Analogue to Digital Converter

  
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This circuit is a simple 8-bit analogue to digital converter circuit which is connects to PC serial port. The circuit is based on TLC548 A/D-converter chip (might be hard to get nowadays, Texas Instruments makes this IC), which is an A/D-converter with serial output. The output of the TLC548 is not directly suitable for standard serial data recept
Analogue to Digital Converter - schematic

ion, so this circuit uses serial port handshaking lines in a nonstandard way which enables the communication between computer and converter chip to be implemented with as few components as possible. The circuit takes all the power it needs from PC serial port. A generally asked question is "Can I Connect a Serial A/D to My Computer`s Serial Port ". The answer to this question is yes, but there are simpler ways to interface to a computer. To begin with, the computer`s RS-232 port uses higher voltage levels that are incompatible with most ADC`s TTL/CMOS logic. Another problem is that the computer`s RS-232 serial port is asynchronous, which places a few more requirements on the communication, including some additional handshaking control lines. Also, with the RS-232 serial port, you must set both ends of the link to the same baud rate. The A/D converter`s serial port is synchronous; thus, its handshaking requirements are minimal and it only requires one wire for clock and one or two wires for data. If you are truly determined, you can bit-bang using the RS-232 port`s handshake lines. This circuit uses this control method. The voltage conversion of signals from RS-232 port to IC input pins is done using a combination of series resistors and the internal input protection diodes in the IC. The output of this A/D was able to directly output signals which seemed to be detected by RS-232 port (the output of the chip does not meet...



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