DS18B20

Designers who must interface 1-Wire® temperature sensors with Xilinx field-programmable gate arrays (FPGAs) can use this reference design to drive a DS28EA00 1-Wire slave device. The downloadable software mentioned in this document can also be used as a starting point to connect other 1-Wire slave devices. The system implements a 1-Wire master connected to a UART and outputs temperature to a PC from the DS28EA00 temperature sensor. In addition, high/low alarm outputs are displayed from the DS28EA00 PIO pins using LEDs.

This document describes a microcontroller-based 1-Wire® master interface for reliable operation of small, medium, and large 1-Wire networks. This is accomplished using careful impedance matching, intelligent (software-controlled) active pullup, and slew-rate control. Software flow charts are included to assist the user in generating the correct 1-Wire timing for reset pulse, presence detect, write one, write zero, and read time slots using any suitable microcontroller. Scope traces illustrate the timing performance of the driver as well as transmission line effects as they appear with long cables.