I had to work a little bit on an audio solution to get sound samples using a micro-controler. I based my design on an Internet really known circuit but I had to optimize it a little bit to be more efficient in terms of energy. This post is giving the result of my hack.
Gimp header file format
For sure not a lot of people is using “save as .h” capability in TheGimp. But this is a really easy to use solution when you want to embed some icons or image into a C/C++ source code. I used this functionality with Arduino to display graphical elements and I was convinced of it.
I also reused this format to transfer an image over Bluetooth as this format have the advantage to encode RGB values into printable characters. The format is not too much expensive as 3x8bits RGB values are encoded with 4 chars.
This post gives detail on this encoding and a procedure example to encode your bitmap into this format. The decoding procedure is given by TheGimp in the .h file itself.
I recently had to design a solution to power a arm based system like arduino with an external power supply but, as this system have to stay up even if current is cut, I also had to backup it with a battery. This post is describing the design for a such circuit.
I already wrote some stuff about Sigfox here, so may know that it is a really promising French technology IoT oriented. So I have a project to connect a Raspberry Pi and arduino system on a such peripheral. The use of this technology is quite easy as it works like a modem, based on AT command transfered over a 9600bps serial line. The main issue is that the chip is really CMS and hard to hack at home easily… by the way, as you see, a poor soldering makes it working for the test purpose.
As much as I have test, I can say that using this device to communicate with an Arduino or a PI is really easy ! code can be written in less than a minute ; compared to what you have to do to make wifi / Ethernet / GSM working in a stable way, this is incredibly easier ! You can also use the device as an autonomous sensor for temperature and contact switch of your choice for an affordable price. In my point of view one thing is missing : you do not really know the signal quality and if you have a good connection or not with sigfox network. [update] The RSSI is indicated in the SigFox Api on the backend side for each of the received messages [/update] . Meaning you must receive the first one to know if the location is covered or not. This can be a problem to deliver a product and get an easy support to your consumer. The other limit of the technology, as much as I know is that you can transmit data but not receive some from the SigFox network [update] The ability for the device to receive messages will be soon added with limitation, but it will [/update]. In many case it is enough but sometime you like to respond to a specific value received. Read next to get details on how to use it …
Last year in December, I gave a talk on Internet of Things, here is the youtube video (in French) – The slide are also here : http://slid.es/disk91/internetofthings
Yesterday, I was in Grenoble for the Eclipse IoT days. It was a great opportunity to listen and learn from some actors of the IoT movement. The day was on the campus where we have been invited to see some student work on home automation and robotic for telepresence (see my twitter photo feed). The day was intensive on conferences with the really good quality and interest.
Most of the discussions / demonstrations were based on Home Automation, Smart house and globally telemetry. Not many industrial applications has been shown but some of the companies are working on industrial domain. Most of what has been shown is applicable on industry.
All the project are separating sensors, based on low cost / low energy devices associated to a local management/administration platform connected to Internet. The technology in use are mostly :
– RF and ZigBee for sensor to management platform
– Java for the management platform running the OSGi platform (Java) (this is also due to the fact Eclipse were organizing the conference and OSGi is Eclipse framework) This OSGi framework integrates management tools to connect / upgrade the platform remotely.
– Mqtt to communicate on Internet
– A custom MDM solution is deployed to manage the platforms (generally based on server management solution instead of MDM solutions) like roboconf.
Regarding the different architectures, some maintain the data on site with a in-house user interface, some export data outside on “cloud” with an on-Internet user interface. As much as I’ve seen the in-house strategy is largely loosing on performance and interface quality due to the limited power of the management platform to perform advanced HTML experience. I assume this is also related to the Java choice to run these applications.
The other interesting learning is that most of the companies are using Raspberry Pi and Arduino to prototype solutions before, I assume, building a more robust platforms. Opensource is also mainly used and presented as the only solution to make the IoT market based on standard to be integrated all-together.
I had to control power on an external circuit using an Arduino. the objective was to delay the power-on of a device consuming about 3A. One of the solution is to use a relay but it is a quite expensive solution another one is to use a Mosfet. This is the solution I’ll describe here.
For one of my projects, I want to have a really low power consumption device to be able to use a battery for many month. For this I implemented a low power solution as described here. I’ll try to simplify it a little bit and document it a little more …