Hardware timer support

core/include/esp/timer.h

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+/** esp/timer.h
+ *
+ * Timer (FRC1 & FRC2) functions.
+ *
+ * Part of esp-open-rtos
+ * Copyright (C) 2015 Superhouse Automation Pty Ltd
+ * BSD Licensed as described in the file LICENSE
+ */
+#ifndef _ESP_TIMER_H
+#define _ESP_TIMER_H
+
+#include <stdbool.h>
+#include <xtensa_interrupts.h>
+#include "esp/registers.h"
+#include "esp/cpu.h"
+
+typedef enum {
+    TIMER_FRC1,
+    TIMER_FRC2,
+} timer_frc_t;
+
+/* Return current count value for timer. */
+INLINED uint32_t timer_get_count(const timer_frc_t frc);
+
+/* Return current load value for timer. */
+INLINED uint32_t timer_get_load(const timer_frc_t frc);
+
+/* Write load value for timer. */
+INLINED void timer_set_load(const timer_frc_t frc, const uint32_t load);
+
+/* Returns maximum load value for timer. */
+INLINED uint32_t timer_max_load(const timer_frc_t frc);
+
+typedef enum {
+    TIMER_DIV1,
+    TIMER_DIV16,
+    TIMER_DIV256,
+} timer_div_t;
+
+/* Set the timer divider value */
+INLINED void timer_set_divider(const timer_frc_t frc, const timer_div_t div);
+
+/* Enable or disable timer interrupts
+
+   This both sets the xtensa interrupt mask and writes to the DPORT register
+   that allows timer interrupts.
+*/
+INLINED void timer_set_interrupts(const timer_frc_t frc, bool enable);
+
+/* Turn the timer on or off */
+INLINED void timer_set_run(const timer_frc_t frc, const bool run);
+
+/* Get the run state of the timer (on or off) */
+INLINED bool timer_get_run(const timer_frc_t frc);
+
+/* Set timer auto-reload on or off */
+INLINED void timer_set_reload(const timer_frc_t frc, const bool reload);
+
+/* Get the auto-reload state of the timer (on or off) */
+INLINED bool timer_get_reload(const timer_frc_t frc);
+
+/* Return a suitable timer divider for the specified frequency,
+   or -1 if none is found.
+ */
+INLINED timer_div_t timer_freq_to_div(uint32_t freq);
+
+/* Return the number of timer counts to achieve the specified
+ * frequency with the specified divisor.
+ *
+ * frc parameter is used to check out-of-range values for timer size.
+ *
+ * Returns 0 if the given freq/divisor combo cannot be achieved.
+ *
+ * Compile-time evaluates if all arguments are available at compile time.
+ */
+INLINED uint32_t timer_freq_to_count(const timer_frc_t frc, uint32_t freq, const timer_div_t div);
+
+/* Return a suitable timer divider for the specified duration in
+   microseconds or -1 if none is found.
+ */
+INLINED timer_div_t timer_time_to_div(uint32_t us);
+
+/* Return the number of timer counts for the specified timer duration
+ * in microseconds, when using the specified divisor.
+ *
+ * frc paraemter is used to check out-of-range values for timer size.
+ *
+ * Returns 0 if the given time/divisor combo cannot be achieved.
+ *
+ * Compile-time evaluates if all arguments are available at compile time.
+ */
+INLINED uint32_t timer_time_to_count(const timer_frc_t frc, uint32_t us, const timer_div_t div);
+
+/* Set a target timer interrupt frequency in Hz.
+
+   For FRC1 this sets the timer load value and enables autoreload so
+   the interrupt will fire regularly with the target frequency.
+
+   For FRC2 this sets the timer match value so the next interrupt
+   comes in line with the target frequency. However this won't repeat
+   automatically, you have to call timer_set_frequency again when the
+   timer interrupt runs.
+
+   Will change the timer divisor value to suit the target frequency.
+
+   Does not start/stop the timer, you have to do this manually via
+   timer_set_run.
+
+   Returns true on success, false if given frequency could not be set.
+
+   Compile-time evaluates to simple register writes if all arguments
+   are available at compile time.
+*/
+INLINED bool timer_set_frequency(const timer_frc_t frc, uint32_t freq);
+
+/* Sets the timer for a oneshot interrupt in 'us' microseconds.
+
+   Will change the timer divisor value to suit the target time.
+
+   Does not change the autoreload setting.
+
+   For FRC2 this sets the timer match value relative to the current
+   load value.
+
+   Note that for a true "one shot" timeout with FRC1 then you need to
+   also disable FRC1 in the timer interrupt handler by calling
+   timer_set_run(TIMER_FRC1, false);
+
+   Returns true if the timeout was successfully set.
+
+   Compile-time evaluates to simple register writes if all arguments
+   are available at compile time.
+*/
+INLINED bool timer_set_timeout(const timer_frc_t frc, uint32_t us);
+
+#include "timer_private.h"
+
+#endif