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DS28E18 Setup Guide for Remote I 2 C and SPI Sensors Featuring the DS2485 It is well established that the I 2 C and SPI communication protocols are designed to be used in short-distance, intra-board communication. This application note discusses the I 2 C and SPI bus extending capabilities of the DS28E18 1-Wire ® to I 2 C/SPI Bridge with Command Sequencer. Specifically, it covers important measures for setting up a long line, e.g., 100m communication with multiple I 2 C and SPI sensors and the benefits of using this device. Introduction The I 2 C and SPI communication protocols are well known to have short bus distances that range no more than a couple meters. Although solutions currently exist for extending these ranges, they are often complex and expensive. The DS28E18 , however, is a cost-efficient bridge-chip device that demonstrates the benefits of using the 1-Wire interface to get the most range out of complex I 2 C and SPI devices such as environmental sensors,

  The design provides a complete solution for the 4 mA-to-20 mA transmitter for #pressure sensor measurements where the supply for the entire circuit is provided by the loop. The circuit has three critical stages: the sensor excitation drive, sensor output amplifier, and the voltage to current converter. The total current required by the circuit is 1.82 mA (maximum) as shown in Table 1. Pressure sensors requiring bridge drive currents of up to 2 mA can therefore be used without exceeding the maximum available loop current of 4 mA. ‹ ›