diff --git a/docs/rp2/quickref.rst b/docs/rp2/quickref.rst
index 23071d77215d5..ec31442990ff4 100644
--- a/docs/rp2/quickref.rst
+++ b/docs/rp2/quickref.rst
@@ -135,6 +135,12 @@ Use the :mod:`machine.Timer` class::
tim = Timer(period=5000, mode=Timer.ONE_SHOT, callback=lambda t:print(1))
tim.init(period=2000, mode=Timer.PERIODIC, callback=lambda t:print(2))
+By default, timer callbacks run as soft IRQs so they can allocate but
+are prone to GC jitter and delays. Pass ``hard=True`` to the ``Timer()``
+constructor or ``init()`` method to run the callback in hard-IRQ context
+instead. This reduces delay and jitter, but see :ref:`isr_rules` for the
+restrictions that apply to hard-IRQ handlers.
+
.. _rp2_Pins_and_GPIO:
diff --git a/ports/rp2/machine_timer.c b/ports/rp2/machine_timer.c
index 6f8b04f10eab0..ffb4c7024308a 100644
--- a/ports/rp2/machine_timer.c
+++ b/ports/rp2/machine_timer.c
@@ -27,6 +27,7 @@
#include "py/runtime.h"
#include "py/mperrno.h"
#include "py/mphal.h"
+#include "py/gc.h"
#include "pico/time.h"
#define ALARM_ID_INVALID (-1)
@@ -40,13 +41,36 @@ typedef struct _machine_timer_obj_t {
uint32_t mode;
uint64_t delta_us; // for periodic mode
mp_obj_t callback;
+ bool ishard;
} machine_timer_obj_t;
const mp_obj_type_t machine_timer_type;
static int64_t alarm_callback(alarm_id_t id, void *user_data) {
machine_timer_obj_t *self = user_data;
- mp_sched_schedule(self->callback, MP_OBJ_FROM_PTR(self));
+
+ if (self->ishard) {
+ // When executing code within a handler we must lock the scheduler to
+ // prevent any scheduled callbacks from running, and lock the GC to
+ // prevent any memory allocations.
+ mp_sched_lock();
+ gc_lock();
+ nlr_buf_t nlr;
+ if (nlr_push(&nlr) == 0) {
+ mp_call_function_1(self->callback, MP_OBJ_FROM_PTR(self));
+ nlr_pop();
+ } else {
+ // Uncaught exception; disable the callback so it doesn't run again.
+ self->mode = TIMER_MODE_ONE_SHOT;
+ mp_printf(MICROPY_ERROR_PRINTER, "uncaught exception in timer callback\n");
+ mp_obj_print_exception(MICROPY_ERROR_PRINTER, MP_OBJ_FROM_PTR(nlr.ret_val));
+ }
+ gc_unlock();
+ mp_sched_unlock();
+ } else {
+ mp_sched_schedule(self->callback, MP_OBJ_FROM_PTR(self));
+ }
+
if (self->mode == TIMER_MODE_ONE_SHOT) {
return 0;
} else {
@@ -66,13 +90,14 @@ static void machine_timer_print(const mp_print_t *print, mp_obj_t self_in, mp_pr
}
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, };
+ enum { ARG_mode, ARG_callback, ARG_period, ARG_tick_hz, ARG_freq, ARG_hard, };
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_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
{ 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} },
+ { MP_QSTR_hard, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
};
// Parse args
@@ -96,6 +121,7 @@ static mp_obj_t machine_timer_init_helper(machine_timer_obj_t *self, size_t n_ar
}
self->callback = args[ARG_callback].u_obj;
+ self->ishard = args[ARG_hard].u_bool;
self->alarm_id = alarm_pool_add_alarm_in_us(self->pool, self->delta_us, alarm_callback, self, true);
if (self->alarm_id == -1) {
mp_raise_OSError(MP_ENOMEM);
diff --git a/tests/ports/rp2/rp2_machine_timer.py b/tests/ports/rp2/rp2_machine_timer.py
new file mode 100644
index 0000000000000..ac4efcf7f3835
--- /dev/null
+++ b/tests/ports/rp2/rp2_machine_timer.py
@@ -0,0 +1,20 @@
+from machine import Timer
+from time import sleep_ms
+
+# Test the rp2-specific adjustable tick_hz and hard/soft IRQ handlers
+# for both one-shot and periodic timers.
+
+modes = {Timer.ONE_SHOT: "one-shot", Timer.PERIODIC: "periodic"}
+kinds = {False: "soft", True: "hard"}
+
+for mode in modes:
+ for hard in kinds:
+ for period in 2, 4:
+ timer = Timer(
+ mode=mode,
+ period=period,
+ hard=hard,
+ callback=lambda t: print("callback", modes[mode], kinds[hard], period),
+ )
+ sleep_ms(9)
+ timer.deinit()
diff --git a/tests/ports/rp2/rp2_machine_timer.py.exp b/tests/ports/rp2/rp2_machine_timer.py.exp
new file mode 100644
index 0000000000000..b3dd93dfabfa8
--- /dev/null
+++ b/tests/ports/rp2/rp2_machine_timer.py.exp
@@ -0,0 +1,16 @@
+callback one-shot soft 2
+callback one-shot soft 4
+callback one-shot hard 2
+callback one-shot hard 4
+callback periodic soft 2
+callback periodic soft 2
+callback periodic soft 2
+callback periodic soft 2
+callback periodic soft 4
+callback periodic soft 4
+callback periodic hard 2
+callback periodic hard 2
+callback periodic hard 2
+callback periodic hard 2
+callback periodic hard 4
+callback periodic hard 4
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