Are you using parasitic power? If so don't.______Rob
Network weight is limited by the ability of the cable to be charged and discharged quickly enough to satisfy the 1-Wire protocol. A simple resistor pullup has a weight limitation of about 200m. Sophisticated 1-Wire master designs have overcome this limitation by using active pullups, that provide higher currents under logic control and have extended the maximum supportable weight to over 500m.
The pull-up resistor value must be low enough to provide sufficient current through it to power devices on the bus, but not so low that the open drain slaves are unable to successfully pull the data line down to a logic 0 level.Slave devices are typically able to pull the bus line down to about 0.4 volts when faced with 4 ma of pull-up current due to their internal resistance of approximately 100 ohms. Any additional resistance (due to wiring or other devices) will limit this ability even more. This defines what is referred to as the base floor for logic 0 states. As you may have recognized from this the theoretical noise immunity has been cut in half. To only 0.4 volts (0.8 -0.4 = 0.4 volts). Typical values for the pull-up resistor are between about 1K ohms to 4.7K ohms. This sets the current range to between 5 ma and 1.06ma
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