865_SENSOR_OHMS 100
+//#define MAX31865_CALIBRATION_OHMS 430
+
// Use temp sensor 1 as a redundant sensor with sensor 0. If the readings
// from the two sensors differ too much the print will be aborted.
//#define TEMP_SENSOR_1_AS_REDUNDANT
diff --git a/Marlin/src/inc/SanityCheck.h b/Marlin/src/inc/SanityCheck.h
index c3708c26765..59a74411ef7 100644
--- a/Marlin/src/inc/SanityCheck.h
+++ b/Marlin/src/inc/SanityCheck.h
@@ -1845,6 +1845,10 @@ static_assert(hbm[Z_AXIS] >= 0, "HOMING_BUMP_MM.Z must be greater than or equal
#error "TEMP_SENSOR_1 is required with TEMP_SENSOR_1_AS_REDUNDANT."
#endif
+#if ENABLED(MAX6675_IS_MAX31865) && (!defined(MAX31865_SENSOR_OHMS) || !defined(MAX31865_CALIBRATION_OHMS))
+ #error "MAX31865_SENSOR_OHMS and MAX31865_CALIBRATION_OHMS must be set in Configuration.h when using a MAX31865 temperature sensor."
+#endif
+
/**
* Test Heater, Temp Sensor, and Extruder Pins
*/
diff --git a/Marlin/src/module/temperature.cpp b/Marlin/src/module/temperature.cpp
index f8ff972f803..9ecbb7c766f 100644
--- a/Marlin/src/module/temperature.cpp
+++ b/Marlin/src/module/temperature.cpp
@@ -1461,7 +1461,7 @@ void Temperature::manage_heater() {
#elif ENABLED(HEATER_0_USES_MAX6675)
return (
#if ENABLED(MAX6675_IS_MAX31865)
- max31865.temperature(100, 400) // 100 ohms = PT100 resistance. 400 ohms = calibration resistor
+ max31865.temperature(MAX31865_SENSOR_OHMS, MAX31865_CALIBRATION_OHMS)
#else
raw * 0.25
#endif
@@ -2236,7 +2236,7 @@ void Temperature::disable_all_heaters() {
next_max6675_ms[hindex] = ms + MAX6675_HEAT_INTERVAL;
#if ENABLED(MAX6675_IS_MAX31865)
- max6675_temp = int(max31865.temperature(100, 400)); // 100 ohms = PT100 resistance. 400 ohms = calibration resistor
+ max6675_temp = int(max31865.temperature(MAX31865_SENSOR_OHMS, MAX31865_CALIBRATION_OHMS));
#endif
//