I apologize in advance, because there is a lot of tutorials out there about programming arduinos with another arduino, however I can't find really simple one I could understand.

I have Arduino Uno SMD version and Arduino Pro mini 328. I want to upload sketch to Arduino Pro mini using Arduino Uno in ISP mode (I guess).

I want to know EXACTLY which pins need to be connected and if all I need is Arduino IDE to upload my sketch to Pro mini ?

Thank you for your help.

  • For upload sketch to Arduino Pro mini, unless your code size is really big and run out of space, many people use FTDI style USB to serial board (6 finger nails sized) to download via bootloader. There are tons of tutorial with good diagram. Try search by these keyword. Sparkfun and arduino.cc should have needed info for you
    – EEd
    Commented Aug 22, 2014 at 11:59
  • 1
    @JohnWilliams Thanks for comment. However, I don't want to buy another board. I just want to use my 2 existing ones.
    – Frodik
    Commented Aug 22, 2014 at 13:13
  • How exactly have existing guides and tutorials failed you? Commented Aug 22, 2014 at 14:32
  • @IgnacioVazquez-Abrams Well, I haven't actually found any which would cover exactly my scenario - meaning Arduino Uno SMD and Pro mini 328.
    – Frodik
    Commented Aug 22, 2014 at 16:24
  • ISP via the Arduino is still done the same way regardless. Commented Aug 22, 2014 at 16:43

3 Answers 3


check this tutorial:


Works fine for me (I have a redboard, also with SMD microcontroller). In short this is the pinMap:

UNO BOARD (SMD)    Pro Mini 5V
       GND             GND
       5V              VCC
       RX              RX1
       TX              TX1
       Reset           GRN
  • Just to be sure, RX and TX on Uno board are digital pins 1 and 2, right ? But that would mean, that if I wanted to upload sketch to finished project which would have soldered all the digital pins to other modules, I couldn't use those 2 pins (RX,TX). That was the reason why I wanted to use ISP so I wouldn't have to sacrifice 2 pins.
    – Frodik
    Commented Aug 26, 2014 at 4:25
  • @Frodik - ISP requires 3 pins plus reset, bootloader requires 2 plus reset. That doesn't mean you have to reserve the pins, but it does mean you can't use them for things which conflict. For example, you can use them as outputs from the ATmega to peripherals, as long as spurious operation of the peripherals during programming is not problematic. But you shouldn't use them to read from peripherals which might problematically drive signals onto those pins during the programming. Commented Aug 26, 2014 at 15:53
  • @ChrisStratton But if I understand it correctly, ISP requires different pins than digital 1-13, right ?
    – Frodik
    Commented Aug 26, 2014 at 16:29
  • @Frodik As Chris mentioned, 3 pins are used, these pins are D11, D12, D13. The arduino website shows this arduino.cc/en/Tutorial/ArduinoISP. Remember that a Pro Mini is literally an Uno that got shrunk.
    – Doowybbob
    Commented Aug 26, 2014 at 20:22

Please check this tutorial if you want to upload sketches to Pro mini with Arduino UNO with SDM chip http://www.instructables.com/id/Uploading-sketches-to-Pro-Mini-using-Arduino-UNO-b

  • It is preferable to answer questions directly rather than simply linking to external sites. Adding a summary of the Instructable text, specifically address the question asked by the OP about which pins are involved, would go a long way to helping the the OP, other people with the same problem, and getting your answer accepted. Commented Jul 31, 2015 at 11:47

Following the tutorial on http://www.instructables.com/id/Arduino-Examples-2-Use-an-Arduino-as-a-FTDI-Progr/ I was able to upload the blink sketch to the Pro Mini 5V version with an Arduino Nano. After I tried uploading the sketch that I really wanted to use but got many errors in the IDE I tried a couple more with no luck. I had stumble on another article earlier about using the Arduino Nano to program the Pro Mini http://www.electronicsmayhem.com/?p=31. I had tried that method but with no luck but using the first tutorial & only changing one thing from it with info from the article i mentioned I was able to upload the sketch without any errors. The only thing I changed was I didn't connect the TX from the Nano to the TXI of the Mini.

   Arduino Nano     Pro Mini 5V

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