Detailed Description

This file defines the UartOW (UART to Dallas 1-wire) interface for libmraa

    mraa::UartOW uart(0);
    // Reset the ow bus and see if anything is present
    if ((status = uart.reset()) == mraa::SUCCESS) {
        std::cout << "Reset succeeded, device(s) detected!" << std::endl;
    } else {
        std::cout << "Reset failed, returned " << int(status) << ". No devices on bus?" << std::endl;
        return EXIT_FAILURE;
    }
    std::cout << "Looking for devices..." << std::endl;
    // start the search from scratch
    id = uart.search(true);
    if (id.empty()) {
        std::cout << "No devices detected." << std::endl;
        return EXIT_FAILURE;
    }
    while (!id.empty()) {
        // hack so we don't need to cast each element of the romcode
        // for printf purposes
        ptr = (uint8_t*) id.data();
        // The first byte (0) is the device type (family) code.
        // The last byte (7) is the rom code CRC value.  The
        // intervening bytes are the unique 48 bit device ID.
        std::cout << "Device %02d Type 0x%02x ID %02x%02x%02x%02x%02x%02x CRC 0x%02x" << count << ptr[0]
                  << ptr[6] << ptr[5] << ptr[4] << ptr[3] << ptr[2] << ptr[1] << ptr[7] << std::endl;
        count++;
        // continue the search with start argument set to false
        id = uart.search(false);
    }
    std::cout << "Exiting..." << std::endl;

Public Member Functions
	UartOW (int uart)

	UartOW (std::string path)

	UartOW (void *uart_ow_context)

	~UartOW ()

std::string	getDevicePath ()

uint8_t	readByte ()

uint8_t	writeByte (uint8_t byte)

bool	writeBit (bool bit)

mraa::Result	reset ()

mraa::Result	search (bool start, uint8_t *id)

std::string	search (bool start)

mraa::Result	command (uint8_t command, uint8_t *id)

mraa::Result	command (uint8_t command, std::string id)

uint8_t	crc8 (uint8_t *buffer, uint16_t length)

uint8_t	crc8 (std::string buffer)

Constructor & Destructor Documentation

UartOW ( int uart )

inline

UartOW Constructor, takes a pin number which will map directly to the linux uart number, this 'enables' the uart, nothing more

Parameters

uart	the index of the uart to use

Exceptions

std::invalid_argument in case of error

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UartOW ( std::string path )

inline

UartOW Constructor, takes a string to the path of the serial interface that is needed.

Parameters

path	the file path for the UART to use

Exceptions

std::invalid_argument in case of error

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UartOW ( void * uart_ow_context )

inline

UartOW Constructor, takes a pointer to the UartOW context and initialises the UartOW class

Parameters

uart_ow_context void * to a UartOW context

~UartOW ( )

inline

Uart destructor

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Member Function Documentation

std::string getDevicePath ( )

inline

Get string with tty device path within Linux For example. Could point to "/dev/ttyS0"

Returns: char pointer of device path

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uint8_t readByte ( )

inline

Read a byte from the 1-wire bus

Exceptions

std::invalid_argument in case of error

Returns: the byte read

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uint8_t writeByte ( uint8_t byte )

inline

Write a byte to a 1-wire bus

Parameters

byte	the byte to write to the bus

Exceptions

std::invalid_argument in case of error

Returns: the byte read back during the time slot

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bool writeBit ( bool bit )

inline

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.

Parameters

bit	the bit to write to the bus

Exceptions

std::invalid_argument in case of error

Returns: the bit read back during the time slot

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mraa::Result reset ( )

inline

Send a reset pulse to the 1-wire bus and test for device presence

Returns: one of the mraa::Result values

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mraa::Result search	(	bool	start,
		uint8_t *	id
	)

inline

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.

Parameters

start	true to start a search from scratch, false to continue a previously started search
id	the 8-byte rom code id of the current matched device when a device is found

Returns: one of the mraa::Result values

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std::string search ( bool start )

inline

Begin a rom code search of the 1-wire bus. This function implements the 1-wire search algorithm. See the UartOW.cpp example for an idea on how to use this function to identify all devices present on the bus.

Parameters

start true to start a search from scratch, false to continue a previously started search

Returns: an empty string if no [more] devices are found, or a string containing the 8-byte romcode of a detected device.

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mraa::Result command	(	uint8_t	command,
		uint8_t *	id
	)

inline

Send a command byte to a device on the 1-wire bus

Parameters

command	the command byte to send
id	the rom code id of the device to receive the command, NULL for all devices on the bus

Returns: one of the mraa::Result values

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mraa::Result command	(	uint8_t	command,
		std::string	id
	)

inline

Send a command byte to a device on the 1-wire bus, supplying the id as a std::string

Parameters

command	the command byte to send
id	std::string representing the code id of the device to receive the command, or an empty string for all devices on the bus. This string should be 8 bytes in size.