TTL-to-RS-232 converter

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Contents

This module provides logic-level signal conversion to RS-232 levels and vice versa. Such level conversion is required, when interfacing, for example, an ATMega8 uC via UART with Computer COM port.

This separate board allows not to place converting IC to the main board. User must ensure that output TTL cable length is no more than 20-25 cm (less than 10 cm is better).

Schematics

Below is a schematic capture of the board

New version of schematic of the two-channel RS-232 to TTL converter. This is a converter based on one IC (ST232 or MAX232) and only two inputs/outputs. There are also other schematics with more converters on single PCB.

PCB

Single sided PCB is shown below:

New version PCB of the two-channel RS-232 to TTL converter.

Single sided PCB but for six channels:

PCB of the six-channel RS-232/TTL converter.

PCB mask for TSSOP version

Notice GND traces and pads are shown in purple color.
J1 connector - 5V power for the converter;
J2 connector - TxD/RxD signal line. RxD pin is marked as circle and positioned near the "TxD" caption.

Wiring

The pitch of the connector is 0.100". Connector footprints in OrCad are:

3 pin connector for RS-232 signal

4 pin connector for TTL-COM signal

Wires coloring and pinout of the RTX connector

Device photo

Notice blue and yellow markers which indicates first pin.

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