#01, M1S: Four-line RS232 Port


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 this Tibbit with the "C" device #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 the RS232 Tibbit with #20 (9 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. Red LEDs are connected to TX and RTS lines. Green ones are for RX and CTS. All LEDs are buffered (with logic gates) and light up for the LOW state of control lines.