Theoretically, up to 256 devices can be connected to a single 1-Wire bus, but in practice, the maximum number is limited by the bus capacitance and the quality of the wiring. A good rule of thumb is to limit the number of devices to 10-20 per bus.
To ensure accurate temperature readings, make sure to follow proper wiring and layout practices, avoid electromagnetic interference (EMI), and use a high-quality 1-Wire bus. Also, perform a parasite power supply configuration to minimize power consumption and noise.
The VDD pin is used to power the internal logic of the DS18B20+. It is not necessary to connect VDD to an external power source, as the device can be powered parasitically through the 1-Wire bus. However, if an external power source is used, it must be within the recommended operating range of 3.0V to 5.5V.
The 1-Wire bus reset signal is used to initialize the bus and ensure that all devices are in a known state. The reset signal should be asserted low for at least 480μs to ensure a proper reset. After the reset, the bus master should wait for at least 240μs before issuing any commands.
The maximum cable length for the 1-Wire bus depends on the cable capacitance and the quality of the wiring. As a general rule, the maximum cable length is around 100 meters, but this can be extended using repeaters or other bus extension techniques.
