From d5e9ab6e61729f533dbed5c2b6b27307ce6c3b55 Mon Sep 17 00:00:00 2001
From: Paul Sokolovsky <pfalcon@users.sourceforge.net>
Date: Sun, 5 Feb 2017 14:20:17 +0300
Subject: [PATCH] extmod/machine_pulse: Make time_pulse_us() not throw
exceptions.
machine.time_pulse_us() is intended to provide very fine timing, including
while working with signal bursts, where each transition is tracked in row.
Throwing and handling an exception may take too much time and "signal loss".
So instead, in case of a timeout, just return negative value. Cases of
timeout while waiting for initial signal stabilization, and during actual
timing, are recognized.
The documentation is updated accordingly, and rewritten somewhat to clarify
the function behavior.
---
docs/library/machine.rst | 11 +++++++----
drivers/dht/dht.c | 4 ++--
extmod/machine_pulse.c | 6 ++----
tests/extmod/machine_pulse.py | 11 ++---------
tests/extmod/machine_pulse.py.exp | 4 ++--
5 files changed, 15 insertions(+), 21 deletions(-)
diff --git a/docs/library/machine.rst b/docs/library/machine.rst
index 753f6b417..c6da71585 100644
--- a/docs/library/machine.rst
+++ b/docs/library/machine.rst
@@ -118,12 +118,15 @@ Miscellaneous functions
microseconds. The `pulse_level` argument should be 0 to time a low pulse
or 1 to time a high pulse.
- The function first waits while the pin input is different to the `pulse_level`
- parameter, then times the duration that the pin is equal to `pulse_level`.
+ If the current input value of the pin is different to `pulse_level`,
+ the function first (*) waits until the pin input becomes equal to `pulse_level`,
+ then (**) times the duration that the pin is equal to `pulse_level`.
If the pin is already equal to `pulse_level` then timing starts straight away.
- The function will raise an OSError with ETIMEDOUT if either of the waits is
- longer than the given timeout value (which is in microseconds).
+ The function will return -2 if there was timeout waiting for condition marked
+ (*) above, and -1 if there was timeout during the main measurement, marked (**)
+ above. The timeout is the same for both cases and given by `timeout_us` (which
+ is in microseconds).
.. _machine_constants:
diff --git a/drivers/dht/dht.c b/drivers/dht/dht.c
index 1f0cffc6f..6bdda44b4 100644
--- a/drivers/dht/dht.c
+++ b/drivers/dht/dht.c
@@ -65,7 +65,7 @@ STATIC mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
// time pulse, should be 80us
ticks = machine_time_pulse_us(pin, 1, 150);
- if (ticks == (mp_uint_t)-1) {
+ if ((mp_int_t)ticks < 0) {
goto timeout;
}
@@ -73,7 +73,7 @@ STATIC mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
uint8_t *buf = bufinfo.buf;
for (int i = 0; i < 40; ++i) {
ticks = machine_time_pulse_us(pin, 1, 100);
- if (ticks == (mp_uint_t)-1) {
+ if ((mp_int_t)ticks < 0) {
goto timeout;
}
buf[i / 8] = (buf[i / 8] << 1) | (ticks > 48);
diff --git a/extmod/machine_pulse.c b/extmod/machine_pulse.c
index b2a78d72e..5f837479d 100644
--- a/extmod/machine_pulse.c
+++ b/extmod/machine_pulse.c
@@ -34,7 +34,7 @@ mp_uint_t machine_time_pulse_us(mp_hal_pin_obj_t pin, int pulse_level, mp_uint_t
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;
+ return (mp_uint_t)-2;
}
}
start = mp_hal_ticks_us();
@@ -57,9 +57,7 @@ STATIC mp_obj_t machine_time_pulse_us_(size_t n_args, const mp_obj_t *args) {
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) {
- mp_raise_OSError(MP_ETIMEDOUT);
- }
+ // May return -1 or -2 in case of timeout
return mp_obj_new_int(us);
}
MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_time_pulse_us_obj, 2, 3, machine_time_pulse_us_);
diff --git a/tests/extmod/machine_pulse.py b/tests/extmod/machine_pulse.py
index b6e126435..6491b5409 100644
--- a/tests/extmod/machine_pulse.py
+++ b/tests/extmod/machine_pulse.py
@@ -43,12 +43,5 @@ t = machine.time_pulse_us(p, 0)
print(type(t))
p = ConstPin(0)
-try:
- machine.time_pulse_us(p, 1, 10)
-except OSError:
- print("OSError")
-
-try:
- machine.time_pulse_us(p, 0, 10)
-except OSError:
- print("OSError")
+print(machine.time_pulse_us(p, 1, 10))
+print(machine.time_pulse_us(p, 0, 10))
diff --git a/tests/extmod/machine_pulse.py.exp b/tests/extmod/machine_pulse.py.exp
index f9a474218..20d4c1043 100644
--- a/tests/extmod/machine_pulse.py.exp
+++ b/tests/extmod/machine_pulse.py.exp
@@ -5,5 +5,5 @@ value: 1
value: 0
value: 1
<class 'int'>
-OSError
-OSError
+-2
+-1
--
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