RS232 Control LED without MCU

Thread Starter


Joined Sep 5, 2004

Is it possible without MCU directly using RS232 to control some output device?

At this moment i just only need to control one LED and one Buzzer.
I just need to control 2 output signal. So, hope can design a very simple and no costly design and i just only have serial port TXD and RXD pin only.
I had seen other people did before, they had using MAX232 as a driver to control 2 output but i'm not sure whether their thing is work fine not.

Thank you.


Joined Apr 20, 2004
Without knowing more about the requirement, two switches should be enough to control the LED and buzzer. Just turn them on and of as needed.

RS232 is a means to send data over a distance. Bothe the sending and receiving devices need specialized IC's to function, and the sending would be very difficult without a microprocessor controlling the process.

If more than manual control is needed, a microprocessor can easily turn a couple of transistors or FET's on and off to control the LED and buzzer.


Joined Oct 14, 2005
If you meant to control the devices from a computer using RS232 without any microcontroller, then yes it is possible. There are control lines on RS232 (the ones except TS and RX) that can be controlled from software. Note that the voltage would follow RS232 level for high and low. You'd need switches, like transistors or MOSFETs to switch heavy load.