universal serial PC interface


Posted on Feb 6, 2014    8246

Well, I guess every hobbyist some when comes up with ideas of controlling or measuring something with a PC. Of course the idea is tempting, there are so many easy-to-learn program languages available for PCs today that almost everyone can write the software to switch on the light when he is on vacation, to control these cute little toy robots or t


universal serial PC interface
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o measure the amount of rain over the day. So if you are a somewhat advanced hobbyist, the application is only limited by your fantasy (i. e. the sky is the limit). But: How can we close the gap between a few lines of software code and a real electrical signal outside of the computer Of course there are many solutions to this problem, many of them require serious "hacking" to access one of the i/o ports of a computer. (Especially Windows NT4 required very advanced programming skills if you wanted to use i/o ports for non-standard applications). One port that is easy to access from a software point of view is the serial RS232 port (COM1, COM2, etc. ). All modern software development tools support the RS232 port, so its usually no problem at all to send or receive data via this port. What makes the RS232 very unattractive for hobbyists is the fact the data bits are in a serial time synchronous format with critical timing and a relatively complex start/stop-bit overhead. To make it even worse the bit levels are -12V for high and +12V for a low bit, so connecting RS232 signals to a circuit that uses 5V logical levels is not trivial either. Simply forget about connecting the RS232 directly to a relay driver stage or things like that. And that is where this circuit comes in. It converts a RS232 bit stream into standard digital signal inputs and outputs. It even provides you with a couple of 10bit ADCs so you can read analog...




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