Tidied up a bit!

Last Tuesday and this Tuesday a few of us cleaned up the space and rearranged things a bit.  The goal was to have more workspace for the Arduino Day workshops, and to have things on display that were more representative of who we are.  We installed a few shelves to store projects-in-development (that don’t fit or we don’t want to put them in our lockers or offices), as well as to show off some completed projects.  The shelves are a bit bare right now, but we’ll fill them up soon enough!  Here are some pics to show what the place is like right now…

The lounge after the 2015-03 cleanup.

The lounge after the 2015-03 cleanup.

The electronics bench after the 2015-03 cleanup.

The electronics bench after the 2015-03 cleanup.

The board room after the 2015-03 cleanup.

The board room after the 2015-03 cleanup.

The workshop after the 2015-03 cleanup.

The workshop after the 2015-03 cleanup.


from on March 25th, 2015Comments0 Comments

Join us for Arduino Day!

Arduino Day 2015

Coming up on March 28th, is Arduino Day!  It’s a worldwide celebration of that little blue board that we all know (or have possibly seen, or maybe you haven’t…) Regardless of your skill and knowledge level with Arduino boards, we will have something fun for you.

A full schedule of events has been posted here…

All day: Workshop time – Work on your project, get help on hardware and software…

We will have a few spare boards to work with, bring your computer and have some fun!

Come by and visit, stay for a while, stay for the day! Join us for a seminar, meal or snacks…  We will have the doors unlocked all day.  Bring projects you’ve worked on in the past, projects you’d like help on, or ideas for projects we can work on together!

from on March 14th, 2015Comments2 Comments

Beaglebone Black PMIC for battery backup

One of my Interlock projects has been to explore the capabilities of the Beaglebone Black’s built-in Power Management Integrated Circuit (PMIC) that gives the BBB a pretty useful feature; charging and operating off of li-po batteries. If you look at the BBB board, you will see 4 through-holes behind the 5v plug. These are break outs for the PMIC and can be used to hook up to a battery.

beaglebone with sparkfun battery

Having a battery connected to your board gives you the ability to do things like making a UPS for you beaglebone so in the case of a power loss, it can politely shut-down, run a custom command, or just continue running for as long as the battery can charge it.bbb_pinouts


In most of the use cases, you’re going to find a lithium polymer that can produce around 3.7V which is under the BBB’s 5v requirement. 3.7V will work fine to power the board but of course your 5V USB port will not work while on the battery. Sparkfun has a few nice ones that have the voltage protection circuits built in to help limit the risk you brick your li-po.


There are 4 pins we’re talking about:bbb-batt-srm

  • TP5
  • TP6
  • TP7
  • TP8

You can see in the diagram what each pin-out is. Li-po’s are riskier than some batteries because they’re known to explode in some cases of over powering. A temperature sensor that is designed to check how hot the battery is getting and decide how to handle it, is built into the PMIC in case your battery doesn’t have this capability already(many do). The directions below are going to show you how to jump this temperatur check with a 10k resistor, which is not recommended if you value your home or hackerspace. If you don’t trust the battery you’re charging, I’d suggest looking into accurately reading the temperature from your battery. My Sparkfun batteries do no break out the temperature sensor so this wasn’t plausible.


  • jumper pins TP5 to TP6 (or use an SMT zero ohm resistor)
  • connect a 10K resistor between TP7 and TP8
  • Install a JST connector on TP6 and TP8
  • Connect your battery into the JST connector

With a little luck and the correct battery, you should be in business. You’ll need to let your battery charge before you try and yank the power cable from it. In the mean time, you can query the status of the battery via the i2cget command built into the OS.


The PMIC is accessible using I2C and the builti-n OS for BBB has a simple command line interface to query its state. The following command will tell you whether or not battery is plugged in:

i2cget -y -f 0 0x24 0xA

This will return information that contains this:

0 device 0x24
On battery power only? 0
STATUS: r[0xa]=0x88
Push Button = 0
USB Power = 0
AC Power = 1
CHARGER: r[0x3]=0x1
Active (charging) = 1

“Active” refers to whether it can recognize the battery you have plugged in.  You can also read this state to detect a power failure and automatically failover. If you’re using the default OS for the Beaglebone Black (the one that comes pre-installed), the OS will automatically shut itself down in the case of a power loss. You’ll want to either install another OS, or disable that service if you’d like to change how long the battery should stay online.

More info

A decent amount of research went into this simple project. There are a ton of warnings and caveats that I’m not going to cram into this blog post (i2c address is read only, pin-outs are not a standard size, beware of jumping the resistor next to the pins). You can find out more information here:

Thanks to Alex for finding a fatal flaw in the 10k resistor I was using.

from on March 2nd, 2015Comments1 Comment