Today I’ve been experimenting with the Arduino Mini Pro and μUSB-MB5, two modules that I ordered from www.coolcomponents.com. I recommend Cool Components to anyone in the UK looking to buy modules like this – they sell a lot of Sparkfun and 4D systems components and you can bet it’ll come from cool components a lot quicker than it’ll ship from the States or Australia.

These are not the easiest modules to hook up so I’ve written this post with some pointers for anyone who has taken this route and got stuck. If it helps you please comment below.
The Arduino mini pro is a stripped down version of it’s bigger brother the Arduino Uno (or Duemilanove for older boards). To the best of my knowledge the arduino mini pro is available in 5 volts and 3.3 volts, I’m using the 3.3 volt board so it is necessary to use a voltage converter to power it from a 5 volt USB supply. Also, it doesn’t have an FTDI chip (the bit that converts serial messages from the USB port on your computer).

Sparkfun do sell a module called SparkFun FTDI Basic Breakout Board that might be simpler http://www.sparkfun.com/products/9716. It is time consuming wiring up the µUSB-MB5 but I use it because it has standard header pins so it fits nicely in a breadboard.

What is the 4D system’s µUSB-MB5?

I’ve used these several times over the past few years and cannot fault them. They work very well for breadboarded projects and it is extremely handy here because it has a 3.3v voltage converter on board as well as the FTDI chip to convert messages from the computer to program the arduino. The drivers for this have been downloaded from:

http://www.4dsystems.com.au/prod.php?id=18

It was quite simple to install the driver on a mac; download the dmg, unpack and install (there was a system restart afterwards) the module then showed up in the list of serial devices as: /dev/tty.SLAB_USBtoUART and /dev/cu.SLAB_USBtoUART.

I realise it is not always that simple. I’ve had problems at work before on windows computers, especially back in the days when the arduino would only work on PC COM ports 1-5.

Nightmare, anyway I have recently moved from PC to the mac (tty and cu) and so those days are hopefully behind me.

Test the µUSB-MB5 before hooking it up to the arduino…

I like to check the MB5 is working before mashing the arduino into it so I connected the Tx to the Rx with a piece of wire to check. I could then open up the Arduino software, write a message and have the signal route out of the Tx pin, back into the Rx pin and display back in the arduino terminal window. I was lucky this time – the serial worked first time and it worked with both tty and cu. (being new to the mac I’m not sure what the difference is yet between tty and cu but for now I’m using tty)

Wiring in the Arduino

Now I know the mac and software is alright, I can wire the Tx from the µUSB-MB5 to the Rx of the arduino and the Rx of the µUSB-MB5 to the Tx of the arduino. The connection looks fine on the board however I kept getting the error:
avrdude: stk500_recv(): programmer is not responding

Short term solution: Press the reset button 2 seconds after clicking upload: (this is a solution I found after searching in the forum.)
Click upload, count “one, two”, a short press of the reset button and it works. Hardly neat but at least I know nothing is faulty.

Long term solution: I need to get the DTR reset working so that the Arduino IDE resets the device at the correct time. I eventually found that connecting the Reset pin of the µUSB-MB5 to the Reset pin of the arduino worked (most…of the time).

Technical details

Here is a summary of the Arduino Mini Pro copied for personal reference from the arduino website:

So what’s next?

For tomorrow I want to see how much power is being drawn so I’m going to create a sketch that blinks the LED 10 times then powers down. Using this blog for the code reference:

http://donalmorrissey.blogspot.com/2010/04/putting-arduino-diecimila-to-sleep-part.html

This method was used for sleep. It features complete power down

void enterSleep() {
set_sleep_mode(SLEEP_MODE_PWR_DOWN);
sleep_enable();
sleep_mode();
/** The program will continue from here. **/
/* First thing to do is disable sleep. */
sleep_disable();
}


And it works, Yeah! I will test the current drawn so that I can predict battery life etc and continue wiring up the I2C lines to connect sensors.

I’ve found it’s using:

4.87 mA green LED off
8.62 mA green LED on
0.44 mA power down

If I use a 110mAh battery such as this http://www.sparkfun.com/products/731

110mAh / 0.44 = 250 hours

250/24 = 10.4 days on sleep or a few days of use.

There are ways to make this use a lot less power of course – there seems to be different levels of sleep on the ATMEGA chip, and if I can turn off the dim red power LED on the board this will help a lot. For now, it’s nice to have the arduino hooked up to the µUSB-MB5

Hi there. My name is Alex Baker (Baker) and I’m an interaction designer based in the UK. I create experiences, make life easier and more enjoyable for people by designing products that people love to use.

In my work I use a wide range of software and hardware; open frameworks, processing, Arduino, Adobe creative suite (Photoshop, Illustrator, After effects etc), Lightroom, 3Ds max and many more.

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