Checked in missing file

FluidNC/include/Driver/step_engine.h

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+// Copyright (c) 2024 -  Mitch Bradley
+// Use of this source code is governed by a GPLv3 license that can be found in the LICENSE file.
+
+// Interface between Stepping.cpp and low-level stepping engine drivers
+// This is in C instead of C++ to make it easy to force the relevant pieces
+// to be in RAM or IRAM, thus avoiding ESP32 problems with accessing FLASH
+// from interrupt service routines.
+
+#pragma once
+
+#include <stdint.h>
+
+typedef struct step_engine {
+    const char* name;
+
+    // Prepare the engine for use
+    // The return value is the actual pulse delay according to the
+    // characteristics of the engine.
+    uint32_t (*init)(uint32_t dir_delay_us, uint32_t pulse_delay_us);
+
+    // Setup the step pin, returning a number to identify it.
+    // In many cases, the return value is the same as pin, but some step
+    // engines might allocate a surrogate object and return its ID
+    int (*init_step_pin)(int pin, int inverted);
+
+    // Set the state of the direction pin to level
+    void (*set_dir_pin)(int pin, int level);
+
+    // Commit all of the direction pin changes and wait for dir_delay_us
+    // if necessary
+    void (*finish_dir)();
+
+    // Set the state of the step pin to level
+    void (*start_step)();
+
+    // Set the state of the step pin to level
+    void (*set_step_pin)(int pin, int level);
+
+    // Commit all of the direction pin changes and either wait for pulse_delay_us
+    // or arrange for start_unstep to do it
+    void (*finish_step)();
+
+    // Wait for pulse_delay_us if necessary
+    // If the return value is true, Stepping.cpp will skip the rest of the
+    // the unstep process
+    int (*start_unstep)();
+
+    // Commit all changes (deassertions) of step pins
+    void (*finish_unstep)();
+
+    // The maximum step rate for this engine as a function of dir_delay_us,
+    // pulse_delay_us, and other characteristics of this stepping engine
+    uint32_t (*max_pulses_per_sec)();
+
+    // Link to next engine in the list of registered stepping engines
+    struct step_engine* link;
+} step_engine_t;
+
+// Linked list of registered step engines
+extern step_engine_t* step_engines;
+
+// clang-format off
+#define REGISTER_STEP_ENGINE(name, engine)                       \
+    __attribute__((constructor)) void __register_##name(void) {  \
+        (engine)->link = step_engines;                           \
+        step_engines = engine;                                   \
+    }