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244 lines
8.6 KiB
244 lines
8.6 KiB
#ifndef __ONEWIRE_H__
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#define __ONEWIRE_H__
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#include "FreeRTOS.h"
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#include <stdint.h>
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#include <stdbool.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** @file onewire.h
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*
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* Routines to access devices using the Dallas Semiconductor 1-Wire(tm)
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* protocol.
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*/
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/** Select the table-lookup method of computing the 8-bit CRC
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* by setting this to 1 during compilation. The lookup table enlarges code
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* size by about 250 bytes. By default, a slower but very compact algorithm
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* is used.
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*/
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#ifndef ONEWIRE_CRC8_TABLE
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#define ONEWIRE_CRC8_TABLE 0
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#endif
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/** Type used to hold all 1-Wire device ROM addresses (64-bit) */
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typedef uint64_t onewire_addr_t;
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/** Structure to contain the current state for onewire_search_next(), etc */
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typedef struct {
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uint8_t rom_no[8];
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uint8_t last_discrepancy;
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bool last_device_found;
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} onewire_search_t;
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/** ::ONEWIRE_NONE is an invalid ROM address that will never occur in a device
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* (CRC mismatch), and so can be useful as an indicator for "no-such-device",
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* etc.
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*/
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#define ONEWIRE_NONE ((onewire_addr_t)(0xffffffffffffffffLL))
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/** Perform a 1-Wire reset cycle.
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*
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* @param pin The GPIO pin connected to the 1-Wire bus.
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*
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* @returns `true` if at least one device responds with a presence pulse,
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* `false` if no devices were detected (or the bus is shorted, etc)
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*/
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bool onewire_reset(int pin);
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/** Issue a 1-Wire rom select command to select a particular device.
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*
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* It is necessary to call onewire_reset() before calling this function.
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*
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* @param pin The GPIO pin connected to the 1-Wire bus.
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* @param addr The ROM address of the device to select
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*
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* @returns `true` if the "ROM select" command could be succesfully issued,
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* `false` if there was an error.
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*/
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bool onewire_select(int pin, const onewire_addr_t addr);
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/** Issue a 1-Wire "skip ROM" command to select *all* devices on the bus.
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*
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* It is necessary to call onewire_reset() before calling this function.
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*
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* @param pin The GPIO pin connected to the 1-Wire bus.
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*
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* @returns `true` if the "skip ROM" command could be succesfully issued,
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* `false` if there was an error.
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*/
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bool onewire_skip_rom(int pin);
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/** Write a byte on the onewire bus.
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*
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* The writing code uses open-drain mode and expects the pullup resistor to
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* pull the line high when not driven low. If you need strong power after the
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* write (e.g. DS18B20 in parasite power mode) then call onewire_power() after
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* this is complete to actively drive the line high.
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*
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* @param pin The GPIO pin connected to the 1-Wire bus.
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* @param v The byte value to write
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*
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* @returns `true` if successful, `false` on error.
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*/
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bool onewire_write(int pin, uint8_t v);
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/** Write multiple bytes on the 1-Wire bus.
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*
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* See onewire_write() for more info.
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*
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* @param pin The GPIO pin connected to the 1-Wire bus.
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* @param buf A pointer to the buffer of bytes to be written
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* @param count Number of bytes to write
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*
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* @returns `true` if all bytes written successfully, `false` on error.
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*/
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bool onewire_write_bytes(int pin, const uint8_t *buf, size_t count);
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/** Read a byte from a 1-Wire device.
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*
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* @param pin The GPIO pin connected to the 1-Wire bus.
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*
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* @returns the read byte on success, negative value on error.
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*/
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int onewire_read(int pin);
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/** Read multiple bytes from a 1-Wire device.
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*
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* @param pin The GPIO pin connected to the 1-Wire bus.
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* @param buf A pointer to the buffer to contain the read bytes
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* @param count Number of bytes to read
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*
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* @returns `true` on success, `false` on error.
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*/
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bool onewire_read_bytes(int pin, uint8_t *buf, size_t count);
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/** Actively drive the bus high to provide extra power for certain operations
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* of parasitically-powered devices.
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*
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* For parasitically-powered devices which need more power than can be
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* provided via the normal pull-up resistor, it may be necessary for some
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* operations to drive the bus actively high. This function can be used to
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* perform that operation.
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*
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* The bus can be depowered once it is no longer needed by calling
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* onewire_depower(), or it will be depowered automatically the next time
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* onewire_reset() is called to start another command.
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*
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* Note: Make sure the device(s) you are powering will not pull more current
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* than the ESP8266 is able to supply via its GPIO pins (this is especially
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* important when multiple devices are on the same bus and they are all
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* performing a power-intensive operation at the same time (i.e. multiple
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* DS18B20 sensors, which have all been given a "convert T" operation by using
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* onewire_skip_rom())).
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*
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* Note: This routine will check to make sure that the bus is already high
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* before driving it, to make sure it doesn't attempt to drive it high while
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* something else is pulling it low (which could cause a reset or damage the
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* ESP8266).
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*
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* @param pin The GPIO pin connected to the 1-Wire bus.
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*
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* @returns `true` on success, `false` on error.
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*/
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bool onewire_power(int pin);
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/** Stop forcing power onto the bus.
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*
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* You only need to do this if you previously called onewire_power() to drive
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* the bus high and now want to allow it to float instead. Note that
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* onewire_reset() will also automatically depower the bus first, so you do
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* not need to call this first if you just want to start a new operation.
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*
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* @param pin The GPIO pin connected to the 1-Wire bus.
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*/
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void onewire_depower(int pin);
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/** Clear the search state so that it will start from the beginning on the next
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* call to onewire_search_next().
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*
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* @param search The onewire_search_t structure to reset.
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*/
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void onewire_search_start(onewire_search_t *search);
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/** Setup the search to search for devices with the specified "family code".
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*
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* @param search The onewire_search_t structure to update.
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* @param family_code The "family code" to search for.
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*/
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void onewire_search_prefix(onewire_search_t *search, uint8_t family_code);
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/** Search for the next device on the bus.
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*
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* The order of returned device addresses is deterministic. You will always
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* get the same devices in the same order.
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*
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* @returns the address of the next device on the bus, or ::ONEWIRE_NONE if
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* there is no next address. ::ONEWIRE_NONE might also mean that the bus is
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* shorted, there are no devices, or you have already retrieved all of them.
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*
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* It might be a good idea to check the CRC to make sure you didn't get
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* garbage.
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*/
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onewire_addr_t onewire_search_next(onewire_search_t *search, int pin);
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/** Compute a Dallas Semiconductor 8 bit CRC.
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*
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* These are used in the ROM address and scratchpad registers to verify the
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* transmitted data is correct.
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*/
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uint8_t onewire_crc8(const uint8_t *data, uint8_t len);
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/** Compute the 1-Wire CRC16 and compare it against the received CRC.
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*
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* Example usage (reading a DS2408):
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* @code
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* // Put everything in a buffer so we can compute the CRC easily.
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* uint8_t buf[13];
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* buf[0] = 0xF0; // Read PIO Registers
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* buf[1] = 0x88; // LSB address
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* buf[2] = 0x00; // MSB address
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* onewire_write_bytes(pin, buf, 3); // Write 3 cmd bytes
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* onewire_read_bytes(pin, buf+3, 10); // Read 6 data bytes, 2 0xFF, 2 CRC16
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* if (!onewire_check_crc16(buf, 11, &buf[11])) {
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* // TODO: Handle error.
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* }
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* @endcode
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*
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* @param input Array of bytes to checksum.
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* @param len Number of bytes in `input`
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* @param inverted_crc The two CRC16 bytes in the received data.
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* This should just point into the received data,
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* *not* at a 16-bit integer.
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* @param crc_iv The crc starting value (optional)
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*
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* @returns `true` if the CRC matches, `false` otherwise.
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*/
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bool onewire_check_crc16(const uint8_t* input, size_t len, const uint8_t* inverted_crc, uint16_t crc_iv);
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/** Compute a Dallas Semiconductor 16 bit CRC.
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*
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* This is required to check the integrity of data received from many 1-Wire
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* devices. Note that the CRC computed here is *not* what you'll get from the
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* 1-Wire network, for two reasons:
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* 1. The CRC is transmitted bitwise inverted.
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* 2. Depending on the endian-ness of your processor, the binary
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* representation of the two-byte return value may have a different
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* byte order than the two bytes you get from 1-Wire.
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*
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* @param input Array of bytes to checksum.
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* @param len How many bytes are in `input`.
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* @param crc_iv The crc starting value (optional)
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*
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* @returns the CRC16, as defined by Dallas Semiconductor.
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*/
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uint16_t onewire_crc16(const uint8_t* input, size_t len, uint16_t crc_iv);
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#ifdef __cplusplus
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}
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#endif
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#endif /* __ONEWIRE_H__ */
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