71 lines
3 KiB
C
71 lines
3 KiB
C
// This file is part of the CircuitPython project: https://circuitpython.org
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//
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// SPDX-FileCopyrightText: Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
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//
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// SPDX-License-Identifier: MIT
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#include "common-hal/microcontroller/Pin.h"
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#include "shared-bindings/onewireio/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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// Durations are taken from here: https://www.maximintegrated.com/en/app-notes/index.mvp/id/126
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void common_hal_onewireio_onewire_construct(onewireio_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 common_hal_onewireio_onewire_deinited(onewireio_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 common_hal_onewireio_onewire_deinit(onewireio_onewire_obj_t *self) {
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if (common_hal_onewireio_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 common_hal_onewireio_onewire_reset(onewireio_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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// test if bus returned high (idle) and not stuck at low
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bool idle = common_hal_digitalio_digitalinout_get_value(&self->pin);
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common_hal_mcu_enable_interrupts();
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return value || !idle;
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}
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bool common_hal_onewireio_onewire_read_bit(onewireio_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 common_hal_onewireio_onewire_write_bit(onewireio_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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