Loading Program to Arduino Pro Mini

Arduino Pro Mini is a compact but powerful Arduino board. Being designed with the idea to minimize the cost, the on-board USB to UART chip is taken out. leaving the board with pure ATmega microcontroller, voltage regulator and reset button. Yes, it’s lower cost compared to the typical Arduino Duemilanove orArduino Uno.

We started to carry this tiny little board early of Feb 2012. You can get it from our web-store here, cost you less than RM60.00 and you will get:

  • ATMEGA 328 and pre-loaded with Arduino Duemilanove Bootloader
  • A reset button
  • 5V voltage regulator, reverse polarity protection
  • 16MHz Crystal
  • On board Power LED indicator
  • A programmable LED (Status LED), D13 as on Arduino board.
  • Pin label is compatible with Arduino

The pad is extended out, you can choose to solder header socketstraight header pinRight angle header pinturn pin, etc. Totally up to you 😀 Be creative.

Now the problem is how are we going to load the program that you wrote in Arduino IDE into this PRO Mini? There are a few methods, we will discuss the options available.

Arduino PRO Mini Bootloader pin

1st, you will need to extend the Arduino PRO Mini booloader pin out. I am using Right Angle Header pin, you can use straight header pin. And you can solder from bottom or from top 😀

Arduino Pro Mini Bootloader pinout

Arduino Pro Mini Bootloader Pin out. Reset pad have a “GRN” label at the side, indicating Green.


I will solder from bottom with right angle header pin as shown.


Here you go, Arduino Pro Mini with the bootloader pin extended out using right angle header pin. You can use straight header pin to extend the side pin out and use it on your project or on breadboard.

UC00A Rev 2.0


Cytron will be offering UC00A Rev 2.0 soon, but since it is still under development, we will skip it. Just for your early information, UC00A Rev 2.0 will have the socket ready (header socket) for you to easily plug into Arduino bootloader pin. I will update this article once it is launched.

UC00A Rev 1.0


For the time being, let’s look at the alternatives available. UC00A is a great product, USB plug and play, it will convert USB to UARTdriver is compatible with Windows, Linux and Mac OS. Once it is installed, it will become a virtual COM port. Arduino is using COM port to load program via bootloader method. Install the driver first and do also download the Arduino IDE from here. I am using Arduino 1.0. Let’s look at the interface. UC00A have extend the extra UART pin to the side of the PCB, you can solder 2×5 header pin.


you can solder from bottom or from top, is totally up to you, I am showing soldering from top, I will use it from bottom.

UC00A with 2x5 header

So when you use it, it will become something like this, you will need female to female jumper wires.


Or, you can use Right Angle Header pin. What we actually need from UC00A are:

  • 5V (+)
  • GND (-)
  • TX
  • RX
  • DTR

We are short of one pin from the ready solder socket if you notice, we are short of DTR, you need to extend it out from the side PCB pad. DTR on UC00A is right beside DSR next to RX pin at the side pad.


OK, good! We can connect the UC00A to Arduino PRO Mini 🙂 So what is the connection and how to connect it?

UC00A             Arduino PRO Mini Bootloader

5V (+) ————– VCC (5)

GND (-) ————– GND

TX ——————- TX0 (TXD)

RX ——————- RXI (RXD)

DTR —————— RESET

Most likely you will need to use female to female jumper wires.

and here is my connection.

DSCF6213This is using 2×5 header pin.

DSCF6229Here is the connection at Arduino Pro Mini

DSCF6224Here is the connection if you are using Right Angle Header pin to extend the DTR. (Don be confused, just make your choice, either use this or use Header pin, I just show both methods)

Plug UC00A to the computer, do install the driver following the guide. Now, that is the hardware part of using UC00A, let’s take a look at hardware/interface if you are using UC00B.


UC00B is another type of USB to UART converter, low cost and easy to use as UC00A, but it is only USB 1.1 specification and the driver only support Windows, sorry to LINUX and MAC user. Nonetheless, I am sure many are using it. If you have UC00B, it will be easier as the needed pin to interface with Arduino Pro Mini is already brought out 🙂 Use five female to female jumper wires, connect at follow.

UC00B             Arduino PRO Mini Bootloader

VCC  —————– VCC (5)

RXD —————– TXO (TXD)

TXD —————— RXI (RXD)

DTR —————— RESET (this is the pad lable as “GRN”)

RTS —————— NC (Not Connected), ignore this pin

GND —————— GND

Here is the connection using Female to Female Jumper wires.

DSCF6233Connection on UC00B

DSCF6235 Connection on Arduino Pro Mini (bottom view)

Plug the UC00B to computer, do install the driver following the User’s Manual.

Please bare in mind, you only use either UC00A or UC00B, choose only 1, don’t go and get yourself both UC00A and UC00B 🙂 I show you both methods because you have options.

The above connection also applies to:

  1. Rainbow LED Ring V3
  2. ArduPilot Main Board
  3. Arduino Fio (make sure to adjust the UC00A or UC00B voltage to 3.3V)

Download Program from Arduino IDE

OK, the hardware interface is done, is time to download your program. I am using Arduino IDE v1.0 which can be downloaded from arduino.cc, here. As you might know if you have been using Arduino IDE, you will need to find out the correct COM Port. For Windows user, please get it from Device Manager. For other OS, I am sorry because I only have Windows 🙂


Figure shows UC00B is COM59, you should check your own COM port number as different computer will assign different COM number.

Open your Arduino IDE, choose the correct COM port number through Tools –> Serial Port. Now choose “Arduino Pro or Pro Mini (5V, 16MHz) w/ATmega328”. Now you can load the program you like. I have successfully load the basic program of Blink.

Arduino IDE -Blink 100ms

To verify if the new program is loaded, I simply change the blinking rate to 100ms and reload it, It works!


Now, you can supply power to Arduino Pro Mini with external power source via Raw pin and disconnect the UC00A or UC00B connection. It can be standalone.  If you have problem, please come to our technical forum to discuss.

Good luck!



5 thoughts on “Loading Program to Arduino Pro Mini”

  1. Yup, that is where the power come from when you bootload the program into PRO Mini. RAW pin is left unconnected, do refer to the connection diagram carefully.

  2. Are u sure the Vcc(bootloader) is right to connect to the Vcc at Promini?
    How about the RAW pin on arduino?

  3. Is a question or a statement? We have never try that, but looking at the RS232 voltage, I doubt that is possible without proper level shifter.

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