I bought an Arduino-on-breadboard kit. I have several PCs with serial ports, and now I'm being told I need a USB-to-serial converter. I thought I was ready to start uploading sketches, so how can I do this?

I'm able to understand serial communications and am capable of wiring a MAX232 chip into a breaduino if necessary, but I'm not sure it will work, so to save some time I'm asking, mostly because I was unable to figure it out with Google searches alone.

PS: I also have a stk500, but then I would be out of the easiness of using Arduino sketches and the programming language. I need the fastest route to prototyping/testing my sketches.

  • 3
    The arduino IDE supports the stk500: arduino.cc/en/Hacking/Programmer
    – Gerben
    Aug 12, 2014 at 19:54
  • I would highly suggest you also buy an arduino Uno. The breadboard version is great but the uno board will help you verify the rest of your tools and software is setup correctly
    – benathon
    May 12, 2015 at 11:59
  • thanks for the help guys, will post pics as soon as I have some working prototypes! May 12, 2015 at 19:30
  • @PeterMorensen - please don't make trivial edits to four year old questions, it serves no purpose but to create noise on the overview page. Mar 11, 2018 at 19:13

2 Answers 2


enter image description hereAn RS232 port wired via a level converter (as you mentioned max232) and a 1uF capacitor between RTS and "Arduino reset pin" Getting started with Arduino.

The capacitor is to trigger a reset on the Arduino so the bootloader kicks in and awaits a "Arduino sketch" via the serial port.

Your setup is AKA "Arduino Bare bone".


If your PCs have real RS-232 serial ports (rare these days), you can use those directly. Otherwise, you will need a USB<->RS-232 serial adaptor cable.

Correction: I thought my Arduino did have an RS-232 port, but I was thinking of another board. If your board only has a TTL-level serial port (ie. direct from the ATMega328), then you need either an RS-232 level translator, or a USB<->TTL serial cable. A suitable cable is available from Adafruit (and no doubt, others).

  • 3
    Can you really connect a RS232 (either real or fake 0-5V ones) directly to a ATmega328 UART port? I thought one had to put a level converter in between them (ie. MAX232).
    – Ricardo
    Aug 12, 2014 at 18:40
  • The original Arduino models did have RS232 serial ports and connectors, rather than the USB connector and on-board USB-serial converter of today's boards. Aug 12, 2014 at 21:01
  • 1
    You cannot connect RS232 to an ATmega328 port (successfully anyway) because the polarity is inverted. With RS232 a 1-bit is -12 V (or thereabouts) and 0-bit is +12 V (or thereabouts). See <en.wikipedia.org/wiki/RS-232>. In other words, a one bit is a lower voltage than a zero bit. Even the 0-5V ones are still going to have inverted logic. SoftwareSerial does have an "inverse_logic" argument on the constructor which might help if you had the 0-5V serial input.
    – Nick Gammon
    Aug 10, 2015 at 6:20

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