app215| Application Note
Application Note 215
2-Wire Communication Using LabVIEW
www.maxim-ic.com LabVIEWTM is a graphical programming tool that is used in the lab to interface with hardware and lab equipment. The graphical LabVIEW program replaces traditional code, which reduces development time by using the pre-made modules, called Virtual Instruments (VIs). LabVIEW has serial VIs that communicate to the serial port on a PC. These serial VIs can be used to communicate with a 2-wire device using a DS3900 that accepts data and commands from the serial port and converts the information to 2-wire protocol. This application note provides an example showing how LabVIEW can be used to communicate with 2-wire devices. The LabVIEW example VI can be downloaded from the Dallas Semiconductor FTP site. The LabVIEW software package is required in order to run the LabVIEW example VI.
INTRODUCTION
HARDWARE REQUIREMENTS
The only hardware that is required to use the LabVIEW example VI is a DS3900. Although, if a customer application board has a means to communicate 2-wire, the DS3900 is not needed but the LabVIEW example VI may need to be modified. The DS3900 provides a way to communicate 2-wire using a PC's serial port. The DS3900 utilizes a MAX3223 RS232 transceiver to translate the serial port signal levels from 12V to voltage levels for a microprocessor. The microprocessor is then able to communicate to the PC by using its universal asynchronous receiver transmitter (UART). The functional diagram for the DS3900 is shown in Figure 1. For more information, refer to the DS3900 data sheet.
Figure 1. Functional Diagram
Vcc
DS3900 Serial Communication Module
Vcc 4.7k 330 LED Pulse
NC MAX3223 Transceiver
R2in R1in T1out T1out R2out R1out T1in T2in
2.2k
Switch
4.7k
Microprocessor
RESET Serial Comm Pulse (P3) SDA (P11) SCL (P10) P1,P2, P4-P9 8
PC
DTR Tx Rx NC
DB9
2-Wire Interface 8 General Purpose Digital I/O Signals
LabVIEW is a trademark of National Instruments.
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