OneWire Library

The OneWire library provides routines for communication via the Dallas OneWire protocol, e.g. with DS18x20 digital thermometer. OneWire is a Master/Slave protocol, and all communication cabling required is a single wire. OneWire enabled devices should have open collector drivers (with single pull-up resistor) on the shared data line.

Slave devices on the OneWire bus can even get their power supply from data line. For detailed schematic see device datasheet.

Some basic characteristics of this protocol are:

single master system,
low cost,
low transfer rates (up to 16 kbps),
fairly long distances (up to 300 meters),
small data transfer packages.

Each OneWire device also has a unique 64-bit registration number (8-bit device type, 48-bit serial number and 8-bit CRC), so multiple slaves can co-exist on the same bus.

Important :

Oscillator frequency Fosc needs to be at least 4MHz in order to use the routines with Dallas digital thermometers.
This library implements time-based activities, so interrupts need to be disabled when using OneWire library.

Ow_Reset

Prototype	sub function Ow_Reset(dim byref port as byte, dim pin as byte) as longword
Description	Issues OneWire reset signal for DS18x20.
Parameters	`port:` OneWire bus port `pin:` OneWire bus pin
Returns	`0` if the device is present `1` if the device is not present
Requires	Devices compliant with the Dallas OneWire protocol.
Example	Ow_Reset(GPIO_PORT_16_23, 2)
Notes	None.

Ow_Read

Prototype	sub function Ow_Read(dim byref port as byte, dim pin as byte) as byte
Description	Reads one byte of data via the OneWire bus.
Parameters	`port:` OneWire bus port `pin:` OneWire bus pin
Returns	Data read from an external device over the OneWire bus.
Requires	Devices compliant with the Dallas OneWire protocol.
Example	Ow_Read(GPIO_PORT_16_23, 2)
Notes	None.

Ow_Write

Prototype	sub procedure Ow_Write(dim byref port as byte, dim pin, data_ as byte)
Description	Writes one byte of data via the OneWire bus.
Parameters	`port:` OneWire bus port `pin:` OneWire bus pin `data_:` data to be written
Returns	Nothing.
Requires	Devices compliant with the Dallas OneWire protocol.
Example	Ow_Write(GPIO_PORT_16_23, 2)
Notes	None.

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