Saturday, March 9, 2013

Building an Arduino Pro / Arduino UNO (with TechDuino)

I wanted to build a 3.3V microcontroller development system for a long time. This is because most newer sensors and other  devices are working on LVTTL voltage levels. Now,5V systems are becoming obsolete and even 1.8V systems can be seen. Arduino is an open source microcontroller development system which uses Atmel ATMEGA series microcontrollers. As I found out they can operate at 3.3V at 8Mhz. As AVRs(let’s call them as AVR) are running 1MIPS per 1Mhz,you can get 8MIPS even at 3.3V. Quite impressive isn’t it ?
There is a board called Arduino Pro which is designed to run at 3.3V specially. But the majority uses Arduino UNO which seems to be the most popular Arduino board in present day. When I look for DIY Arduino boards,I found out about the TechDuino which is a custom built Arduino UNO clone with through hole components.
You can buy a prebuilt Techduino or as parts( PCB,uC…etc) separately from the TechShop. They are delivering the items by post and they are nicely packed. The service is awesome in all ways.
As I needed to build an Arduino Pro (as on a Arduino UNO layout,a hybrid of course), I ordered some PCBs for TechDuino and a Arduino Pro(3.3V/8Mhz) bootloader preloaded ATMEGA328 from Techshop. For a PCB & an uC IC is costs Rs700 (US$5.5) and it’s really cheap. Then I had to find a 3.3V voltage regulator and I picked AMS1117-3.3 voltage regulator (You can use any other 3.3 regulator like 7833 or even a LM317 with a proper circuit).I had a bunch of them got from ebay sometime ago.I also got some resisters,capacitors,LEDs,connectors from my stores.
This is the TechDuino PCB I got.
Then I soldered the components. You can refer the parts list & buidling notes from here.  I had to do following changes to make it a 3.3V system and suite my other needs.Please compare the changes with the coloured arrows in the picture.
  • Replaced the 7805 with my AMS1117-3.3 (Please note it has different pin out and a surface mount IC,So you have to compare with 7805 pinout and solder using wires or so) [RED]
  • Opted out the DC power jack and soldered a connector to it. [PURPLE]
  • Used a 8Mhz Crystal not a 16Mhz as for the 5V system. [BLUE]
  • Used 100 Ohm resistors in series with LEDs [GREEN]
  • Didn’t have a 4pin push button switch,just used a jumper to make a ground connection as needed [ORANGE]
  • Shorted 3.3V & 5V pins in the board,so that both 3.3V & 5V lines will also have 3.3V
After this you can use a CP2102 USB to UART board to connect this to the computer (You may purchase it too at TechShop when you get the PCB…etc).If you have any other please refer my previous post.. Please only connect RX,TX,GND,Reset pins to the programming header. Then connect 5V pin to the external power connector Red wire(shown in purple arrow) if you power the Arduino with USB or else you can power it with external source using the external power connector.
Then download the Arduino IDE from site. Here I’m using Arduino IDE 1.0.3 version. You have to select Tools->Board as Arduino Pro 3.3V/8Mhz.You also have to select the serial port which the Arduino is connected to. The prebootloaded ATMEGA has a pre programed program to blink the LED at Pin13.So,the LED will start to blink when you supply the power.Use an example like led blink on Arduino IDE to test that the everything is working correctly.
Happy Arduinoing!!!! Open-mouthed smile I will show how to build a Arduino powered webserver in my next post Winking smile


  1. AWESOME!!! will follow this!!! can u do me a little favor. can you upload a pic of the PCB side of the board ;) then i can DIY the board too :D
    And what is a bootloader?

    1. it is just like a dev board machn,but open standard called arduino.they are on that site too.

      you can find about what is a bootloader here:

    2. I know it is a dev board. I just wanted to see the Printed Circuit. To copy!!! And the bootloader link is dead!!!

    3. That a PIC bootloader,the link is dead and there is a backup link below it :D I just gave it to show about bootloaders,

      Arduino bootloaders are available with the Arduino IDE (the link is on this post)

      Original PCB Layout:

      This is a simplified version,only keep the ATMEGA328 and remove other ICs including USB interface


      You can find the devices to remove using this :D

  2. ela ela machn.... I will send you my progress with this device once I begin to work with it.... :)

  3. I tried this.. But unfortunately I cudn't get the Print out of the PCB layout, The print out guys r refusing to print it in the heat toner transfer paper. .. any suggestions?

    1. You can print on normal A4 paper,iron it and put in water to remove paper not the toner,then the toner will remain on the copper board.

    2. Bro... Superb IDEA. Maxxa.... I'll try it & let u know.. Thanks again... :D


    4. I have used that way to do pcb for surface mount chips too.
      you may ask the printing people to print on magazine paper too.
      Most them are only printing on A4.

    5. use a photo print paper and peel off the paper after ironing. a paper will cost about 30 LKRs

  4. can u upload the pcb side of the board

  5. Lakduino UNO R4 is a nice & smart Sri Lankan product made on a high quality PCB by LankaTronics. It is USB supported board with Windows 8 supported chip specific to Lakduino making it a non-duplicate product of the original.

    You can buy original Arduino from local agent Aptinex.

    If you need to make your own UNO board, consider the PTH board designed and published by Arduino at
    They provide all the schematics required and the parts could be bought from LankaTronics.