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