CANNY 7, Dallas 1-Wire Driver

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General Description[edit]

Controller CANNY 7 can be used as a master node in a single-wire data network Dallas® 1-Wire®, while it has the ability to only send requests for data from slave devices.

Any of CANNY 7 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 resistor 3-7k Ohm. Consistently reassigning driver channels, it's possible to arrange up to 11 independent connections 1-Wire. Wherein device addressing and device handling by address is not available, therefore, in 1-Wire mode it is possible to connect only one SLAVE node at a time to controllers' channel.

Driver Dallas 1-Wire in its operation uses controller channels' resources, but has a higher priority than discrete input-output driver.Thus, upon activation Dallas 1-Wire driver, for channels involved in to its operation, change values in associated registers of discrete input-output driver will be ignored.

The slave must have a permanent, rather than parasitic power.

Dallas 1-Wire® driver[edit]

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

Dallas 1-Wire® driver configuration registers.

To activate Dallas 1-Wire® driver, you need to select the controller channel number connected to Dallas 1-Wire® bus, in the appropriate driver register.

Note: At any given time, the driver can work with only one of the connected Dallas 1-Wire® bus, when it is allowed to dynamically switch between buses in the implementation of the functional diagram.

Sent requests management to get information from the slaves and control receiving of their responses (sensors poll) is performed by appropriate registers of 1-Wire driver.

Note: To avoid data loss, when working with several Dallas buses, perform switching between them only after receiving responses from the slaves requested by the controller and processing or saving the data.

Example of channel #5 configured to work with a temperature sensor DS18X20.

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Dallas 1-Wire® Setup Registers.

Address Expected values
Dallas 1-Wire® Mode Setup register
1...65535 = driver activation and setting the device type (defined by a special constant of the constants directory);
0 = disconnect the channel from 1-Wire driver, return channel control to IO channels driver and allow status changing from the functional diagram.
Dallas 1-Wire® IO Channel Select Register
0...10 = set the channel number used by the controller to work with Dallas 1-Wire® bus .


Channel configuration to operate in this mode is set by the following named constants:

Parameter List of expected values
Dallas 1-Wire® device type DS18X20 temperature sensor, CP-Z reader in the DS1990A emulation mode, DS1990A reader


Dallas 1-Wire® Request Registers.

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.

Address Expected values
Dallas 1-Wire® Request To Send Register
1 = send a request for data to the slave;
0 = do not send a request for data to the slave.
Dallas 1-Wire® Requested Device ID RAW Data Register SN0:FC
0...65535 = register value: the lower part represent 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...65535 = 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...65535 = 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 RAW Data Register CRC:SN5
0...65535 = 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 setup registers of Dallas 1-Wire® 64-bit transmission destination ROM-code is only used to select a device on the Dallas 1-Wire® bus by its unique number (ROM-code), in case of multiple devices connected to the same bus. During operation with a single device on the bus, when its ROM- code unknown, set "0" value into all registers of Dallas transmission destination ROM-code.


Dallas 1-Wire® Receive Registers.

During its operation, upon reception of responses from the slave devices to the controller data requests, according to Dallas 1-Wire® driver configuration, stored in its corresponding receiving registers.

General receive registers.

Address Return values
Dallas 1-Wire® Data Set Ready Register
1 = successfully received data from the slave node and it is available in Dallas 1-Wire® driver read registers;
0 = there is no actual data in the driver receive buffer.


iButton® DS1990A Receive Mode Registers.

Address Return values
Dallas 1-Wire® Received Raw Data Register D0:FC
0...65535 = register value: lower part contains family key identifier (FC), higher part contains the first byte of unique key address (SN0).
Dallas 1-Wire® Received Raw Data Register D2:D1
0...65535 = register value: lower part contains the second byte of unique key address (SN1), higher part contains the third byte of unique key address (SN2).
Dallas 1-Wire® Received Raw Data Register D4:D3
0...65535 = register value: lower part contains the forth byte of unique key address (SN3), higher part contains the fifth byte of unique key address (SN4).
Dallas 1-Wire® Received Raw Data Register CRC:D5
0...65535 = register value: lower part contains the sixth byte of unique key address (SN5), higher part contains key checksum ROM-code (CRC).


DS18X20 Receive Mode Registers.

Address Returning values
DS18X20 Received Temperature Data Register: Integer Part
0...125 = modulo of integer part of temperature value measured by the sensor.
DS18X20 Received Temperature Data Register: Fractional Part ( x 0.0001)
0...9999 = modulo of decimal part of temperature value measured by the sensor.
DS18X20 Received Temperature Data Register: Sign (0 = above zero; 1 = below zero)
0 = the temperature measured by the sensor is above zero;
1 = the temperature measured by the sensor is below zero.
Note: When receiving in DS18X20 mode, temperature sensor duty cycle, those send requests via Dallas transmission start register, should not be less than 750ms.

Example of a functional diagram working with DS18X20 temperature sensor.

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temperature sensor poll, connected to the channel #5, carried out 1 time per second. When receiving data from DS18X20, in Dallas 1-Wire® Data Set Ready Register appears value "1" and data from the temperature reading registers, with help of D flip-flops, is stored in respective named networks for further processing.

Sensor connection circuit.

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See also[edit]

CANNY 7

CANNY 7, I²C Driver