Hacked Gadgets Forum

October 17, 2006

RS232 Breakout Board

at 5:05 am. Filed under Electronic Hacks

When interfacing a microcontroller to a computer so they can share data back and forth a RS232 port is often used. Most microcontrollers can only output 5 volts and ground (zero volts). What’s the problem you ask? Well have a look at the chart for the mark state. That’s right true RS232 requires a negative voltage to indicate mark. One good thing is that computer manufactures have been sliding the standard for many years now so most systems will accept 0 and 5 volts however this is not guaranteed to work on all systems.

So what can be done without adding different supply voltages and complex switching circuitry? The answer to this lies in a cool chip made by Maxim called the MAX232, it uses a few small capacitors and an on-chip charge pump to create the +12 and -12 volts needed for true RS232. For a simpler circuit that does not need the charge capacitors look into using a MAX233.

David at Volunteer Lab Rat has designed a small circuit board that allows the RS232 level changing circuitry to be placed on a small board that can easily be connected to the microcontroller. The below picture is before and the top picture is the after picture using the RS232 module.

“I hate having to many unneccecary components on my bread board. I often use a serial interface in my PIC projects, and I’m fed up with building the interface using the MAX232 chip every time on the bread board. Therefore I’ve designed a small and very simple RS232 breakout board.”