How to program Arduino pro mini using Arduino Uno (no need FTDI programmer)

Arduino pro mini which is smaller than Arduino nano board. we use it for more space-saving, small & lightweight project. Arduino pro mini has not any onboard programmer chip so we use FTDI programmer to program it.

Today I am going to describe in this article, If in case you have not FTDI programmer then you can program the pro mini using Arduino UNO board.

Here are two methods by removing the Arduino Uno board’s microcontroller & without removing microcontroller.

Programming by remove microcontroller of Arduino Uno

You need :

  • Arduino Uno
  • Breadboard
  • Header pins
  • Jumper wires ( male to male)
  • Arduino pro mini 3.3 volt or 5 volt ( I am using 3.3v board for demonstration )

Remove the microcontroller Ic from Arduino Uno.

Connect Arduino pro mini to Arduino Uno as described below.

  • Connect Arduino pro mini GND to Arduino Uno GND
  • Pro mini Vcc to Arduino Uno 3.3v ( If you are using an Arduino pro mini 5 volt module then connect vcc to uno 5volt)
  • Pro mini RX to uno RX
  • Pro mini TX to uno TX
  • Pro mini DTR pin to Arduino Uno Reset pin
Connection diagram of programming Arduino pro mini

Now connect the Arduino Uno to pc & open Arduino IDE software

Go to – tools – Board – select board Arduino pro mini

Now go to Tools – chose processor ( in my case it is Atmega 328p 3.3v 8mhz. You have to choose which is you are using )

Now go to tools – port & select your com port where Arduino Uno is connected.

Now upload the code.

Second method without removing the microcontroller from Arduino Uno

Connection :

All connections are the same as the previous method just connect Arduino reset pin to GND & remove the wire from the DTR pin of pro mini

  • Connect Arduino pro mini GND to Arduino Uno GND
  • Pro mini Vcc to Arduino Uno 3.3v ( If you are using an Arduino pro mini 5-volt module then connect vcc to uno 5volt)
  • Pro mini RX to Uno RX
  • Pro mini TX to Uno TX
  • Pro mini DTR no connection
  • Arduino Uno Reset pin to GND

Connection of without removing the microcontroller from Arduino Uno

All software setup will be the same as the previous method

Here is the main thing which we have to do for this second method

when code is uploading just press the reset button of Arduino pro mini.

If you are uploading code to a new Arduino pro mini then I will suggest you, chose the first method because the second method may not works sometimes for the wrong timing of the reset button press.

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