26 Jul 10 Ethernet over mains power lines

I’ve been using a really clever device for the last few years that a lot of people seem to be unaware exists. It’s an ethernet over powerlines adapter – one such example is the Devolo dLAN. In a nutshell, you plug it into the mains, and connect the Ethernet socket to your network device. You can then plug as many others as you like to various other powerpoints and extend your network wherever the power stretches. Devolo do ones that run up to 200mbit. It’s a theoretical maximum, although I’ve got 177mbit before which is impressive. It has a couple of downsides:

1. It won’t traverse 3 phase power. I’ve tried it, and I’ve ended up with a very weak/nonexistant signal which is probably more inductance than anything else.
2. Obviously it doesn’t handle bad cables well – it doesn’t much like extension cables either.
3. Different circuits work about as well as 3 phase power, the only signal you will get is probably inductance between the two circuits.

Some advantages:
1. It travels pretty far. I’ve had over 150mbit between adapters at opposite ends of the house.
2. No new cabling
3. Fully supports standard Ethernet so all network protocols will work just fine over it.
4. I love it

For anyone running a home or office network and not fortunate to have Ethernet points cabled in, I strongly recommend these devices, you’ll never know the difference.

Tags: devolo, ethernet, LAN, network

31 Jan 10 Linux Controlled Door Entry

Having recently moved to a new apartment, one of the first things that I decided to do was build an RC entry system

Here’s some pictures:

The black box at the top is a simple Velleman RC control kit and the black box below is a 240VAC->12VDC regulated converter.  The Velleman RC receiver has two relays, one connected to an electric strike lock and the other connected over the button input in the entryphone which unlocks the main door.

On the RC transmitter there are two buttons, and as they are currently connected, one opens the main door and one unlocks the electric strike on the apartment door, with a 5 second timer on each.

This works well so far and I have paired the transmitters with the receiver so that default unpaired transmitters will not activate the relays. A few weeks on, having already locked myself out once, the next step is to extend this project.

I intend to have the RC transmitter connected separately to some embedded linux board, probably the spare Alix and Phidgets boards I have from the robot I built a while ago. The linux board will signal over a separate frequency to this door entry system. The linux board will perform a variety of functions from logging entries to automated surveillance.  Additionally the linux board will have net access and possibly run asterisk. I can either SMS my way in or alternatively call in to asterisk and do some voice authentication. More to follow when I actually have time to get this done..

Tags: alix, asterisk, embedded linux, phidgets, rc transmitter, sms, velleman

15 Jan 10 Embedded Linux Programmer

As an embedded linux programmer, I’ve had the opportunity to work on a number of different platforms, MIPS being one of my favorites.

There are a few general limitations that you’ll find. You have limited CPU power available, you have very little RAM available, and for more advanced operations and optimizations, your CPU will generally have a limited function set.

The usual good programming practices apply, but are of much greater importance. Specifically, don’t allocate memory that you don’t need, and dont put the CPU under undue stress with unnecessary or badly optimized loops. Taking C syntax and some pseudo code;
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Tags: assembler, embedded, loop, mips, optimize, x86

19 Sep 09 Installing Linux on the Embedded PPC50 Touchscreen

I personally really like this touch screen PC! I’ve installed Debian (of course), graphical interface, and configured the HUAWEI data card along with the TSCOM touchscreen drivers.

I also modified the boot up to log in and start the graphical interface automatically. Using xvkbd for a virtual keyboard works really well, and I might just have to carry this around in the car along with the datacard for those emergency situations.

It’s a simple x86 with 1GB diskspace and 1GB RAM. The device takes a simple 12V/6A input and therefore wiring it up to a car, battery, or other portable power supply shouldn’t be a problem!

Any ideas what next?

Tags: datacard, debian, embedded, Huawei, Linux, ppc50, touchscreen, tscom, x86, xvkbd

05 Aug 09 Using the Phidget Interface Kit under Linux

Further to a comment I received http://www.adamsinfo.com/the-robot-phidgets-usb-interface-board-kit-works/comment-page-1/#comment-490 I thought that it might be a good idea to write a quick high level overview of getting the USB Phidget Interface Kit working under Linux. In my case I am of course using 32bit Debian, however these instructions should mostly be portable to any other Linux based OS

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Tags: debian, gcc, Linux, phidget, phidget interface kit, usb

28 Feb 09 Linux and the Huawei HSDPA 3G E220 modem for mobile broadband

Installing the Huawei E220 modem under Linux is so so easy. Probably easier than running through the Windows XP Setup tool actually!

Prerequisites:

1. Kernel version equal to or greater than 2.6.20 (There are workarounds availble for older kernels)
2. wvdial (You can use any serial dialer I guess)
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Tags: 3G, E220, HSDPA, Huawei, Linux, mobile broadband, UTMS, WCDMA, wvdial

26 Nov 08 The Robot: Hardware working and ready to go, a few minor glitches

Progress has as always been good lately. The robot boots up quickly and appears on the wireless LAN, with openssh running. The internal Atheros miniPCI wasn’t doing the trick and wireless performance was shaky at best. I’m using an Alfa Networks USB adapter (r8187) and an 8dBi gain antenna now, so this has some distance now!

I was also getting frustrated with the laggyness of the board while VLC was running for streaming audio and video and so I decided on an IP Camera (Edimax), which is connected directly to the LAN port on the Alix board (I don’t have any reason to use it for anything else).

The motor control script works well and the device is responsive. At this point I can drive the device around

relatively easily and accurately, stream video and audio back to my laptop, which again is connected wirelessly.

Using ‘espeak’ you can easily generate a synthesized voice to provide easy text to voice:

Everything is working great and I’m pleased so far. The only reason why there isn’t a video up yet is because I haven’t had the time! There will be one up shortly.
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Tags: 8dbi, alfa networks, alix, antnna, atheros, cf card, distance sensor, edimax, espeak, gain, hardware sensors, ip camera, Linux, motor control, phidgets, picolcd, power consumption, r8187, SD card, serial, usb, usb to ttl, vlc

20 Nov 08 Linux: AVIT Research USB to TTL Cable

I ordered a USB to TTL Cable to control two Sabertooth 2×25 motor controllers as part of the Robot project.

I plugged it into a Windows PC, and used ‘RoboRealm’ to control the motors via the COM port that appeared. Worked perfectly. Motors, controller, USB to TTL and virtual COM port – excellent.

I then plug the cable into my Linux board and guess what, no driver claims it and I have every standard USB Serial module compiled. AVIT Research’s website also gives no help on Linux support.

The device shows up under lsusb as:
Bus 002 Device 002: ID 10c4:818b Cygnal Integrated Products, Inc.

The solution was luckily simple. After prising open the cable and doing some research, the ‘cp2101′ driver is the one that we want. I’m using 2.6.27.6 but this should work for any cp2101 version.

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Tags: 10c4:818b, 2.6.27.6, AVIT Research, com port, cp2101, cygnal integrated products, diff, Linux, Linux robot, lsusb, motor controllers, roborealm, Robot, sabertooth, usb to serial, usb to ttl, virtual com port

16 Nov 08 The Robot: Base, Wheels, Motors, and Sabertooth Motor Controllers

After attaching the 4 motors and brackets to the acrylic square, I found that it started to dip slightly due to the weight, and as I’d planned to put a 1.5kg lead acid battery in the center and I realised that this needed to be addressed. Rather than another visit to Homebase for some steel reinforcement, I just stuck (melted) two pieces firmly together with polycarbonate acid glue and then trimmed the edges with an electric saw.

Here is the base, the insulation tape all over the place is to hold down the connectors that I won’t be needing. The motors all contain encoders which I didn’t just want to rip out, so I’ve preserved the connectors for future usage, and just cut the – and + cables in a way that they can easily be reconnected to the connector if I ever want to. They were expensive motors so I didn’t want to ruin them!

If anyone is wondering why I didn’t attach standoff cylinders to the controller’s super large heat sink rather than attaching it directly to the acrylic base [which would normally be a bad idea], it’s because I didn’t have any standoff’s left, and the controllers are capable of 25A per channel. I will never drive them at higher than 4A, and the motors running on 4A for 30m or 2A for 2 hours solidly as a test didn’t generate any noticeable heat on the heat sink at all. At first I had also predicted the use of a fan to suck air in from the base, but I’m not sure it will be necessary, as nothing seems to get remotely hot so far..

I’ve also slightly indented the 4 points where the acrylic cylinders will be glued, just for extra stability. The motors are all wired to the two motor controllers, which has a junction box waiting for 12v now. The picoPSU should arrive some time this week, so hopefully I can get on with it.

The wheels are omnidirectional as they contain rollers. It’s a clever design and it seems to work well. Infact, I’m pleased with the way the motors and wheels ended up. Instead of having to work with two wheels and spending time on calculating angles for servo motors and turn radius, I can just attach 4 motors instead in the configuration that I have and using omnidirectional wheels. The motors will pull a lot of weight and I only have to concern myself with backward and forward for each motor, which in any combination will allow it to move in any direction. Hey, I’m not saying that I ‘invented’ this ingenious combination, just taking the credit for a smart move in implementing it! I have connected a power source directly across each of the motors to test. They are straight, and when I turn them all in the same direction, the board rotates around a ‘very almost perfect’ fixed axis which is great. I had in mind when I was positioning these, that I didn’t want to spend a ton of time in the software compensating for wheels that aren’t straight.
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Tags: 2x25A, analog voltage, battery, ground, lead acid, Linux, Linux robot, motor, motor controller, omnidirectional wheels, packetized serial, picopsu, rc input, sabertooth, simple serial, the robot, tx pins, usb to ttl

14 Nov 08 The Robot: A body, Sensors and Good Progress

Progress is going really well and I’m happy so far. Unfortunately I didn’t want to show the body yet as it is so far from finished but as I haven’t posted an update in a while I decided to just go with it.

The body is ever so slightly lop sided by a few mm here and there which is a shame however from a short distance you wouldn’t notice, it stands up straight and weight distribution is equal throughout the base plate so I’m happy with it. Ok, ‘professionally’ the body’s a mess however for my zero experience in that kind of work, I’m reasonably happy.

This is the front of it, top is a mounted webcam, to the left of that is a phidgets temperature sensor and top right is a phidgets light sensor. I am waiting to add 8 colored status LEDs around a small flat panel 5v stereo speaker as a ‘mouth’ (I got it from a Nokia phone bundle).
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Tags: battery pack, distance sensor, IR remotes, irda, LED, light sensor, Linux, Linux robot, MAX232, motor controller, nimh, phidget, phidgets sensor, picolcd, picopsu, polycarbonate glue, sabertooth, serial port, stereo speaker, temperature sensor, the robot, usb phidgets, usb sensor kit, webcam