Signal Generatorsvoltage converter

Serial-to-Parallel Converter Schematic Circuit Diagram

This converter may help if just the serial port on a personal computer is free, whereas the printer needs a parallel (Centronics) port. It converts a serial 2400 baud signal into a parallel signal.

The TxD line, pin 3, CTS line, pin 8 and the DSR line, pin 6, of the serial port, are used — see diagram. The CTS and DSR signals enable handshaking to be implemented.

Serial-to-Parallel Converter Schematic Circuit DiagramSince the computer needs real RS232 levels, an adaptation from TTL to RS232 is provided in the converter by a MAX232. This is an integrated level converter that transforms the single +5 V supply into a symmetrical ±12 V one.

The serial-to-parallel conversion is effected by IC1. This is essentially a programmed PIC controller that produces a Centronics compatible signal from a 2400 baud serial signal (eight data bits, no parity, one stop bit). The IC also generates the requisite control signals. If there is a delay on the Centronics port, the RS232 bitstream from the computer may be stopped via the Flow signal (pin 17). This ensures that no data is lost.
The controller needs a 4 MHz ceramic resonator, X1.

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