m1wire

(last updated: 2003/08/16)

Purpose: Use a PDA (PocketPC based) to monitor voltages and temperatures using the Dallas Semiconductor 1wire bus.

Overview

The 1wire bus is a serial communications bus which uses one wire (actually two if you include ground/return) to communicate with A/D converters, temperature sensors, I/O ports, real-time-clocks, and EEPROM integrated circuits. The bus was designed by Dallas Semiconductor. The m1wire project provides the ability to monitor 1wire devices using a PDA. The PDA’s GUI displays the voltage measured by the DS2450 A/D converter and the temperature measured by DS18S20 temperature sensors. It can also capture the measurements to a file stored on the PDA. This project is useful when you don’t want to clutter your desk space with several digital multimeters. It is also useful when you need to monitor a portable device for testing (since the PDA is portable).

The system is presented in the following diagram:

The PDA (PocketPm.C) is running the m1wire application. It uses the 1wire public domain driver code for WindowsCE to communicate through the PDA’s serial port to the DS9097U-9 (RS232-to-1wire) adapter. Either a null modem adapter is needed between the serial cable and the DS9097U-9, or the DS9097U-9 can be internally modified.

The main screen shows the four channels of an attached DS2450 A/D converter and up to four DS18S20 temperature sensors.

My Setup:

- PC running Microsoft eMbedded Visual Tools 3.0 (PocketPC 2002 SDK)

- Compaq iPAQ H3650

- iPAQ-to-DB9 serial cable

- null modem adapter (DB9F-DB9F)

- gender changers (DB9M-DB9M)

- DS9097U RS232-to-1wire adapter

- Cable with two wires

- DS2450 A/D converter (mounted on an smt adapter board)

- DS18S20 temperature sensor

Download (see Attachments)

m1wire_doc - Specifications and Users Guide

m1wire - project files for Microsoft Visual Tools 3.0

Note: A program which installs the m1wire application on the PDA is not available at this time; therefore, the application must be loaded using Microsoft Visual Tools 3.0.

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