Connecting a serial port to an Arduino RX pin?


I am planning to make a simple breadboard Arduino that needs to accept incoming serial data. The chip is already programmed with code for this and I am wondering the best way to hook up a serial connector.

Can I just connect to a computer's serial port via GND and RX into the Arduino, or do I need other components for voltage adjustment?


You must have a serial line level converter. The Arduino serial is actually TTL serial, not RS232 standard serial. Most people use a MAX232 converter and wire it up, it will do bi-directional communication with the Arduino (bring up the TX pin and bring down the RX pin with that single chip).

If you want to buy a board you can pick up this guy for really cheap: WARNING: 10-14 day shipping is the reason they're cheap.

Otherwise Sparkfun has the bare chips:

Thanks for that, I thought so :-)

Ok, I have had a look at the original Arduino Serial board, and that does not use a MAX, it looks like it uses some discreets to do the conversion?

Also I only need one way coms, into the Arduino.

You may be able to get by with just a NPN transistor and two resistors. I've been using the below setup for ~6 years on my pan/tilt web cam.


Cheers dude, and thanks for taking the time to attach the pic.

I have previously just used a resistor to drop the voltage for PIC chips and rs232.

I just ordered some MAX232’s but will try your method.


Hey, that's the same CAD system Grumpy_Mike uses!