Program Arduino Pro Mini from Arduino Uno

Today I was looking at the tiny Arduino Pro Mini on my desk, wondering how can I program it without FTDI programmer. Unlike the more beginner-friendly boards, this little genius had no onboard USB, and my FTDI programmer is missing. That’s when I thought that an Arduino Uno can be used as a USB-to-Serial converter to program the Pro Mini. I researched on the internet and found there main steps to program Pro Mini Using Uno. You can also program your Pro Mini by following these steps->

Step 1-> Removing the Atmega328P

Remove the Atmega328P microcontroller (the long rectangle black colored microcontroller) gently it from the PTH connector if you use PTH Arduino Uno. If you use SMD Arduino Uno, you wouldn't be able to remove the SMD chip, So leave this step if you use SMD Arduino Uno.

Step 2->Pin connection

PIN CONNECTION

Arduino Pro Mini Arduino Uno

RX --------> RX

TX --------> TX

VCC ---------> VCC(3.3v/5v, depending on your Pro Mini)

GND ---------> GND

DTR --------> RESET (For PTH Arduino Uno)

RESET --------> RESET (For SMD Arduino Uno)

Step 3->Choosing the right board

Choose 3.3v, 8MHz or 5v, 16MHz board in Arduino Ide under Tools-> Processor->*Your Board. Select it depending on your board type.

Step 4-> Selecting programmer

Select the programmer to ArduinoISP in Arduino Ide. Go under the Tools -> Programmer-> ArduinoISP.

Step 5->Coding

Write/Paste your code which you want to flash, In my case- I am using a simple blink code.

Step 6->Upload

When you click upload the verbose output will be like this-

Programmer Type : Arduino

Description : Arduino

Hardware Version: 2

Firmware Version: 1.16

Vtarget : 0.0 V

Varef : 0.0 V

Oscillator : Off

SCK period : 0.1 us

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e950f (probably m328p)

Writing | ################################################## | 100% 0.28s

avrdude: 924 bytes of flash written

ETC....

then at end it will show

Reading | ################################################## | 100% 0.21s

avrdude: verifying...

avrdude: 924 bytes of flash verified

And Congratulations, You have successfully flashed a code in Arduino Pro Mini using Arduino Uno

Troubleshooting

If code not uploading or showing a uploading error, Check the pin connections properly and if still problem exists, Try to change the boards processor from Tools.

If you are using ATmega328p (3.3v, 8MHz) change it to ATmega328p (5v, 16MHz) and then try uploading the code.