timer.c 19.4 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
/*
 * This file is part of the Micro Python project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2013, 2014 Damien P. George
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

27
28
29
30
31
32
33
34
35
36
37
38
#include <stdint.h>
#include <stdio.h>
#include <string.h>

#include <stm32f4xx_hal.h>
#include "usbd_cdc_msc_hid.h"
#include "usbd_cdc_interface.h"

#include "nlr.h"
#include "misc.h"
#include "mpconfig.h"
#include "qstr.h"
39
#include "gc.h"
40
41
42
43
44
#include "obj.h"
#include "runtime.h"
#include "timer.h"
#include "servo.h"

45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
/// \moduleref pyb
/// \class Timer - periodically call a function
///
/// Timers can be used for a great variety of tasks.  At the moment, only
/// the simplest case is implemented: that of calling a function periodically.
///
/// Each timer consists of a counter that counts up at a certain rate.  The rate
/// at which it counts is the peripheral clock frequency (in Hz) divided by the
/// timer prescaler.  When the counter reaches the timer period it triggers an
/// event, and the counter resets back to zero.  By using the callback method,
/// the timer event can call a Python function.
///
/// Example usage to toggle an LED at a fixed frequency:
///
///     tim = pyb.Timer(4)              # create a timer object using timer 4
///     tim.init(freq=2)                # trigger at 2Hz
///     tim.callback(lambda t:pyb.LED(1).toggle())
///
/// Further examples:
///
///     tim = pyb.Timer(4, freq=100)    # freq in Hz
///     tim = pyb.Timer(4, prescaler=1, period=100)
///     tim.counter()                   # get counter (can also set)
///     tim.prescaler(2)                # set prescaler (can also get)
///     tim.period(200)                 # set period (can also get)
///     tim.callback(lambda t: ...)     # set callback for update interrupt (t=tim instance)
///     tim.callback(None)              # clear callback
///
/// *Note:* Timer 3 is reserved for internal use.  Timer 5 controls
/// the servo driver, and Timer 6 is used for timed ADC/DAC reading/writing.
/// It is recommended to use the other timers in your programs.

77
78
79
80
// The timers can be used by multiple drivers, and need a common point for
// the interrupts to be dispatched, so they are all collected here.
//
// TIM3:
81
//  - flash storage controller, to flush the cache
82
83
84
85
86
//  - USB CDC interface, interval, to check for new data
//  - LED 4, PWM to set the LED intensity
//
// TIM5:
//  - servo controller, PWM
87
88
89
90
91
92
//
// TIM6:
//  - ADC, DAC for read_timed and write_timed

typedef struct _pyb_timer_obj_t {
    mp_obj_base_t base;
93
    mp_uint_t tim_id;
94
95
96
97
    mp_obj_t callback;
    TIM_HandleTypeDef tim;
    IRQn_Type irqn;
} pyb_timer_obj_t;
98
99
100

TIM_HandleTypeDef TIM3_Handle;
TIM_HandleTypeDef TIM5_Handle;
101
TIM_HandleTypeDef TIM6_Handle;
102

103
104
105
// Used to divide down TIM3 and periodically call the flash storage IRQ
static uint32_t tim3_counter = 0;

106
107
// Used to do callbacks to Python code on interrupt
STATIC pyb_timer_obj_t *pyb_timer_obj_all[14];
108
#define PYB_TIMER_OBJ_ALL_NUM MP_ARRAY_SIZE(pyb_timer_obj_all)
109

110
111
112
STATIC mp_obj_t pyb_timer_deinit(mp_obj_t self_in);
STATIC mp_obj_t pyb_timer_callback(mp_obj_t self_in, mp_obj_t callback);

113
114
115
116
117
118
119
void timer_init0(void) {
    tim3_counter = 0;
    for (uint i = 0; i < PYB_TIMER_OBJ_ALL_NUM; i++) {
        pyb_timer_obj_all[i] = NULL;
    }
}

120
121
122
123
124
125
126
127
128
129
// unregister all interrupt sources
void timer_deinit(void) {
    for (uint i = 0; i < PYB_TIMER_OBJ_ALL_NUM; i++) {
        pyb_timer_obj_t *tim = pyb_timer_obj_all[i];
        if (tim != NULL) {
            pyb_timer_deinit(tim);
        }
    }
}

130
131
132
133
134
135
// TIM3 is set-up for the USB CDC interface
void timer_tim3_init(void) {
    // set up the timer for USBD CDC
    __TIM3_CLK_ENABLE();

    TIM3_Handle.Instance = TIM3;
136
137
    TIM3_Handle.Init.Period = (USBD_CDC_POLLING_INTERVAL*1000) - 1; // TIM3 fires every USBD_CDC_POLLING_INTERVAL ms
    TIM3_Handle.Init.Prescaler = 84-1; // for System clock at 168MHz, TIM3 runs at 1MHz
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
    TIM3_Handle.Init.ClockDivision = 0;
    TIM3_Handle.Init.CounterMode = TIM_COUNTERMODE_UP;
    HAL_TIM_Base_Init(&TIM3_Handle);

    HAL_NVIC_SetPriority(TIM3_IRQn, 6, 0);
    HAL_NVIC_EnableIRQ(TIM3_IRQn);

    if (HAL_TIM_Base_Start(&TIM3_Handle) != HAL_OK) {
        /* Starting Error */
    }
}

/* unused
void timer_tim3_deinit(void) {
    // reset TIM3 timer
    __TIM3_FORCE_RESET();
    __TIM3_RELEASE_RESET();
}
*/

// TIM5 is set-up for the servo controller
159
// This function inits but does not start the timer
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
void timer_tim5_init(void) {
    // TIM5 clock enable
    __TIM5_CLK_ENABLE();

    // set up and enable interrupt
    HAL_NVIC_SetPriority(TIM5_IRQn, 6, 0);
    HAL_NVIC_EnableIRQ(TIM5_IRQn);

    // PWM clock configuration
    TIM5_Handle.Instance = TIM5;
    TIM5_Handle.Init.Period = 2000; // timer cycles at 50Hz
    TIM5_Handle.Init.Prescaler = ((SystemCoreClock / 2) / 100000) - 1; // timer runs at 100kHz
    TIM5_Handle.Init.ClockDivision = 0;
    TIM5_Handle.Init.CounterMode = TIM_COUNTERMODE_UP;
    HAL_TIM_PWM_Init(&TIM5_Handle);
}

177
178
179
180
181
182
183
184
185
// Init TIM6 with a counter-overflow at the given frequency (given in Hz)
// TIM6 is used by the DAC and ADC for auto sampling at a given frequency
// This function inits but does not start the timer
void timer_tim6_init(uint freq) {
    // TIM6 clock enable
    __TIM6_CLK_ENABLE();

    // Timer runs at SystemCoreClock / 2
    // Compute the prescaler value so TIM6 triggers at freq-Hz
186
    uint32_t period = MAX(1, (SystemCoreClock / 2) / freq);
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
    uint32_t prescaler = 1;
    while (period > 0xffff) {
        period >>= 1;
        prescaler <<= 1;
    }

    // Time base clock configuration
    TIM6_Handle.Instance = TIM6;
    TIM6_Handle.Init.Period = period - 1;
    TIM6_Handle.Init.Prescaler = prescaler - 1;
    TIM6_Handle.Init.ClockDivision = 0; // unused for TIM6
    TIM6_Handle.Init.CounterMode = TIM_COUNTERMODE_UP; // unused for TIM6
    HAL_TIM_Base_Init(&TIM6_Handle);
}

202
203
204
205
// Interrupt dispatch
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim) {
    if (htim == &TIM3_Handle) {
        USBD_CDC_HAL_TIM_PeriodElapsedCallback();
206
207
208
209
210
211
212

        // Periodically raise a flash IRQ for the flash storage controller
        if (tim3_counter++ >= 500 / USBD_CDC_POLLING_INTERVAL) {
            tim3_counter = 0;
            NVIC->STIR = FLASH_IRQn;
        }

213
214
215
216
217
    } else if (htim == &TIM5_Handle) {
        servo_timer_irq_callback();
    }
}

218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
/******************************************************************************/
/* Micro Python bindings                                                      */

STATIC void pyb_timer_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
    pyb_timer_obj_t *self = self_in;

    if (self->tim.State == HAL_TIM_STATE_RESET) {
        print(env, "Timer(%u)", self->tim_id);
    } else {
        print(env, "Timer(%u, prescaler=%u, period=%u, mode=%u, div=%u)",
            self->tim_id,
            self->tim.Init.Prescaler,
            self->tim.Init.Period,
            self->tim.Init.CounterMode,
            self->tim.Init.ClockDivision
        );
    }
}
236

237
238
239
240
241
242
/// \method init(*, freq, prescaler, period)
/// Initialise the timer.  Initialisation must be either by frequency (in Hz)
/// or by prescaler and period:
///
///     tim.init(freq=100)                  # set the timer to trigger at 100Hz
///     tim.init(prescaler=100, period=300) # set the prescaler and period directly
243
244
245
246
247
248
STATIC const mp_arg_t pyb_timer_init_args[] = {
    { MP_QSTR_freq,      MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0xffffffff} },
    { MP_QSTR_prescaler, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0xffffffff} },
    { MP_QSTR_period,    MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0xffffffff} },
    { MP_QSTR_mode,      MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = TIM_COUNTERMODE_UP} },
    { MP_QSTR_div,       MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = TIM_CLOCKDIVISION_DIV1} },
249
};
250
#define PYB_TIMER_INIT_NUM_ARGS MP_ARRAY_SIZE(pyb_timer_init_args)
251

252
253
STATIC mp_obj_t pyb_timer_init_helper(pyb_timer_obj_t *self, uint n_args, const mp_obj_t *args, mp_map_t *kw_args) {
    // parse args
254
255
    mp_arg_val_t vals[PYB_TIMER_INIT_NUM_ARGS];
    mp_arg_parse_all(n_args, args, kw_args, PYB_TIMER_INIT_NUM_ARGS, pyb_timer_init_args, vals);
256

257
258
    // set the TIM configuration values
    TIM_Base_InitTypeDef *init = &self->tim.Init;
259

260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
    if (vals[0].u_int != 0xffffffff) {
        // set prescaler and period from frequency

        if (vals[0].u_int == 0) {
            nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "can't have 0 frequency"));
        }

        // work out TIM's clock source
        uint tim_clock;
        if (self->tim_id == 1 || (8 <= self->tim_id && self->tim_id <= 11)) {
            // TIM{1,8,9,10,11} are on APB2
            tim_clock = HAL_RCC_GetPCLK2Freq();
        } else {
            // TIM{2,3,4,5,6,7,12,13,14} are on APB1
            tim_clock = HAL_RCC_GetPCLK1Freq();
        }

        // compute the prescaler value so TIM triggers at freq-Hz
        // dpgeorge: I don't understand why we need to multiply tim_clock by 2
        uint32_t period = MAX(1, 2 * tim_clock / vals[0].u_int);
        uint32_t prescaler = 1;
        while (period > 0xffff) {
            period >>= 1;
            prescaler <<= 1;
        }
        init->Prescaler = prescaler - 1;
        init->Period = period - 1;
    } else if (vals[1].u_int != 0xffffffff && vals[2].u_int != 0xffffffff) {
        // set prescaler and period directly
        init->Prescaler = vals[1].u_int;
        init->Period = vals[2].u_int;
    } else {
        nlr_raise(mp_obj_new_exception_msg(&mp_type_TypeError, "must specify either freq, or prescaler and period"));
    }

    init->CounterMode = vals[3].u_int;
    init->ClockDivision = vals[4].u_int;
    init->RepetitionCounter = 0;

    // init the TIM peripheral
    switch (self->tim_id) {
        case 1: __TIM1_CLK_ENABLE(); break;
        case 2: __TIM2_CLK_ENABLE(); break;
        case 3: __TIM3_CLK_ENABLE(); break;
        case 4: __TIM4_CLK_ENABLE(); break;
        case 5: __TIM5_CLK_ENABLE(); break;
        case 6: __TIM6_CLK_ENABLE(); break;
        case 7: __TIM7_CLK_ENABLE(); break;
        case 8: __TIM8_CLK_ENABLE(); break;
        case 9: __TIM9_CLK_ENABLE(); break;
        case 10: __TIM10_CLK_ENABLE(); break;
        case 11: __TIM11_CLK_ENABLE(); break;
        case 12: __TIM12_CLK_ENABLE(); break;
        case 13: __TIM13_CLK_ENABLE(); break;
        case 14: __TIM14_CLK_ENABLE(); break;
    }
    HAL_TIM_Base_Init(&self->tim);
    HAL_TIM_Base_Start(&self->tim);

    // set the priority (if not a special timer)
    if (self->tim_id != 3 && self->tim_id != 5) {
        HAL_NVIC_SetPriority(self->irqn, 0xe, 0xe); // next-to lowest priority
    }
323
324
325
326

    return mp_const_none;
}

327
328
329
330
/// \classmethod \constructor(id, ...)
/// Construct a new timer object of the given id.  If additional
/// arguments are given, then the timer is initialised by `init(...)`.
/// `id` can be 1 to 14, excluding 3.
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
STATIC mp_obj_t pyb_timer_make_new(mp_obj_t type_in, uint n_args, uint n_kw, const mp_obj_t *args) {
    // check arguments
    mp_arg_check_num(n_args, n_kw, 1, MP_OBJ_FUN_ARGS_MAX, true);

    // create new Timer object
    pyb_timer_obj_t *tim = m_new_obj(pyb_timer_obj_t);
    tim->base.type = &pyb_timer_type;
    tim->callback = mp_const_none;
    memset(&tim->tim, 0, sizeof(tim->tim));

    // get TIM number
    tim->tim_id = mp_obj_get_int(args[0]);

    switch (tim->tim_id) {
        case 1: tim->tim.Instance = TIM1; tim->irqn = TIM1_UP_TIM10_IRQn; break;
        case 2: tim->tim.Instance = TIM2; tim->irqn = TIM2_IRQn; break;
        case 3: nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "Timer 3 is for internal use only")); // TIM3 used for low-level stuff; go via regs if necessary
        case 4: tim->tim.Instance = TIM4; tim->irqn = TIM4_IRQn; break;
        case 5: tim->tim.Instance = TIM5; tim->irqn = TIM5_IRQn; break;
        case 6: tim->tim.Instance = TIM6; tim->irqn = TIM6_DAC_IRQn; break;
        case 7: tim->tim.Instance = TIM7; tim->irqn = TIM7_IRQn; break;
        case 8: tim->tim.Instance = TIM8; tim->irqn = TIM8_UP_TIM13_IRQn; break;
        case 9: tim->tim.Instance = TIM9; tim->irqn = TIM1_BRK_TIM9_IRQn; break;
        case 10: tim->tim.Instance = TIM10; tim->irqn = TIM1_UP_TIM10_IRQn; break;
        case 11: tim->tim.Instance = TIM11; tim->irqn = TIM1_TRG_COM_TIM11_IRQn; break;
        case 12: tim->tim.Instance = TIM12; tim->irqn = TIM8_BRK_TIM12_IRQn; break;
        case 13: tim->tim.Instance = TIM13; tim->irqn = TIM8_UP_TIM13_IRQn; break;
        case 14: tim->tim.Instance = TIM14; tim->irqn = TIM8_TRG_COM_TIM14_IRQn; break;
        default: nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "Timer %d does not exist", tim->tim_id));
    }

    if (n_args > 1 || n_kw > 0) {
        // start the peripheral
        mp_map_t kw_args;
        mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
        pyb_timer_init_helper(tim, n_args - 1, args + 1, &kw_args);
    }

    // set the global variable for interrupt callbacks
    if (tim->tim_id - 1 < PYB_TIMER_OBJ_ALL_NUM) {
        pyb_timer_obj_all[tim->tim_id - 1] = tim;
    }

    return (mp_obj_t)tim;
375
376
}

377
378
STATIC mp_obj_t pyb_timer_init(uint n_args, const mp_obj_t *args, mp_map_t *kw_args) {
    return pyb_timer_init_helper(args[0], n_args - 1, args + 1, kw_args);
379
}
380
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_timer_init_obj, 1, pyb_timer_init);
381

382
383
384
/// \method deinit()
/// Deinitialises the timer.
///
385
386
/// Disables the callback (and the associated irq).
/// Stops the timer, and disables the timer peripheral.
387
STATIC mp_obj_t pyb_timer_deinit(mp_obj_t self_in) {
388
389
390
391
392
393
    pyb_timer_obj_t *self = self_in;

    // Disable the interrupt
    pyb_timer_callback(self_in, mp_const_none);

    HAL_TIM_Base_DeInit(&self->tim);
394
395
396
397
    return mp_const_none;
}
STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_timer_deinit_obj, pyb_timer_deinit);

398
399
/// \method counter([value])
/// Get or set the timer counter.
400
401
402
403
404
405
406
407
408
409
410
411
412
mp_obj_t pyb_timer_counter(uint n_args, const mp_obj_t *args) {
    pyb_timer_obj_t *self = args[0];
    if (n_args == 1) {
        // get
        return mp_obj_new_int(self->tim.Instance->CNT);
    } else {
        // set
        __HAL_TIM_SetCounter(&self->tim, mp_obj_get_int(args[1]));
        return mp_const_none;
    }
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_timer_counter_obj, 1, 2, pyb_timer_counter);

413
414
/// \method prescaler([value])
/// Get or set the prescaler for the timer.
415
416
417
418
419
420
421
422
423
424
425
426
427
mp_obj_t pyb_timer_prescaler(uint n_args, const mp_obj_t *args) {
    pyb_timer_obj_t *self = args[0];
    if (n_args == 1) {
        // get
        return mp_obj_new_int(self->tim.Instance->PSC & 0xffff);
    } else {
        // set
        self->tim.Init.Prescaler = self->tim.Instance->PSC = mp_obj_get_int(args[1]) & 0xffff;
        return mp_const_none;
    }
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_timer_prescaler_obj, 1, 2, pyb_timer_prescaler);

428
429
/// \method period([value])
/// Get or set the period of the timer.
430
431
432
433
434
435
436
437
438
439
440
441
mp_obj_t pyb_timer_period(uint n_args, const mp_obj_t *args) {
    pyb_timer_obj_t *self = args[0];
    if (n_args == 1) {
        // get
        return mp_obj_new_int(self->tim.Instance->ARR & 0xffff);
    } else {
        // set
        __HAL_TIM_SetAutoreload(&self->tim, mp_obj_get_int(args[1]) & 0xffff);
        return mp_const_none;
    }
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_timer_period_obj, 1, 2, pyb_timer_period);
442

443
444
445
446
/// \method callback(fun)
/// Set the function to be called when the timer triggers.
/// `fun` is passed 1 argument, the timer object.
/// If `fun` is `None` then the callback will be disabled.
447
448
449
450
451
452
453
454
455
456
457
458
459
STATIC mp_obj_t pyb_timer_callback(mp_obj_t self_in, mp_obj_t callback) {
    pyb_timer_obj_t *self = self_in;
    if (callback == mp_const_none) {
        // stop interrupt (but not timer)
        __HAL_TIM_DISABLE_IT(&self->tim, TIM_IT_UPDATE);
        self->callback = mp_const_none;
    } else if (mp_obj_is_callable(callback)) {
        self->callback = callback;
        HAL_NVIC_EnableIRQ(self->irqn);
        // start timer, so that it interrupts on overflow
        HAL_TIM_Base_Start_IT(&self->tim);
    } else {
        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "callback must be None or a callable object"));
460
    }
461
    return mp_const_none;
462
}
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
STATIC MP_DEFINE_CONST_FUN_OBJ_2(pyb_timer_callback_obj, pyb_timer_callback);

STATIC const mp_map_elem_t pyb_timer_locals_dict_table[] = {
    // instance methods
    { MP_OBJ_NEW_QSTR(MP_QSTR_init), (mp_obj_t)&pyb_timer_init_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_deinit), (mp_obj_t)&pyb_timer_deinit_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_counter), (mp_obj_t)&pyb_timer_counter_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_prescaler), (mp_obj_t)&pyb_timer_prescaler_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_period), (mp_obj_t)&pyb_timer_period_obj },
    { MP_OBJ_NEW_QSTR(MP_QSTR_callback), (mp_obj_t)&pyb_timer_callback_obj },
};

STATIC MP_DEFINE_CONST_DICT(pyb_timer_locals_dict, pyb_timer_locals_dict_table);

const mp_obj_type_t pyb_timer_type = {
    { &mp_type_type },
    .name = MP_QSTR_Timer,
    .print = pyb_timer_print,
    .make_new = pyb_timer_make_new,
    .locals_dict = (mp_obj_t)&pyb_timer_locals_dict,
};

void timer_irq_handler(uint tim_id) {
    if (tim_id - 1 < PYB_TIMER_OBJ_ALL_NUM) {
        // get the timer object
        pyb_timer_obj_t *tim = pyb_timer_obj_all[tim_id - 1];

        if (tim == NULL) {
            // timer object has not been set, so we can't do anything
            return;
        }
494

495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
        // see if it was a TIM update event (the only event we currently interrupt on)
        if (__HAL_TIM_GET_FLAG(&tim->tim, TIM_FLAG_UPDATE) != RESET) {
            if (__HAL_TIM_GET_ITSTATUS(&tim->tim, TIM_IT_UPDATE) != RESET) {
                // clear the interrupt
                __HAL_TIM_CLEAR_IT(&tim->tim, TIM_IT_UPDATE);

                // execute callback if it's set
                if (tim->callback != mp_const_none) {
                    // When executing code within a handler we must lock the GC to prevent
                    // any memory allocations.  We must also catch any exceptions.
                    gc_lock();
                    nlr_buf_t nlr;
                    if (nlr_push(&nlr) == 0) {
                        mp_call_function_1(tim->callback, tim);
                        nlr_pop();
                    } else {
                        // Uncaught exception; disable the callback so it doesn't run again.
                        tim->callback = mp_const_none;
                        __HAL_TIM_DISABLE_IT(&tim->tim, TIM_IT_UPDATE);
514
                        printf("Uncaught exception in Timer(" UINT_FMT ") interrupt handler\n", tim->tim_id);
515
516
517
518
519
520
                        mp_obj_print_exception((mp_obj_t)nlr.ret_val);
                    }
                    gc_unlock();
                }
            }
        }
521
522
    }
}