Teensy – Arduino on Steroids

2014/11/062015/02/02 Phillip Schuster 2 Comments

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

2014/09/062014/09/06 Phillip Schuster 4 Comments

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 IFTTT.com. 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

2014/08/262014/08/27 Phillip Schuster 1 Comment

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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