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Article: Serial port tests digital circuits.
- Article from:
- EDN
- Article date:
- June 25, 2009
CopyrightCOPYRIGHT 2009 Reed Business Information, Inc. (US). This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Yury Magda, Cherkassy, Ukraine
Edited by Martin Rowe and Fran Granville
A PC's serial port provides signal lines that you can use to read voltage levels of digital circuits. You can use the port to test digital TTL (transistor-to-transistor-logic)-level circuits. You just need to convert the TTL levels to RS-232 voltages, and you can add a multiplexer to increase the number of signals that the serial port can sense.
The circuit in Figure 1 uses a MAX232 IC from Maxim (www.maxim-ic.com ) to convert RS-232 voltage levels to TTL levels (Reference 1 ). A 74HC4051 from Texas Instruments (www.ti.com ) lets you select any of four digital inputs and ...