Little Helper

If you have read one of my previous blog posts about building a custom Teensy you already know I have been working on a device based on the Teensy design.

Working in my lab with electronics I came across different little challenges once in a while, and noticed that I am missing tools to handle them efficiently. Just a quick list, I am sure you could add various items to the list:

  • What is the I2C address of a chip? (yeah, you can work through the Datasheet but the Datasheets I know don’t have an outline topic for this. It’s somewhere hidden deep in text somewhere)
  • What is the voltage range of the analog sensor in my current environment (take a photo sensor)?
  • Generating PWM or DAC signals
  • Does this circuit do anything?
  • Does this circuit do anything specific?
  • Reading serial output of your Microcontroller/Arduino project

Of course these aren’t any issues that you could not handle with the tools you have. But each of these take time. Checking an IC for it’s I2C address is easy: Connect it to your Arduino Uno, firing up the I2C Scanner sketch and you are good to go. That is 10 minutes minimum finding your Uno, wiring it up, firing Arduino IDE, uploading the sketch. And everything while your workspace is full of components, wires and stuff for the actual project you are working on.

I had been working on wireless sensors for a while that should take the least amount of power possible. You cannot add status LEDs as they draw way too much power. I had those PCBs lying around and had no clue if they do anything. I had to carry my laptop around, connecting it to the PCB to read the serial port to see what it does.

Why, the heck did I learn all that programming and electronics stuff and not using it to solve that issue. I thought of a small, portable device featuring some ports to connect stuff like sensors and other circuits and some menu driven user interface to trigger various modules doing tests, reading data, you get it.


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Building your own custom Teensy

UPDATE (November 24, 2016):

While this blog post still is very popular, it’s a bit old now. It still uses the old Teensy bootloader chip that is meanwhile deprecated and is not available anymore in larger quantities. However, I have been part of the dev team of the new Printrbot Simple 2016 and I have developed the display component which also uses the Teensy. Printrbot made everything open source.

If you are interested in building your own Teensy hardware, have a look in my Behind the scenes report and the Hardware explained report which makes the schematics and PCB available for download. This new PCB features the latest Teensy bootloader chip.

Although the bootloader chip is old that is described here, everything else like routing USB traces is not! Have fun reading it and let me know what you think!

UPDATE (December 15, 2015):

As you are reading this you might be interested in my custom built Teensy project named Little Helper. I made it Open Source under the MIT license including Schematics, Layout, BOM, 3D models of enclosing, and the complete Source Code. Have a look: Appfruits LittleHelper.

UPDATE (June 26, 2015):

Due to popular demand I have created a “reference board layout” and the schematics in EAGLE CAD (7.2) format. I created it by removing all components that were specific to my project. I just left in the Teensy part, the USB-port and a 3.3V regulator and rearranged the components so they fit in a small footprint. I have never produced the board but it should work (also it doesn’t do anything useful) as the components and layout have been working flawlessly in my own application.

This should speed up your development time for your own project. The board layout contains a switching regulator for the 3.3V which might be overkill if you are running your board of an USB-port as the provided regulator is mainly used with LIPO battery based projects and is hard to hand solder (I use a reflow oven which works quite well with QFNs). Use a simple LDO if you are just running your board with USB power. I have left the board layout for the switching regulator as it has been quite hard to get a good board layout with nearly no noise (switching regulators tend to be very noisy due to it’s nature) and should get you up and running quickly if you intent to do a LIPO-based project (of course you will need to add a LIPO charging circuit which can be found for example in Sparkfuns Power Cell product (see board and schematics for details).

All parts have an attribute named MPN for Manufacturer Part Number and MF for manufacturer. This way you can just use EAGLEs BOM-ULP script to export a BOM that you can directly upload to Mouser of DigiKey to get your parts.

Please note: Don’t order the MINI54TAN at DigiKey or Mouser. You will need to order the MINI54TAN at as this IC contains the core Teensy functionality!

You can find the EAGLE board layout and schematics in our Github repository: Custom Teensy 3.1 board layout and schematics. Please make sure to read this blog post before using parts or the whole “reference board” in your own project as there are quite a few things to consider which is largely documented and described below.

If you are reading my blog you might know that I really love Teensy. Teensy is an ARM powered very little Arduino compatible development board. It does one thing so damn good and I think that is very important for a development board and one of the keys to the success of Arduino: Easy programming. You do not need to connect wires and fancy boxes (JTAG programmers), just connect with USB and click on the program button.

But I am not a big fan of using development boards within final products. Although Teensy is really small it’s too high to pack two PCBs together. Using headers for easier soldering and it gets worse. If you really want to build small products you will often have to build your own PCB. Paul Stoffregen, the creator of Teensy enables these efforts by providing the bootloader MCU in his own store. They are very professionell. I had a few issues with german customs and they immediately sent out new ones and I received a refund for the first package that did not make it through.

Of course it’s not Pauls business model to help you out building your own Teensy, although he was very helpful in the forum. You will have to rely on the great Teensy community or blog posts like this one.

As I had a bit of trouble to get my custom Teensy board up and running I will try to give you some advice on how to build your own. (more…)

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Teensy – Arduino on Steroids

I love the Arduino Eco-System. Although I do not really like the IDE, the whole system is awesome. And it allows to quickly prototype ideas. And, as everything is Open Hardware, it also allows you to build your own PCBs with the same components used by Arduino. I am not in the business for creating a large-scale electronics product. But it’s very important for me that I could.

While working on my DIY Home Automation System I noticed some limitations with the current Arduino Hardware Offers. I have created my own Atmel 328p based PCB for my sensor nodes. The Atmel 328p is the MCU that drives Arduino Uno, Nano, Micro Pro, Sparkfuns Redboard and various other Prototype Systems. This MCU is quite fast (up to 20 MHz), can be run on batteries for a long time (if you care about your current consumption) and is easy to use program with the Arduino IDE. But there are limitations. You only get about 2K SRAM and 32K of program memory. That is enough for devices that only connect to a few sensors, driving a few motors, etc. But it’s not enough for more complex projects.

My DIY Home Automation Network needs a hub, that acts as a bridge between the Internet and the sensor nodes. Sensor Nodes are using nRF24L01+ Radio Modules. The Hub also hosts such a radio module, but has to send the signals in to the cloud. Although I wanted to have nice devices in the end I tried an Arduino Yun as a hub. The hub does not have to be very pretty as it will be placed in a small room that is not exposed. A small enclosure will do it. Arduino Yun is a great device that hosts both an Arduino MCU and a full-fledged Linux on the same device, connected with a bridge. Using the bridge you can run shell commands from the Arduino MCU on the Linux side and receive the results. You do not have to build a whole HTTP-client, as Linux already has one. I have written a small tutorial about that: Running Node.js on Arduino Yun.

All of that worked fine – in the lab. Using the sensor networks in the wild (well, in my house), I found it very difficult to debug the system. In order to save power the nodes do not have any LEDs, Display, whatever. I added some LEDs to the Arduino Yun that showed it’s state and if sensor data came in. But all in all it did not really help. I found sensor data in the cloud, but not from all nodes. And I could not really see the routing in the nRF24L01+ network. Attaching displays to the sensor nodes has not been an option due to power restrictions. I had to add a display to the hub. That would give me the option of adding some sort of user interface to it. But Arduino Yun only has 2K SRAM, and adding a display and it’s quite large driver code I ended up with not enough SRAM left. I could optimize everything so it perhaps would fit, but I would not have any room to add a UI to the hub later on. I have been quite disappointed about this limitation. I think the Yun should have built with a beefier Arduino-MCU. It should be possible to drive a display trough the bridge from the Linux side, but that would be way to slow. Although I really liked the idea of the Yun, it did not fit my needs.

Teensy is here to help

Searching for an Arduino Compatible small device Google with tell you to have a closer look at: Teensy. Teensy is just an amazing piece of hardware, created by Paul J Stoffregen. Paul did an amazing job with Teensy, especially the latest version 3.1. Teensy ist very small. If you find an Arduino Nano or Micro Pro small, you will be amazed how small Teensy really is. And it’s very, very powerful. Teensy features an ARM Cortext MPU with 64 KB SRAM and 256 KB Program memory. That is a lot of space and enough to do a lot of cool stuff. What I really love about the Teensy is how bootloading it is solved. I had a few issues with programming Arduinos. Teensy features a tiny uploader software, that is either triggered by the Arduino IDE or by pressing the reset button on the device. And uploading new code always worked. I really love that. Just install the Teensy Hardware Plugin in your Arduino IDE 1.0.x (it does not support 1.5.x at the moment) and you are good to go.


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A DIY cloud centered, iOS controlled, Arduino based Home Automation System – Part 1

Wireless Node Prototype

There is a lot of buzz around things like “Internet of Things”, “Home Automation”, and “Smart Homes”. One reason for buying into commercial home automation systems is energy savings. At least that is often the main marketing message for commercial products. That is not true, as recent studies found out, and it is not my main motivation to build such a system.

A lot of commercial systems use Bluetooth (Low Energy) Systems zu drive their home automation solutions. You have a device, and an App that is connected to this device to control it. Sometimes, you have an array of devices, that are connected to a hub often with Zigbee based Mesh networks (so your Smartphones App only needs one connection). One example for that is Philips Hue Light System. Apple realized this is a problem as no one wants 10 Apps to control different aspects of their home and introduced HomeKit. While this really sounds interesting on iOS-Controller side, it remains to be seen how this works out on devices and compatibility (and price of course).

When I first got my Philips Hue System I have been impressed and loved it from day one and do so till today. But we have not installed it in every room. And controlling it with your phone is great, but it’s also tedious to pick up your phone to turn on light in a room you are just entering and turning it of when leaving the room. We often end up using the light switches on the wall, which kills that whole Home Automation thing as lights switched off on the wall cannot be turned on again wirelessly.

IFTTT  and Philips Hue: just magic

Things got really interesting when I tested What a great service. With “If This Then That” it’s possible to interconnect different web services and trigger actions based on data or triggers of other services. I created a very small receipt turning on my Philips Hue lights at sundown and turns them off at 1 o’clock in the night as a fallback if I just forget to turn lights off when I go to bed.

And it really works well most of the time. And that is really magic. If you have Philips Hue installed. Give it a try. It’s magic. Yesterday I have cooked and thought that it’s about time to turn the lights on, a few seconds later they turned on. Without pressing a key. Without picking my phone. On cloudy days, you sometimes have to turn lights on before sundown, because it’s just kind of dark. This is where large scaled systems like IFTTT have not enough details.

That’s been the moment where I decided to make my own DIY cloud centered, iOS controlled, Arduino based wireless Home Automation System.


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Running Node.js on Arduino Yun

Arduino Yun is a great device once you learn how to use it correctly. Microcontrollers like the Atmel-ICs used in all nearly all Arduino compatible devices haven’t a lot of power or memory to Internet-Traffic. Of course they can, there are libraries and modules out there that will transform your little Arduino in a full-fledged Internet of Things device, but you will not have a lot of fun running it.

I.e. a typically RESTFul Web service will deliver so much JSON-Code that even a slightly more complex response will blow the memory of your Arduino.

Arduino Yun, and a few others like DigiX (sold in Germany for example by cboden) or Udoo solve this problem by merging the best of both worlds onto one device. Imaging a Raspberry Pi with an Arduino. If you want to know more about the difference between those two I have a small introduction on both devices.

Arduino Yun packs a full-fledged rather powerful Linux-machine onto an Arduino Leonardo. A so-called bridge allows the Linux part to talk to the sketch, and the sketch is allowed to run the Linux shell. This way you can use everything that has ever been build for Linux, the whole Internet-Stack, and the Arduino Sketch controls all that.

The previous example of running a rather complex RESTFul-Webservice, the sketch would run a Python, PHP, Node.js-Script on the Linux side that will request the data, process them, and delivers back only the really useful things to the micro controller. This way memory is now blown.

Since the latest software-update for Yun (see here on how to update your Yun) you are allowed to run Node.js on the Linux side of your Yun. That way you have a very powerful combination as Node.js is basically exactly build for that: Handling events in a very easy and transparent way. I have never really loved to work in Python, so I have been very pleased to know that I can write my Arduino Internet of Things Code in JavaScript using Node.js.


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Arduino vs Raspberry PI

It all started with Chumby One

Being a programmer my whole live, I have never really touched the hardware. I have developed all sorts of Applications, Platforms, web pages, etc. Being fascinated in small and mini computers I found myself buying a Chumby One a few years ago. This rather useless device (for me) launched my interest in small computers and programming them.

The Raspberry PI came into my home

A few month later I bought a Raspberry Pi (Model B) and started developing an interface for my ADF-Scanner. I loved the scanner, but I hated to mount it to my laptop and spending an evening scanning papers coming in the last months. I wanted a solution that runs the scanner and uploads the generated PDF-Documents to my Home Server (QNAP NAS) so I could scan a paper every evening without hooking up USB cables. As a simple user interface I ordered a simple LCD-Screen, hooking it up to the Raspberry PI. I got results, but I really did not like it and it was very unreliable. The Raspi lost WLAN connectivity, crashed or stopped. I think it has been powering issues perhaps now fixed in B+. But even besides that programming the Raspberry PI did not made me happy. Why? Because I had to use the Linux Shell, because all just felt like programming ordinary Computers without learning anything new but being restricted to odd C++ Frameworks, etc… And I did miss my Cocoa Frameworks. When developing rather large scale applications I really miss the clean, fast and reliable Cocoa-APIs  for Mac OS X or iOS Programming. I ended up implementing a small App on my rather old Mac Mini running fine till today.

Anyone else out there who is waiting for a small, cheap ARM-based Apple Device with GPIOs that can be programmed with Cocoa?

Arduino got my heart

A few months ago I discovered Arduino for me. I have heard of it a few times before. But I never really got behind the idea until I took the time to read a few articles about it. For anyone who does not know what Arduino is, I try to sum it up in a few sentences:

Arduino is a convention and a product. The Arduino products are small mini computers based around rather slow Atmel Microprocessors, ranging from 8 MHz around 70 MHz and memory measured in KB and not GB! But it’s also a convention in that everything around Arduino is Open Source and there are a lot of rules all Arduino devices follow – if a device follows there rules it is Arduino compatible and should run everything that has been developed for Arduino before by other groups or person that followed these rules. What makes Arduino even more great is that every schematic is open, so you can build your own Arduino compatible device from scratch if you follow the basic principles defined by Arduino.


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