Take the 2-minute tour ×
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It's 100% free, no registration required.

I was looking for a cheapest possible option to get arduino and wireless comms for a dimmable light and come across this ebay item when searching for Arduino Nano clone. It has no usb port so how can it be programmed?


I have discovered that there is a new device called "Arduino Pro Micro" which is similar to Pro Mini and Nano but have usb port in-built. The best thing is you can buy Pro Micro for under 4 euros! Excellent for a dimmable LED light...

share|improve this question
You did say "wireless comms" - using an XBee (pair) will allow you to program the pro mini over-the-air. Some hacking/circuitry is needed to effect a reset when the TX/RX is used this way. I'll post it as a full answer if you think its relevant. –  Ron J. Jan 18 '14 at 13:51
It certainly would be nice to be able reprogram over the air, not sure if xbee is a good option as I remember it's not that cheap. But if there are cheap xbee clones that would be great! –  DominicM Jan 18 '14 at 14:40
What is the difference between NRF24L01 (2.4GHz RF) chip and XBee? NRF24L01 chips seem to be dirt cheap at 1 euro, XBee is at least 6 times more expensive... –  DominicM Jan 18 '14 at 17:03

2 Answers 2

up vote 15 down vote accepted

It's similar to an arduino but with the USB to UART converter chip removed to be cheaper. In order to program it you have to use an external converter and connect it to the Rx/Tx pins.
Please note that these boards don't use a crystal as a clock source but a 16MHz resonator which has higher tolerance (0.5%)

enter image description here

You'll need to get an external USB to serial board (or cable), like

enter image description here

Note that there are two "versions" of USB to serial boards. One version outputs Tx pin to Tx header and Rx pin to Rx header and the other version outputs Tx pin to Rx header and Rx pin to Tx header.

If your board outputs Tx pin to Rx header and Rx pin to Tx header (the signals are already crossed) then you should connect Rx of the USB board to Rx of Arduino, and Tx of the USB board to Tx of Arduino (like shown below)

enter image description here

If your board outputs Tx pin to Tx header and Rx pin to Rx header then you should connect Rx of the USB board to Tx of Arduino, and Tx of the USB board to Tx of Arduino (cross connect like shown below)

enter image description here

share|improve this answer
Exactly what I wanted to know! Thanks. Also edited the question as judging from the down votes maybe it sounded like a shopping question. –  DominicM Jan 18 '14 at 0:36
I notice from the image it says mini Arduino Pro, it's a bit confusing. Is it the same as Nano? –  DominicM Jan 18 '14 at 0:38
Arduino's web site provides Programming Tutortial [ Guide to the Arduino Mini](arduino.cc/en/Guide/ArduinoMini) it expands on alexan_e, detailed answer. Notice the CAP in-line between the DTR and RESET. Otherwise you will need to time pressing the Mini's reset button –  mpflaga Jan 18 '14 at 2:38
I actually found a better option accidentally, see edit. –  DominicM Jan 18 '14 at 3:47
@Matt You are correct, I download the images from the Internet and didn't notice the mistake. I'll fix it asap. –  alexan_e Mar 9 at 17:53

Nano vs Pro-Mini

What you have looks more like a Pro-mini than a Nano

enter image description here

Note the MOSI, MISO and SCK annotations in pale blue on pins 11,12,13.


As well as using the serial-port (via an off-board USB to serial adapter) to program the Arduino-Nano, you can also program the on-board Atmega168/ATmega328 using ICSP. You need a programmer but you can use another Arduino for this (using the Arduino as ISP sketch), a bus-pirate or other devices.

Arduino pins 11,12 & 13 are MOSI, MISO and SCK. You also connect reset ("RST"), VCC and GND.

enter image description here
Typical AVR ICSP connector

The Arduino IDE can be, relatively easily, made to recognise "Arduino as ISP" and "buspirate" as options for the "programmer" menu. The IDE uses avrdude to upload sketches, current versions of avrdude (as included in the current IDE) know all about the bus-pirate and several other devices that can be used as programmers.

share|improve this answer
Thanks. In the end I went with the easiest option by far, see edit. –  DominicM Jan 18 '14 at 3:49
DANGER- the Pro Mini in the image with this answer is something other than the Pro Mini sold by Sparkfun 2/15... sparkfun.com/products/11113 AND THEY SEEM TO HAVE "flipped" THE CONNECTOR BETWEEN THE TWO VERSIONS! (What were they thinking?) Look closely at the labels on the pin positions in the images at the Sparkfun page and here. –  Sheepdog Feb 2 at 16:43

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.