🐛 Fix dual MAX31865 initialization issues (MarlinFirmware#23496)

Marlin/Configuration_adv.h

@@ -138,24 +138,21 @@
 #endif
 
 /**
- * Configuration options for MAX Thermocouples (-2, -3, -5).
- *   FORCE_HW_SPI:   Ignore SCK/MOSI/MISO pins and just use the CS pin & default SPI bus.
- *   MAX31865_WIRES: Set the number of wires for the probe connected to a MAX31865 board, 2-4. Default: 2
- *   MAX31865_50HZ:  Enable 50Hz filter instead of the default 60Hz.
- *   MAX31865_USE_READ_ERROR_DETECTION: Detects random read errors from value spikes (a 20°C difference in less than 1sec)
- *   MAX31865_USE_AUTO_MODE: Faster and more frequent reads than 1-shot, but bias voltage always on, slightly affecting RTD temperature.
- *   MAX31865_MIN_SAMPLING_TIME_MSEC: in 1-shot mode, the minimum time between subsequent reads. This reduces the effect of bias voltage by leaving the sensor unpowered for longer intervals.
- *   MAX31865_WIRE_OHMS: In 2-wire configurations, manually set the wire resistance for more accurate readings
+ * Thermocouple Options — for MAX6675 (-2), MAX31855 (-3), and MAX31865 (-5).
  */
-//#define TEMP_SENSOR_FORCE_HW_SPI
-//#define MAX31865_SENSOR_WIRES_0 2
+//#define TEMP_SENSOR_FORCE_HW_SPI                // Ignore SCK/MOSI/MISO pins; use CS and the default SPI bus.
+//#define MAX31865_SENSOR_WIRES_0 2               // (2-4) Number of wires for the probe connected to a MAX31865 board.
 //#define MAX31865_SENSOR_WIRES_1 2
-//#define MAX31865_50HZ_FILTER
-//#define MAX31865_USE_READ_ERROR_DETECTION
-//#define MAX31865_USE_AUTO_MODE
-//#define MAX31865_MIN_SAMPLING_TIME_MSEC 100
-//#define MAX31865_WIRE_OHMS_0 0.0f
-//#define MAX31865_WIRE_OHMS_1 0.0f
+
+//#define MAX31865_50HZ_FILTER                    // Use a 50Hz filter instead of the default 60Hz.
+//#define MAX31865_USE_READ_ERROR_DETECTION       // Treat value spikes (20°C delta in under 1s) as read errors.
+
+//#define MAX31865_USE_AUTO_MODE                  // Read faster and more often than 1-shot; bias voltage always on; slight effect on RTD temperature.
+//#define MAX31865_MIN_SAMPLING_TIME_MSEC     100 // (ms) 1-shot: minimum read interval. Reduces bias voltage effects by leaving sensor unpowered for longer intervals.
+//#define MAX31865_IGNORE_INITIAL_FAULTY_READS 10 // Ignore some read faults (keeping the temperature reading) to work around a possible issue (#23439).
+
+//#define MAX31865_WIRE_OHMS_0              0.95f // For 2-wire, set the wire resistances for more accurate readings.
+//#define MAX31865_WIRE_OHMS_1              0.0f
 
 /**
  * Hephestos 2 24V heated bed upgrade kit.

Marlin/src/HAL/shared/Delay.h

@@ -166,6 +166,8 @@ void calibrate_delay_loop();
   // Delay in microseconds
   #define DELAY_US(x) DELAY_CYCLES((x) * ((F_CPU) / 1000000UL))
 
+  #define DELAY_CYCLES_VAR DELAY_CYCLES
+
 #elif defined(ESP32) || defined(__PLAT_LINUX__) || defined(__PLAT_NATIVE_SIM__)
 
   // DELAY_CYCLES specified inside platform