esp8266,esp32: Implement high-res timers using new tick_hz argument.

machine.Timer now takes a new argument in its constructor (or init method):
tick_hz which specified the units for the period argument.  The period of
the timer in seconds is: period/tick_hz.

For backwards compatibility tick_hz defaults to 1000.  If the user wants to
specify the period (numerator) in microseconds then tick_hz can be set to
1000000.  The user can also specify a period of an arbitrary number of
cycles of an arbitrary frequency using these two arguments.

An additional freq argument has been added to allow frequencies to be
specified directly in Hertz.  This supports floating point values when
available.

1 files changed, 34 insertions, 7 deletions

diff --git a/ports/esp32/machine_timer.c b/ports/esp32/machine_timer.c
index eee77e482..7dca9e014 100644
--- a/ports/esp32/machine_timer.c
+++ b/ports/esp32/machine_timer.c
@@ -37,7 +37,9 @@
 #include "mphalport.h"
 
 #define TIMER_INTR_SEL TIMER_INTR_LEVEL
-#define TIMER_DIVIDER  40000
+#define TIMER_DIVIDER  8
+
+// TIMER_BASE_CLK is normally 80MHz. TIMER_DIVIDER ought to divide this exactly
 #define TIMER_SCALE    (TIMER_BASE_CLK / TIMER_DIVIDER)
 
 #define TIMER_FLAGS    0
@@ -48,7 +50,8 @@ typedef struct _machine_timer_obj_t {
     mp_uint_t index;
 
     mp_uint_t repeat;
-    mp_uint_t period;
+    // ESP32 timers are 64-bit
+    uint64_t period;
 
     mp_obj_t callback;
 
@@ -131,10 +134,23 @@ STATIC void machine_timer_enable(machine_timer_obj_t *self) {
 }
 
 STATIC mp_obj_t machine_timer_init_helper(machine_timer_obj_t *self, mp_uint_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_period,       MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0xffffffff} },
         { MP_QSTR_mode,         MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 1} },
         { MP_QSTR_callback,     MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = mp_const_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} },
+#if MICROPY_PY_BUILTINS_FLOAT
+        { MP_QSTR_freq,         MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = mp_const_none} },
+#else
+        { MP_QSTR_freq,         MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0xffffffff} },
+#endif
     };
 
     machine_timer_disable(self);
@@ -142,10 +158,21 @@ STATIC mp_obj_t machine_timer_init_helper(machine_timer_obj_t *self, mp_uint_t n
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    // Timer uses an 80MHz base clock, which is divided by the divider/scalar, we then convert to ms.
-    self->period = (args[0].u_int * TIMER_BASE_CLK) / (1000 * TIMER_DIVIDER);
-    self->repeat = args[1].u_int;
-    self->callback = args[2].u_obj;
+#if MICROPY_PY_BUILTINS_FLOAT
+    if (args[ARG_freq].u_obj != mp_const_none) {
+        self->period = (uint64_t)(TIMER_SCALE / mp_obj_get_float(args[ARG_freq].u_obj));
+    }
+#else
+    if (args[ARG_freq].u_int != 0xffffffff) {
+        self->period = TIMER_SCALE / ((uint64_t)args[ARG_freq].u_int);
+    }
+#endif
+    else {
+        self->period = (((uint64_t)args[ARG_period].u_int) * TIMER_SCALE) / args[ARG_tick_hz].u_int;
+    }
+
+    self->repeat = args[ARG_mode].u_int;
+    self->callback = args[ARG_callback].u_obj;
     self->handle = NULL;
 
     machine_timer_enable(self);