mimxrt/machine_timer: Use soft-timer implementation for machine.Timer.

This releases the hardware timers for other tasks, which need a higher
resolution and faster response.  And it is less port-specific code.

Author: robert-hh

docs/mimxrt/quickref.rst

@@ -56,21 +56,18 @@ Use the :mod:`time <time>` module::
 Timers
 ------
 
-The i.MXRT port has three hardware timers. Use the :ref:`machine.Timer <machine.Timer>` class
-with a timer ID from 0 to 2 (inclusive)::
+The i.MXRT port supports virtual Timers. Example of usage::
 
     from machine import Timer
 
-    tim0 = Timer(0)
+    tim0 = Timer(-1)
     tim0.init(period=5000, mode=Timer.ONE_SHOT, callback=lambda t:print(0))
 
-    tim1 = Timer(1)
+    tim1 = Timer(-1)
     tim1.init(period=2000, mode=Timer.PERIODIC, callback=lambda t:print(1))
 
 The period is in milliseconds.
 
-Virtual timers are not currently supported on this port.
-
 .. _mimxrt_Pins_and_GPIO:
 
 Pins and GPIO

ports/mimxrt/Makefile

@@ -193,6 +193,7 @@ SHARED_SRC_C += \
 	shared/runtime/interrupt_char.c \
 	shared/runtime/mpirq.c \
 	shared/runtime/pyexec.c \
+	shared/runtime/softtimer.c \
 	shared/runtime/stdout_helpers.c \
 	shared/runtime/sys_stdio_mphal.c \
 	shared/timeutils/timeutils.c \

ports/mimxrt/board_init.c

@@ -89,9 +89,6 @@ void board_init(void) {
     // ADC
     machine_adc_init();
 
-    // PIT
-    machine_timer_init_PIT();
-
     // SDCard
     #if MICROPY_PY_MACHINE_SDCARD
     machine_sdcard_init0();

ports/mimxrt/machine_timer.c

@@ -26,66 +26,24 @@
  */
 
 #include "py/runtime.h"
-#include "py/mperrno.h"
 #include "py/mphal.h"
-#include "fsl_pit.h"
-#include "modmachine.h"
-#include CLOCK_CONFIG_H
-
-#define TIMER_MODE_ONE_SHOT (0)
-#define TIMER_MODE_PERIODIC (1)
-#define TIMER_MIN_PERIOD 1
-
-#define alarm_callback PIT_IRQHandler
-#define PIT_IRQ_ID PIT_IRQn
-
-typedef struct _machine_timer_obj_t {
-    mp_obj_base_t base;
-    int8_t id;
-    int8_t channel;
-    uint32_t mode;
-    uint32_t tick_hz;
-    uint32_t delta_us; // for periodic mode
-    mp_obj_t callback;
-} machine_timer_obj_t;
-
-static const int8_t channel_no[MICROPY_HW_PIT_NUM_CHANNELS] = {0, 2, 3}; // no channel 1
-static pit_config_t pit_config;
-
-// This is the interrupt handler
-// To tell which channel fired one has to poll the flags
-void alarm_callback(void) {
-    for (uint8_t index = 0; index < MICROPY_HW_PIT_NUM_CHANNELS; index++) {
-        uint32_t flag;
-        machine_timer_obj_t *self = MP_STATE_PORT(timer_table)[index];
-        if (self != NULL) {
-            flag = PIT_GetStatusFlags(PIT, self->channel);
-            if (flag & kPIT_TimerFlag) { // channel fired
-                PIT_ClearStatusFlags(PIT, self->channel, kPIT_TimerFlag);
-                __DSB();
-
-                mp_sched_schedule(self->callback, MP_OBJ_FROM_PTR(self));
-
-                if (self->mode == TIMER_MODE_ONE_SHOT) {
-                    PIT_StopTimer(PIT, self->channel);
-                }
-            }
-        }
-    }
-}
+#include "shared/runtime/softtimer.h"
+
+typedef soft_timer_entry_t machine_timer_obj_t;
+
+const mp_obj_type_t machine_timer_type;
 
 STATIC void machine_timer_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     machine_timer_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    qstr mode = self->mode == TIMER_MODE_ONE_SHOT ? MP_QSTR_ONE_SHOT : MP_QSTR_PERIODIC;
-    mp_printf(print, "Timer(channel=%d, mode=%q, period=%d, tick_hz=%d)",
-        self->id, mode, self->delta_us / self->tick_hz, self->tick_hz);
+    qstr mode = self->mode == SOFT_TIMER_MODE_ONE_SHOT ? MP_QSTR_ONE_SHOT : MP_QSTR_PERIODIC;
+    mp_printf(print, "Timer(mode=%q, period=%u)", mode, self->delta_ms);
 }
 
 STATIC mp_obj_t machine_timer_init_helper(machine_timer_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_mode, ARG_callback, ARG_period, ARG_tick_hz, ARG_freq, };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_mode,         MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = TIMER_MODE_PERIODIC} },
-        { MP_QSTR_callback,     MP_ARG_REQUIRED | MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_mode,         MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = SOFT_TIMER_MODE_PERIODIC} },
+        { MP_QSTR_callback,     MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
         { MP_QSTR_period,       MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0xffffffff} },
         { MP_QSTR_tick_hz,      MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 1000} },
         { MP_QSTR_freq,         MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
@@ -96,67 +54,56 @@ STATIC mp_obj_t machine_timer_init_helper(machine_timer_obj_t *self, size_t n_ar
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
     self->mode = args[ARG_mode].u_int;
+
+    uint64_t delta_ms = self->delta_ms;
     if (args[ARG_freq].u_obj != mp_const_none) {
         // Frequency specified in Hz
         #if MICROPY_PY_BUILTINS_FLOAT
-        self->delta_us = (uint32_t)(MICROPY_FLOAT_CONST(1000000.0) / mp_obj_get_float(args[ARG_freq].u_obj));
+        delta_ms = (uint32_t)(MICROPY_FLOAT_CONST(1000.0) / mp_obj_get_float(args[ARG_freq].u_obj));
         #else
-        self->delta_us = 1000000 / mp_obj_get_int(args[ARG_freq].u_obj);
+        delta_ms = 1000 / mp_obj_get_int(args[ARG_freq].u_obj);
         #endif
-    } else {
+    } else if (args[ARG_period].u_int != 0xffffffff) {
         // Period specified
-        self->tick_hz = args[ARG_tick_hz].u_int;
-        self->delta_us = (uint64_t)args[ARG_period].u_int * 1000000 / self->tick_hz;
-    }
-    if (self->delta_us < TIMER_MIN_PERIOD) {
-        self->delta_us = TIMER_MIN_PERIOD;
+        delta_ms = (uint64_t)args[ARG_period].u_int * 1000 / args[ARG_tick_hz].u_int;
     }
 
-    self->callback = args[ARG_callback].u_obj;
-
-    // Set timer period for channel id
-    PIT_SetTimerPeriod(PIT, self->channel, USEC_TO_COUNT(self->delta_us, BOARD_BOOTCLOCKRUN_IPG_CLK_ROOT));
-
-    // Enable timer interrupts for the channel
-    PIT_EnableInterrupts(PIT, self->channel, kPIT_TimerInterruptEnable);
+    if (delta_ms < 1) {
+        delta_ms = 1;
+    } else if (delta_ms >= 0x40000000) {
+        mp_raise_ValueError(MP_ERROR_TEXT("period too large"));
+    }
+    self->delta_ms = (uint32_t)delta_ms;
 
-    // Enable at the NVIC
-    EnableIRQ(PIT_IRQ_ID);
+    if (args[ARG_callback].u_obj != MP_OBJ_NULL) {
+        self->py_callback = args[ARG_callback].u_obj;
+    }
 
-    // Start channel 0
-    PIT_StartTimer(PIT, self->channel);
+    if (self->py_callback != mp_const_none) {
+        soft_timer_insert(self, self->delta_ms);
+    }
 
     return mp_const_none;
 }
 
 STATIC mp_obj_t machine_timer_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
-    machine_timer_obj_t *self;
-
-    // Get timer id in the range of 0..2
-    mp_int_t id = 0;
+    machine_timer_obj_t *self = m_new_obj(machine_timer_obj_t);
+    self->pairheap.base.type = &machine_timer_type;
+    self->flags = SOFT_TIMER_FLAG_PY_CALLBACK | SOFT_TIMER_FLAG_GC_ALLOCATED;
+    self->delta_ms = 1000;
+    self->py_callback = mp_const_none;
+
+    // Get timer id (only soft timer (-1) supported at the moment)
+    mp_int_t id = -1;
     if (n_args > 0) {
         id = mp_obj_get_int(args[0]);
         --n_args;
         ++args;
     }
-    if (id < 0 || id >= MICROPY_HW_PIT_NUM_CHANNELS) {
-        mp_raise_ValueError(MP_ERROR_TEXT("Timer does not exist"));
+    if (id != -1) {
+        mp_raise_ValueError(MP_ERROR_TEXT("Timer doesn't exist"));
     }
 
-    // check, if a timer exists at that channel and stop it first
-    if (MP_STATE_PORT(timer_table)[id] != NULL) {
-        PIT_StopTimer(PIT, channel_no[id]);
-        self = MP_STATE_PORT(timer_table)[id];
-    } else {
-        self = m_new_obj_with_finaliser(machine_timer_obj_t);
-        self->base.type = &machine_timer_type;
-        MP_STATE_PORT(timer_table)[id] = self;
-    }
-
-    // Set initial values
-    self->id = id;
-    self->channel = channel_no[id];
-
     if (n_args > 0 || n_kw > 0) {
         // Start the timer
         mp_map_t kw_args;
@@ -167,47 +114,26 @@ STATIC mp_obj_t machine_timer_make_new(const mp_obj_type_t *type, size_t n_args,
     return MP_OBJ_FROM_PTR(self);
 }
 
-STATIC mp_obj_t machine_timer___del__(mp_obj_t self_in) {
-    machine_timer_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    PIT_StopTimer(PIT, self->channel);
-    MP_STATE_PORT(timer_table)[self->id] = NULL;
-    return mp_const_none;
-}
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_timer___del___obj, machine_timer___del__);
-
 STATIC mp_obj_t machine_timer_init(size_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
     machine_timer_obj_t *self = MP_OBJ_TO_PTR(args[0]);
-    PIT_StopTimer(PIT, self->channel);
+    soft_timer_remove(self);
     return machine_timer_init_helper(self, n_args - 1, args + 1, kw_args);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(machine_timer_init_obj, 1, machine_timer_init);
 
 STATIC mp_obj_t machine_timer_deinit(mp_obj_t self_in) {
     machine_timer_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    PIT_StopTimer(PIT, self->channel);
+    soft_timer_remove(self);
     return mp_const_none;
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_timer_deinit_obj, machine_timer_deinit);
 
-// Initialize clock an first config
-void machine_timer_init_PIT(void) {
-    // PIT timer
-    // Enable clock gate for GPIO1
-    CLOCK_EnableClock(kCLOCK_Gpio1); // ?
-    // Set PERCLK_CLK divider to 1
-    CLOCK_SetDiv(kCLOCK_PerclkDiv, 0U);
-
-    PIT_GetDefaultConfig(&pit_config);
-    PIT_Init(PIT, &pit_config);
-}
-
 STATIC const mp_rom_map_elem_t machine_timer_locals_dict_table[] = {
-    { MP_ROM_QSTR(MP_QSTR___del__), MP_ROM_PTR(&machine_timer___del___obj) },
     { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&machine_timer_init_obj) },
     { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&machine_timer_deinit_obj) },
 
-    { MP_ROM_QSTR(MP_QSTR_ONE_SHOT), MP_ROM_INT(TIMER_MODE_ONE_SHOT) },
-    { MP_ROM_QSTR(MP_QSTR_PERIODIC), MP_ROM_INT(TIMER_MODE_PERIODIC) },
+    { MP_ROM_QSTR(MP_QSTR_ONE_SHOT), MP_ROM_INT(SOFT_TIMER_MODE_ONE_SHOT) },
+    { MP_ROM_QSTR(MP_QSTR_PERIODIC), MP_ROM_INT(SOFT_TIMER_MODE_PERIODIC) },
 };
 STATIC MP_DEFINE_CONST_DICT(machine_timer_locals_dict, machine_timer_locals_dict_table);
 
@@ -219,5 +145,3 @@ MP_DEFINE_CONST_OBJ_TYPE(
     print, machine_timer_print,
     locals_dict, &machine_timer_locals_dict
     );
-
-MP_REGISTER_ROOT_POINTER(struct _machine_timer_obj_t *timer_table[MICROPY_HW_PIT_NUM_CHANNELS]);

ports/mimxrt/main.c

@@ -33,6 +33,7 @@
 #include "shared/readline/readline.h"
 #include "shared/runtime/gchelper.h"
 #include "shared/runtime/pyexec.h"
+#include "shared/runtime/softtimer.h"
 #include "ticks.h"
 #include "tusb.h"
 #include "led.h"
@@ -120,6 +121,7 @@ int main(void) {
         mod_network_deinit();
         #endif
         machine_pwm_deinit_all();
+        soft_timer_deinit();
         gc_sweep_all();
         mp_deinit();
     }

ports/mimxrt/mphalport.h

@@ -38,6 +38,10 @@
 #define MP_HAL_PIN_FMT                  "%q"
 extern ringbuf_t stdin_ringbuf;
 
+// Define an alias fo systick_ms, because the shared softtimer.c uses
+// the symbol uwTick for the systick ms counter.
+#define uwTick systick_ms
+
 #define mp_hal_pin_obj_t const machine_pin_obj_t *
 #define mp_hal_get_pin_obj(o)   pin_find(o)
 #define mp_hal_pin_name(p)      ((p)->name)

ports/mimxrt/systick.c

@@ -28,6 +28,9 @@
 #include "py/mphal.h"
 #include "systick.h"
 
+#include "pendsv.h"
+#include "shared/runtime/softtimer.h"
+
 volatile uint32_t systick_ms = 0;
 
 systick_dispatch_t systick_dispatch_table[SYSTICK_DISPATCH_NUM_SLOTS];
@@ -44,6 +47,10 @@ void SysTick_Handler(void) {
     if (f != NULL) {
         f(uw_tick);
     }
+
+    if (soft_timer_next == uw_tick) {
+        pendsv_schedule_dispatch(PENDSV_DISPATCH_SOFT_TIMER, soft_timer_handler);
+    }
 }
 
 bool systick_has_passed(uint32_t start_tick, uint32_t delay_ms) {