extmod: Add machine time_pulse_us function (at C and Python level).

The C implementation is taken from the DHT driver.

drivers/dht/dht.c

@@ -29,24 +29,9 @@
 #include "py/runtime.h"
 #include "py/mperrno.h"
 #include "py/mphal.h"
+#include "extmod/machine_pulse.h"
 #include "drivers/dht/dht.h"
 
-STATIC mp_uint_t time_pulse_us(mp_hal_pin_obj_t pin, int pulse_value, mp_uint_t timeout) {
-    mp_uint_t start = mp_hal_ticks_us();
-    while (mp_hal_pin_read(pin) != pulse_value) {
-        if ((mp_uint_t)(mp_hal_ticks_us() - start) >= timeout) {
-            return (mp_uint_t)-1;
-        }
-    }
-    start = mp_hal_ticks_us();
-    while (mp_hal_pin_read(pin) == pulse_value) {
-        if ((mp_uint_t)(mp_hal_ticks_us() - start) >= timeout) {
-            return (mp_uint_t)-1;
-        }
-    }
-    return mp_hal_ticks_us() - start;
-}
-
 STATIC mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
     mp_hal_pin_obj_t pin = mp_hal_get_pin_obj(pin_in);
     mp_hal_pin_open_drain(pin);
@@ -79,7 +64,7 @@ STATIC mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
     }
 
     // time pulse, should be 80us
-    ticks = time_pulse_us(pin, 1, 150);
+    ticks = machine_time_pulse_us(pin, 1, 150);
     if (ticks == (mp_uint_t)-1) {
         goto timeout;
     }
@@ -87,7 +72,7 @@ STATIC mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
     // time 40 pulses for data (either 26us or 70us)
     uint8_t *buf = bufinfo.buf;
     for (int i = 0; i < 40; ++i) {
-        ticks = time_pulse_us(pin, 1, 100);
+        ticks = machine_time_pulse_us(pin, 1, 100);
         if (ticks == (mp_uint_t)-1) {
             goto timeout;
         }

extmod/machine_pulse.c

@@ -0,0 +1,67 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 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.
+ */
+
+#include "py/runtime.h"
+#include "py/mperrno.h"
+#include "extmod/machine_pulse.h"
+
+#if MICROPY_PY_MACHINE
+
+mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t timeout_us) {
+    mp_uint_t start = mp_hal_ticks_us();
+    while (mp_hal_pin_read(pin) != pulse_level) {
+        if ((mp_uint_t)(mp_hal_ticks_us() - start) >= timeout_us) {
+            return (mp_uint_t)-1;
+        }
+    }
+    start = mp_hal_ticks_us();
+    while (mp_hal_pin_read(pin) == pulse_level) {
+        if ((mp_uint_t)(mp_hal_ticks_us() - start) >= timeout_us) {
+            return (mp_uint_t)-1;
+        }
+    }
+    return mp_hal_ticks_us() - start;
+}
+
+STATIC mp_obj_t machine_time_pulse_us_(size_t n_args, const mp_obj_t *args) {
+    mp_hal_pin_obj_t pin = mp_hal_get_pin_obj(args[0]);
+    int level = 0;
+    if (mp_obj_is_true(args[1])) {
+        level = 1;
+    }
+    mp_uint_t timeout_us = 1000000;
+    if (n_args > 2) {
+        timeout_us = mp_obj_get_int(args[2]);
+    }
+    mp_uint_t us = machine_time_pulse_us(pin, level, timeout_us);
+    if (us == (mp_uint_t)-1) {
+        nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(MP_ETIMEDOUT)));
+    }
+    return mp_obj_new_int(us);
+}
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_time_pulse_us_obj, 2, 3, machine_time_pulse_us_);
+
+#endif

extmod/machine_pulse.h

@@ -0,0 +1,37 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 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.
+ */
+
+#ifndef __MICROPY_INCLUDED_EXTMOD_MACHINE_PULSE_H__
+#define __MICROPY_INCLUDED_EXTMOD_MACHINE_PULSE_H__
+
+#include "py/obj.h"
+#include "py/mphal.h"
+
+mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t timeout_us);
+
+MP_DECLARE_CONST_FUN_OBJ(machine_time_pulse_us_obj);
+
+#endif // __MICROPY_INCLUDED_EXTMOD_MACHINE_PULSE_H__

py/py.mk

@@ -176,6 +176,7 @@ PY_O_BASENAME = \
 	../extmod/modubinascii.o \
 	../extmod/virtpin.o \
 	../extmod/machine_mem.o \
+	../extmod/machine_pulse.o \
 	../extmod/machine_i2c.o \
 	../extmod/modussl.o \
 	../extmod/modurandom.o \