CANNY 7.2 Duo. Dallas 1-Wire Driver

General Description

CANNY 7.2 Duo controller can be used as a MASTER in a single-wire data network Dallas 1-Wire®. The controller is only capable of sending requests for data to slave devices.

All CANNY 7.2 Duo input-output channels can be used to connect the controller to 1-Wire bus. At the same time, that channel must be externally pulled-up to 5V with a 3-7k Ohm resistor. Depending on the specific mode(defined through the function diagram), the CANNY 7.2 Duo implementation makes it possible to communicate with a specific device through the 1-Wire bus by using the device address. This enables the controller to work with several SLAVE devices through one channel. It’s also possible to perform a serial connection of the controller to several 1-Wire buses. In operating modes when device handling by address is not available, therefore you will only be able to connect to one SLAVE node per channel.

Dallas 1-Wire driver operates using the controller’s channel resources, but has a higher priority than the discrete input-output driver. This means that for all channels, for which the Dallas 1-Wire driver is activated, all value changes in registers associated with discrete input-output driver will be ignored.

The SLAVE device needs to have permanent, rather than parasitic, power.

Driver registers

Below is a description of the Dallas 1-Wire® driver registers.

Dallas 1-Wire® driver configuration registers.

To activate the Dallas 1-Wire® driver, you need to write the controller channel number connected to Dallas 1-Wire® bus and the type of the using’s Dallas 1-Wire® device, into the appropriate driver registers.

Note: At any given time, the driver can work with only one of the connected Dallas 1-Wire® buses. You can dynamically switch between buses in the function diagram, allowing you to effectively work with several 1-Wire buses.

ATTENTION! To properly switch between 1-Wire buses, do the following. First, deactivate the Dallas 1-Wire driver by writing 0 to the appropriate register. Then set the channel you want to switch to by writing a value into the appropriate register. Finally, activate the Dallas 1-Wire driver by writing the activation constant to the appropriate register.

Manage requests for information from SLAVE devices and control data received by addressing the appropriate registers, described below.

Note: To avoid data loss when working with several Dallas devices, switch between them only after receiving responses from the connected slaves and processing or saving the data.

Example of channel #8 configured to work with a DS18X20 temperature sensor.
Dallas 1-Wire® Setup Registers.
Register Expected values
Dallas 1-Wire® Mode Setup register 1…N = activates the driver and sets the connected device type (defined by a named constant from the constants directory)
0 = disconnects the channel from the 1-Wire driver, returns channel control to the the discrete IO driver
Dallas 1-Wire® IO Channel Select Register 0…8 = sets the channel number used by the controller to work with the Dallas 1-Wire® bus

The following named constants define channel configuration.

Device type constants.
Constant Permitted values
Dallas 1-Wire® device type DS18X20 temperature sensor, DS1990A reader

With the help of Dallas 1-Wire® driver request registers , the user can specify the address of respondent slave node and send a request for data transfer.

1-Wire driver transmit registers.
Register Expected values
Dallas 1-Wire® Request To Send Register ≥ 1 = sends a request for data to the slave
0 = does not send a request for data to the slave
Dallas 1-Wire® Requested Device ID RAW Data Register SN0:FC 0…0xFFFF = register value: the lower part represents a device family identifier (FC), the upper part contains the first byte of the unique device address (SN0).
Dallas 1-Wire® Requested Device ID RAW Data Register SN2:SN1 0…0xFFFF = register value: the lower part contains the 2nd byte of the unique device address (SN1), the upper part contains the 3rd byte of the unique device address (SN2).
Dallas 1-Wire® Requested Device ID RAW Data Register SN4:SN3 0…0xFFFF = register value: the lower part contains the 4th byte of the unique device address (SN3), the upper part contains the 5th byte of the unique device address (SN4).
Dallas 1-Wire® Requested Device ID 0…0xFFFF = register value: the lower part contains the 6th byte of the unique device address (SN5), the upper part contains ROM-code addressee checksum (CRC).

Note: The 64-bit transmission destination ROM-code setup registers are only used to select a device on the Dallas 1-Wire® bus by its unique number (ROM-code), when multiple devices connected to one bus. If you are working with a single device on the bus and do not know its’ ROM-code, write “0” into all “Requested Device ID *” registers.

When you receive data over the 1-Wire bus, the data is placed into the appropriate receive register, and a control bit is set in the Data Set Ready register.

General receive registers.
Register Return values
Dallas 1-Wire® Data Set Ready Register 1 = denotes that data was successfully received from a slave node and is available in Dallas 1-Wire® driver read registers
0 = denotes that there is no new data in the driver receive registers
Dallas 1-Wire® Error Register 1 = during Dallas 1-Wire® data reception an error occurred, received corrupt data
0 = during Dallas 1-Wire® data reception errors no was occurred
DS1990A mode receive registers.
Register Return values
Dallas 1-Wire® Received Raw Data Register SN0:FC 0…0xFFFF = register value: lower part contains family key identifier (FC), upper part contains the first byte of unique key address (SN0).
Dallas 1-Wire® Received Raw Data Register SN2:SN1 0…0xFFFF = register value: lower part contains the second byte of unique key address (SN1), upper part contains the third byte of unique key address (SN2).
Dallas 1-Wire® Received Raw Data Register SN4:SN3 0…0xFFFF = register value: lower part contains the forth byte of unique key address (SN3), upper part contains the fifth byte of unique key address (SN4).
Dallas 1-Wire® Received Raw Data Register CRC:SN 0…0xFFFF = register value: lower part contains the sixth byte of unique key address (SN5), upper part contains key checksum ROM-code (CRC).
DS18X20 mode receive registers.
Register Return values
DS18X20 Received Temperature Data Register: Integer Part 0…125 = defines the modulo of the integer part of the temperature value measured by the sensor
DS18X20 Received Temperature Data Register: Fractional Part ( x 0.0001) 0…9999 = defines the modulo of the decimal part of the temperature value measured by the sensor
DS18X20 Received Temperature Data Register: Sign (0 = above zero; 1 = below zero) 0 = denotes that the temperature measured by the sensor is above zero 1 = denotes that the temperature measured by the sensor is below zero

Note: When receiving in DS18X20 mode the temperature sensor poll rate (period between sending requests through the “Request to send” register) should be no shorter than 750ms.

Examples

Example of a function diagram working with a DS18X20 temperature sensor.

The temperature sensor connected to channel #8 is polled 1 time per second. When the controller receives data from DS18X20, the Dallas 1-Wire® Data Set Ready Register is set to “1” and data from the temperature reading registers is stored in respective named networks with the help of D Flip-Flops, converted to ASCII and sended to CAN-bus.

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