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Description: The ‘must have’ IC for TTL/CMOS projects finally has its own breakout board! This is the RS232 converter IC that is capable of running at 3V and communicating with 5V logic.

We’ve taken the SOIC package MAX3232 and broken out all the pins you need to set up your RS232 to TTL connection. We’ve also included the necessary 0.1uF charge pump capacitors. Also remember that because the MAX3232 operates at a broader voltage range than the 232 (3 - 5.5V) you can use this on both your 3.3 and 5V projects!


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Customer Comments

  • Take this and add an SC16IS740/50/60 (an I2C-based UART), or equivalent, on the back and you got a neat little board to add RS232 to an I2C bus.

    • Alright, I’ll try it, but if it doesn’t work you’re going to have to come to my house and fix it! (Thanks for a great suggestion!)

  • Any chance we will ever see a board like this with a DB9 and a MAX3232 on board? Just about every time I use RS232 there is a DB9 connector somewhere, either on the PC or a device.

  • Very Cool! Now, if you could put LEDs on it for status, it would be perfect!

  • Im looking at using one of these (and an arduino pro Mini) to make a button panel in my wall, which when i push a button sends a string done the RS232 to a controller. can anyone recommend what cable length would be suitable for the rs232 comms? (what would be a max safe distance) assuming i am using a two core screened cable. the whole unit will be powered via 12V on a separate cable

  • OMG - what a HUGE PITA the naming convention used on the pins of this board!! It is a real nightmare to try and remember that R1IN is RS232 but T1IN is TTL/5V!

    I hope you redo this board some day and come up with a more intuitive pin-naming convention. Serial comms is always confusing (who is sending, who is receiving.. ) - Also it would be really super if you brought out the Enable pin as well.

  • You should add more holes for ground connections. If you use this for two RS-232 connections you need to connect 3 wires to one hole. Having 3 holes would make it much easier to wire.

  • Be aware that the datasheet says “The drivers are inverting level transmitters that convert TTL or CMOS logic levels to ± 5.0V EIA/TIA-232 levels inverted relative to the in- put logic levels.”. So, it wont work in serial communication between RS232-ttl (like in beaglebone(3.3V) with arduino(5V) or raspberrypi(3.3v) with arduino). Since it inverts the bits, it will also invert the start and stop bits, messing up with the serial protocol.

    • You’re reading a whole lot into that single sentence from the datasheet, and making some reasoning about the RS232 protocol that I’m having trouble following. As for Beaglebone, check this serial cape that uses the same driver chip, with essentially the same circuit from the datasheet’s ‘Typical Operating Circuits’ section:

    • Most devices do let you play with the start and stop bits if you have the board already. If not you really just need a logic level converter to go from the 5V Arduino to the SBC (the Arduino will read the 3.3V just fine).

  • Is it possible to program the Arduino Pro Mini through this device?

    My project interfaces with anther device via RS232 so I have the MAX to communicate with the other device. Instead of taking my project apart to reprogram it I would like to simply use the external interface. I bought another MAX and hooked an FTDI USB programmer to it. I can see my serial traffic when the project is running but for some reason the Pro Mini doesn’t respond to the Arduino IDE.

    Any suggestions?

    • You should be able to program through it, although I’ve never tried it.

      Start the upload as normal in the Arduino IDE, then push the reset button on the Pro Mini. When the Pro Mini comes out of reset, it will briefly enter the bootloader, and the upload should proceed as normal.

      No guarantees, YMMV, etc.

  • Will this work out-of-the-box with an Arduino Due (3.3v) device? I don’t want to end up frying my SAM3X8E….

  • What is the logic level? is it 3v or 5v? Does it change depending on the supply voltage?

  • Am I reading the schematic correctly? Is this, somehow, dual channel? I’m considering making a ‘serial spy’ that listens to both the Rx and Tx lines of a cable, and transmits them out another converter to a computer, so you can see how the devices are communicating. Dual channel (being able to have two Rx lines) would be awesome.

    • Yup, it’s dual channel, so sniffing RX and TX and dumping that into, say, an FTDI Basic board would be a terrific application for this.

  • During normal operation how much current does this chip draws? I’m I reading correct from the datasheet that it only takes 1 microAmp?

  • What are the dimensions of this board?

  • Does this let me put an RS232 input onto my arduino?

    • That’s what I was going to use this board for. I have to run twisted paired signals about 12 feet.

      • Yes. You put Arduino RX to R1IN, Arduino TX to R1OUT, serial devices TX to R1IN, RX to T1OUT. Then add ground and voltage. Hope this helps.

        • I only found success by experimentation, and very definitely ended up as follows: Arduino TX > MAX T1IN Arduino RX > MAX R1OUT MAX T1OUT > Serial TX (Pin 2) MAX R1IN > Serial RX (Pin 3)

          This using a Mega 2560, FWIW.

        • Shouldn’t serial devices TX not go onto T1IN?

  • This was needed a longgg time ago. Thanks for finally getting around to make it! 3v3 projects will now be able to communicate to the outside world.

Customer Reviews

4 out of 5

Based on 2 ratings:

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must have when working with older devices

Works great, just like you’d expect a MAX3232 to be. Would have 5 stars if it could plug into the programming headder on the Arduino Pros and have holes for the terminal side DB9 connector along with headders for the RX2 and TX2. But this is good, much handier than stuffing DIP in breadboard along with the caps.

Just the ticket for configuring Bluetooth modules

I needed a 3.3v TTL to RS232 converter to talk to my HC-06 Bluetooth modules in order to use the AT commands. Worked great.