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/*
* 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
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