#01, M1S: Four-Line RS232 Port

A blue M1S Tibbit.

Function: Simple RS232 port with only TX, RX, RTS, and CTS lines

Form factor: M1S

Category: Input/output module

Special needs: [SER], [INT]

Power requirements: 5V/20mA

Mates with: #19, #20, #21 (limited use)

See also: #02, #05


This is a standard "simple" RS232 port. This Tibbit is based on a generic RS232 transceiver (we use Zywyn ZT232F).

For "normal" RS232 applications, this Tibbit has to be connected to the TX and RX lines of the CPU's UART (see [SER]). Planning to use RTS/CTS flow control as well? An interrupt line must be available, too (see [INT]).

Combining Tibbit #01 with Tibbit #19 (DB9M connector) will create a serial port with standard pin assignment on the DB9M:


<No connection>


RX (input)


TX (output)


<No connection>




<No connection>


RTS (output)


CTS (input)


<No connection>

You can also combine Tibbit #01 with #20 (nine terminal blocks). Using #21 (four terminal blocks) is also possible if you can steal the ground elsewhere (#21 doesn't have its own ground line).


There are four LEDs: two red and two green. The red LEDs are connected to the TX and RTS lines. The green LEDs are for RX and CTS. All LEDs are buffered (with logic gates) and light up for the LOW state of control lines.

#01, M1S: Four-Line RS232 Port