✨ Teensy 4 hardware PWM for laser/spindle/fan (#27608)

Marlin/src/HAL/TEENSY40_41/HAL.cpp

@@ -202,18 +202,13 @@ uint16_t MarlinHAL::adc_value() {
 // Free Memory Accessor
 // ------------------------
 
-#define __bss_end _ebss
-
 extern "C" {
-  extern char __bss_end;
-  extern char __heap_start;
-  extern void* __brkval;
+  // Reference for Teensy 4.x: https://forum.pjrc.com/index.php?threads/how-to-display-free-ram.33443/#post-275013
+  extern unsigned long _heap_end;
+  extern char *__brkval;
 
-  // Doesn't work on Teensy 4.x
   uint32_t freeMemory() {
-    uint32_t free_memory;
-    free_memory = ((uint32_t)&free_memory) - (((uint32_t)__brkval) ?: ((uint32_t)&__bss_end));
-    return free_memory;
+    return (char *)&_heap_end - __brkval;
   }
 }
 

Marlin/src/HAL/TEENSY40_41/HAL.h

@@ -61,6 +61,8 @@
 #undef PSTR
 #define PSTR(str) ({static const char *data = (str); &data[0];})
 
+#define HAL_CAN_SET_PWM_FREQ
+
 // ------------------------
 // Serial ports
 // ------------------------
@@ -221,11 +223,15 @@ public:
 
   /**
    * Set the PWM duty cycle for the pin to the given value.
-   * No option to invert the duty cycle [default = false]
-   * No option to change the scale of the provided value to enable finer PWM duty control [default = 255]
+   * Optionally invert the duty cycle [default = false]
+   * Optionally change the scale of the provided value to enable finer PWM duty control [default = 255]
    */
-  static void set_pwm_duty(const pin_t pin, const uint16_t v, const uint16_t=255, const bool=false) {
-    analogWrite(pin, v);
-  }
+  static void set_pwm_duty(const pin_t pin, const uint16_t v, const uint16_t v_size=255, const bool invert=false);
 
+  /**
+   * Set the PWM output frequency. This may affect multiple pins, though
+   * Teensy 4.x provides many timers affecting only a single pin.
+   * See: https://www.pjrc.com/teensy/td_pulse.html
+   */
+  static void set_pwm_frequency(const pin_t pin, const uint16_t f_desired);
 };

Marlin/src/HAL/TEENSY40_41/fast_pwm.cpp

@@ -0,0 +1,54 @@
+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (c) 2025 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (c) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifdef __IMXRT1062__
+
+#include "../../inc/MarlinConfig.h"
+
+#include "HAL.h"
+
+void MarlinHAL::set_pwm_duty(const pin_t pin, const uint16_t v, const uint16_t v_size /*=255*/, const bool invert) {
+
+  uint32_t bits = 1;
+  uint16_t value = _MIN(v, v_size);
+
+  if (invert) value = v_size - value;
+
+  // Choose scale as smallest power of 2 which holds v_size.
+  uint32_t scale = 1;
+  while (scale < v_size) {
+    bits++;
+    scale *= 2;
+  }
+
+  uint32_t scaled_val = scale * value / v_size;
+
+  uint32_t prior = analogWriteResolution(bits);
+  analogWrite(pin, scaled_val);
+  analogWriteResolution(prior);
+}
+
+void MarlinHAL::set_pwm_frequency(const pin_t pin, const uint16_t f_desired) {
+  analogWriteFrequency(pin, f_desired);
+}
+
+#endif // __IMXRT1062__

Marlin/src/HAL/TEENSY40_41/inc/SanityCheck.h

@@ -33,10 +33,6 @@
   #error "EMERGENCY_PARSER is not yet implemented for Teensy 4.0/4.1. Disable EMERGENCY_PARSER to continue."
 #endif
 
-#if ENABLED(FAST_PWM_FAN) || SPINDLE_LASER_FREQUENCY
-  #error "Features requiring Hardware PWM (FAST_PWM_FAN, SPINDLE_LASER_FREQUENCY) are not yet supported for Teensy 4.0/4.1."
-#endif
-
 #if HAS_TMC_SW_SERIAL
   #error "TMC220x Software Serial is not supported for Teensy 4.0/4.1."
 #endif
@@ -44,3 +40,19 @@
 #if ENABLED(POSTMORTEM_DEBUGGING)
   #error "POSTMORTEM_DEBUGGING is not yet supported for Teensy 4.0/4.1."
 #endif
+
+#if ENABLED(SERIAL_STATS_MAX_RX_QUEUED) || ENABLED(SERIAL_STATS_DROPPED_RX) || ENABLED(SERIAL_STATS_RX_FRAMING_ERRORS) || ENABLED(SERIAL_STATS_RX_BUFFER_OVERRUNS)
+  #error "SERIAL_STATS_* features not supported on Teensy 4.0/4.1."
+#endif
+
+#if ENABLED(BAUD_RATE_GCODE) && SERIAL_PORT_2 == -2
+  #error "BAUD_RATE_GCODE cannot be enabled when using the Ethernet serial port."
+#endif
+
+#if ENABLED(SPINDLE_LASER_USE_PWM) && !ENABLED(SILENCE_TEENSY_SPINDLE_LASER_WARNING)
+  #warning "SPINDLE_LASER_USE_PWM is untested on Teensy 4.0/4.1, see https://www.pjrc.com/teensy/td_pulse.html for details on frequencies, and resolution. #define SILENCE_TEENSY_SPINDLE_LASER_WARNING to silence warning."
+#endif
+
+#if ENABLED(FAST_PWM_FAN) && FAST_PWM_FAN_FREQUENCY == 1000U
+  #warning "FAST_PWM_FAN_FREQUENCY has been left as default, see https://www.pjrc.com/teensy/td_pulse.html and consider raising it to reduce noise."
+#endif

Marlin/src/gcode/calibrate/M100.cpp

@@ -60,7 +60,7 @@
 
 #define TEST_BYTE ((char) 0xE5)
 
-#if ANY(__AVR__, IS_32BIT_TEENSY)
+#if ANY(__AVR__, IS_32BIT_TEENSY) && !IS_TEENSY_40_41
 
   extern char __bss_end;
   char *end_bss = &__bss_end,