d5e9ab6e61
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.
90 lines
2.9 KiB
C
90 lines
2.9 KiB
C
/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2016 Damien P. George
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include <stdio.h>
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#include "py/runtime.h"
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#include "py/mperrno.h"
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#include "py/mphal.h"
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#include "extmod/machine_pulse.h"
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#include "drivers/dht/dht.h"
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STATIC mp_obj_t dht_readinto(mp_obj_t pin_in, mp_obj_t buf_in) {
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mp_hal_pin_obj_t pin = mp_hal_get_pin_obj(pin_in);
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mp_hal_pin_open_drain(pin);
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mp_buffer_info_t bufinfo;
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mp_get_buffer_raise(buf_in, &bufinfo, MP_BUFFER_WRITE);
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if (bufinfo.len < 5) {
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nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "buffer too small"));
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}
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// issue start command
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mp_hal_pin_od_high(pin);
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mp_hal_delay_ms(250);
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mp_hal_pin_od_low(pin);
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mp_hal_delay_ms(18);
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mp_uint_t irq_state = mp_hal_quiet_timing_enter();
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// release the line so the device can respond
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mp_hal_pin_od_high(pin);
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mp_hal_delay_us_fast(10);
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// wait for device to respond
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mp_uint_t ticks = mp_hal_ticks_us();
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while (mp_hal_pin_read(pin) != 0) {
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if ((mp_uint_t)(mp_hal_ticks_us() - ticks) > 100) {
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goto timeout;
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}
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}
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// time pulse, should be 80us
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ticks = machine_time_pulse_us(pin, 1, 150);
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if ((mp_int_t)ticks < 0) {
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goto timeout;
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}
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// time 40 pulses for data (either 26us or 70us)
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uint8_t *buf = bufinfo.buf;
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for (int i = 0; i < 40; ++i) {
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ticks = machine_time_pulse_us(pin, 1, 100);
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if ((mp_int_t)ticks < 0) {
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goto timeout;
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}
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buf[i / 8] = (buf[i / 8] << 1) | (ticks > 48);
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}
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mp_hal_quiet_timing_exit(irq_state);
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return mp_const_none;
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timeout:
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mp_hal_quiet_timing_exit(irq_state);
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mp_raise_OSError(MP_ETIMEDOUT);
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}
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MP_DEFINE_CONST_FUN_OBJ_2(dht_readinto_obj, dht_readinto);
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