December 18, 2014

How to upload code to Arduino Pro Mini 3.3V with FT232RL USB To Serial Adapter


So yesterday I got my tiniest Arduino, an Arduino Pro Mini 3.3V 8Mhz based on Atmega328. It is only 18x33 mm, so really tiny compared to Uno:

As you can see it doesn't has any usb connector, so I also ordered an FT232RL USB To Serial Adapter to be able to program it. It's available on ebay in kit with the Pro Mini only for $7 with free shipping. That sounded cool, but after I received it I  realized what the Pro stands for: I just couldn't find any step by step guide about how to connect the Arduino with the FT232RL.
An other important detail: there is two version of Arduino Pro Mini. One has a 16 Mhz processor and operates on 5V like the normal Arduino UNO, the other one has a 8 MHz processor and operates on 3.3V. I got the second one, because I want to use it with a cheap Wifi modul (ESP8266), which operates on 3.3V.


Fist of all the FT232RL has a solder pad to change the power supply between 3.3V and 5V. The first step have to be to change it to 3.3V, otherwise the Pro Mini can be damaged!
After changing to 3.3V, the wiring is easy as seen in the following picture:


It's pretty similar to the other Arduinos, just start the Arduino software, select board type (in my case: Arduino Pro or Pro Mini (3.3V 8MHz) w/ ATmega328) and upload the code. I first uploaded the classical Blink program, and it runs without a modification (first I was unsure if it also has a build in led on pin 13, but it does and it blinks like charm).


It is easy to use this small Arduino, I'm looking forward to use it projects where size matters. I have plans about an Arduino based lasertag system and home automation projects, where with the ESP8266 wifi module it can be a cheap and powerful combination. 
Btw you should use female-female cables or usb extension cable to avoid solutions like mine:

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