peripheral/libmraa/api/mraa/uart_ow.h

/*
 * Author: Jon Trulson <jtrulson@ics.com>
 * Copyright (c) 2016 Intel Corporation
 *
 * 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.
 */

#pragma once

/**
 * @file
 * @brief UART OW module
 *
 * This module allows one to use MRAA's UART support in order to
 * interact with Dallas 1-wire compliant devices on a 1-wire bus.  It
 * makes use of the UART for timing purposes.  The principle of
 * operation is described here:
 * https://www.maximintegrated.com/en/app-notes/index.mvp/id/214
 *
 * It is important the you use a UART with CMOS/TTL level voltages
 * (3.3v/5v) RX and TX lines.  DO NOT use standard RS232 level
 * voltages, or you are going to have a bad day.
 *
 * In addition, a diode should be placed across the RX and
 * TX lines like so:
 *
 * -|
 * U|
 * A| TX---|<--+
 * R|          |
 * T| RX-------o--------o 1-wire data bus
 * -|
 *
 * The diode on TX is a 1N4148 (cheap and common), with the cathode
 * connected to TX, and the anode connected to RX and the rest of the
 * 1-wire data line.
 *
 * @snippet uart_ow.c Interesting
 */

#ifdef __cplusplus
extern "C" {
#endif

#include <stdio.h>

#include "common.h"
#include "uart.h"

/* for now, we simply use the normal MRAA UART context */
typedef struct _mraa_uart_ow {
    mraa_uart_context uart;
    /* search state */
    unsigned char ROM_NO[8]; /* 8 byte (64b) rom code */
    int LastDiscrepancy;
    int LastFamilyDiscrepancy;
    mraa_boolean_t LastDeviceFlag;
} *mraa_uart_ow_context;

/* 8 bytes (64 bits) for a device rom code */
static const int MRAA_UART_OW_ROMCODE_SIZE = 8;

/**
 * UART One Wire ROM related Command bytes
 */
typedef enum {
    MRAA_UART_OW_CMD_READ_ROM = 0x33,         /**< read rom, when only one device on bus */
    MRAA_UART_OW_CMD_MATCH_ROM = 0x55,        /**< match a specific rom code */
    MRAA_UART_OW_CMD_SKIP_ROM = 0xcc,         /**< skip match/search rom */
    MRAA_UART_OW_CMD_SEARCH_ROM_ALARM = 0xec, /**< search all roms in alarm state */
    MRAA_UART_OW_CMD_SEARCH_ROM = 0xf0        /**< search all rom codes */
} mraa_uart_ow_rom_cmd_t;

/**
 * Initialise uart_ow_context, uses UART board mapping
 *
 * @param uart the index of the uart set to use
 * @return uart_ow context or NULL
 */
mraa_uart_ow_context mraa_uart_ow_init(int uart);

/**
 * Initialise a raw uart_ow_context. No board setup.
 *
 * @param path for example "/dev/ttyS0"
 * @return uart_ow context or NULL
 */
mraa_uart_ow_context mraa_uart_ow_init_raw(const char* path);

/**
 * Get char pointer with tty device path within Linux
 * For example. Could point to "/dev/ttyS0"
 *
 * @param dev uart_ow context
 * @return char pointer of device path
 */
const char* mraa_uart_ow_get_dev_path(mraa_uart_ow_context dev);

/**
 * Destroy a mraa_uart_ow_context
 *
 * @param dev uart_ow context
 * @return mraa_result_t
 */
mraa_result_t mraa_uart_ow_stop(mraa_uart_ow_context dev);

/**
 * Read a byte from the 1-wire bus
 *
 * @param dev uart_ow context
 * @return the byte read or -1 for error
 */
int mraa_uart_ow_read_byte(mraa_uart_ow_context dev);

/**
 * Write a byte to a 1-wire bus
 *
 * @param dev uart_ow context
 * @param byte the byte to write to the bus
 * @return the byte read back during the time slot or -1 for error
 */
int mraa_uart_ow_write_byte(mraa_uart_ow_context dev, uint8_t byte);

/**
 * Write a bit to a 1-wire bus and read a bit corresponding to the
 * time slot back.  This is possible due to the way we wired the TX
 * and RX together with a diode, forming a loopback.
 *
 * @param dev uart_ow context
 * @param bit the bit to write to the bus
 * @return the bit read back during the time slot or -1 for error
 */
int mraa_uart_ow_bit(mraa_uart_ow_context dev, uint8_t bit);

/**
 * Send a reset pulse to the 1-wire bus and test for device presence
 *
 * @param dev uart_ow context
 * @return one of the mraa_result_t values
 */
mraa_result_t mraa_uart_ow_reset(mraa_uart_ow_context dev);

/**
 * Begin a rom code search of the 1-wire bus.  This function
 * implements the 1-wire search algorithm.  See the uart_ow.c example
 * for an idea on how to use this function to identify all devices
 * present on the bus.
 *
 * @param dev uart_ow context
 * @param start true to start a new search from scratch, false to
 * continue an existing search
 * @param id the 8-byte rom code id of the current matched device when
 * a device is found
 * @return one of the mraa_result_t values
 */
mraa_result_t mraa_uart_ow_rom_search(mraa_uart_ow_context dev, mraa_boolean_t start, uint8_t* id);

/**
 * Send a command byte to a device on the 1-wire bus
 *
 * @param dev uart_ow context
 * @param command the command byte to send
 * @param id the rom code id of the device to receive the command,
 * NULL for all devices on the bus
 * @return one of the mraa_result_t values
 */
mraa_result_t mraa_uart_ow_command(mraa_uart_ow_context dev, uint8_t command, uint8_t* id);

/**
 * Perform a Dallas 1-wire compliant CRC8 computation on a buffer
 *
 * @param buffer the buffer containing the data
 * @param length the length of the buffer
 * @return the computed CRC
 */
uint8_t mraa_uart_ow_crc8(uint8_t* buffer, uint16_t length);

#ifdef __cplusplus
}
#endif