useful content from Move ETB control to a thread #1374

firmware/controllers/actuators/electronic_throttle.cpp

@@ -387,6 +387,11 @@ void EtbController::update(efitick_t nowNt) {
 }
 
 #if !EFI_UNIT_TEST
+/**
+ * Things running on a timer (instead of a thread) don't participate it the RTOS's thread priority system,
+ * and operate essentially "first come first serve", which risks starvation.
+ * Since ETB is a safety critical device, we need the hard RTOS guarantee that it will be scheduled over other less important tasks.
+ */
 #include "periodic_thread_controller.h"
 struct EtbImpl final : public EtbController, public PeriodicController<512> {
 	EtbImpl() : PeriodicController("ETB", NORMALPRIO + 3, ETB_LOOP_FREQUENCY) {}

firmware/controllers/actuators/electronic_throttle.h

@@ -7,7 +7,12 @@
 
 #pragma once
 
-// https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem
+/**
+ * Hard code ETB update speed.
+ * Since this is a safety critical system with no real reason for a user to ever need to change the update rate,
+ * it's locked to 500hz, along with the ADC.
+ * https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem
+ */
 #define ETB_LOOP_FREQUENCY 500
 #define DEFAULT_ETB_PWM_FREQUENCY 800