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circuitpython/shared-module/bitbangio/OneWire.c

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3.9 KiB

/*
* This file is part of the Micro Python project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
*
* 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 "common-hal/microcontroller/Pin.h"
#include "shared-bindings/bitbangio/OneWire.h"
#include "shared-bindings/microcontroller/__init__.h"
#include "shared-bindings/digitalio/DigitalInOut.h"
#include "shared-module/bitbangio/types.h"
// Durations are taken from here: https://www.maximintegrated.com/en/app-notes/index.mvp/id/126
void shared_module_bitbangio_onewire_construct(bitbangio_onewire_obj_t* self,
const mcu_pin_obj_t* pin) {
self->pin.base.type = &digitalio_digitalinout_type;
common_hal_digitalio_digitalinout_construct(&self->pin, pin);
}
bool shared_module_bitbangio_onewire_deinited(bitbangio_onewire_obj_t* self) {
return common_hal_digitalio_digitalinout_deinited(&self->pin);
}
void shared_module_bitbangio_onewire_deinit(bitbangio_onewire_obj_t* self) {
if (shared_module_bitbangio_onewire_deinited(self)) {
return;
}
common_hal_digitalio_digitalinout_deinit(&self->pin);
}
// We use common_hal_mcu_delay_us(). It should not be dependent on interrupts
// to do accurate timekeeping, since we disable interrupts during the delays below.
bool shared_module_bitbangio_onewire_reset(bitbangio_onewire_obj_t* self) {
common_hal_mcu_disable_interrupts();
common_hal_digitalio_digitalinout_switch_to_output(&self->pin, false, DRIVE_MODE_OPEN_DRAIN);
common_hal_mcu_delay_us(480);
common_hal_digitalio_digitalinout_switch_to_input(&self->pin, PULL_NONE);
common_hal_mcu_delay_us(70);
bool value = common_hal_digitalio_digitalinout_get_value(&self->pin);
common_hal_mcu_delay_us(410);
common_hal_mcu_enable_interrupts();
return value;
}
bool shared_module_bitbangio_onewire_read_bit(bitbangio_onewire_obj_t* self) {
common_hal_mcu_disable_interrupts();
common_hal_digitalio_digitalinout_switch_to_output(&self->pin, false, DRIVE_MODE_OPEN_DRAIN);
common_hal_mcu_delay_us(6);
common_hal_digitalio_digitalinout_switch_to_input(&self->pin, PULL_NONE);
// TODO(tannewt): Test with more devices and maybe make the delays
// configurable. This should be 9 by the datasheet but all bits read as 1
// then.
common_hal_mcu_delay_us(6);
bool value = common_hal_digitalio_digitalinout_get_value(&self->pin);
common_hal_mcu_delay_us(55);
common_hal_mcu_enable_interrupts();
return value;
}
void shared_module_bitbangio_onewire_write_bit(bitbangio_onewire_obj_t* self,
bool bit) {
common_hal_mcu_disable_interrupts();
common_hal_digitalio_digitalinout_switch_to_output(&self->pin, false, DRIVE_MODE_OPEN_DRAIN);
common_hal_mcu_delay_us(bit? 6 : 60);
common_hal_digitalio_digitalinout_switch_to_input(&self->pin, PULL_NONE);
common_hal_mcu_delay_us(bit? 64 : 10);
common_hal_mcu_enable_interrupts();
}