Posts Tagged “Atmel”

The rubber hits the road. Sort of.

Now that the hull is (almost) complete, it's time to start soldering the electronics into place.
Now that the hull is (almost) complete, it's time to start soldering the electronics into place.

Due to other, exciting distractions (which I will mention in a later post), I haven’t had a chance to keep the blog up to date. Still, work progresses on the boat, and that’s the important part. Last month, with the keel now in its new position about 30mm further back along the hull, and sealed into place, it was time to add the electronics board.

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The Marvel of 3D Printing...

The prototype wind direction indicator.
The prototype wind direction indicator. The shaft is (deliberately) too long, and you can see the pair of low torque potentiometers at the bottom of the shaft. The housing was made using a 3D printer. Unfortunately, the PLA material is quite reflective, so it doesn't show up particularly well in this image.

So, while debating the different merits (or otherwise) of various mounting solutions, someone suggested using a 3D printer to actually print the housing for the masthead wind direction indicator. The more I thought about that plan, the better I liked it. As it happens, 091 Labs in Galway have a working 3D printer, from the Mendel90 family. What’s more, they are trying to get a 3D printing service off the ground! I wasn’t customer number one, but I was probably pretty close.

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I love it when a Plan comes together...

The ALIX 3D2 board under power, talking to a FreeBSD development system.
The ALIX 3D2 board under power, talking to a FreeBSD development system.

The new ALIX board has arrived. It’s to the left of the picture, sitting on top of a copy of the infamous Lyon’s Notes (which is appropriate). Also, the initial Atmel board with USBtiny programmer cable, serial cable to same development system, and a couple of WRAP boards thrown in for good measure.

It’s running my custom version of NanoBSD quite nicely, and can see the GPS without any difficulty. The GPS unit is a BU-353 unit (the USB version) which is out of the shot. It’s attached to the window, and gazing at the man-made stars. To give a breakdown of what’s in that photograph, the ALIX is on the left. In the USB port is the GPS, the RS-232 cable at the top of the board is communicating with my development machine (running FreeBSD). The red CAT5 cable is connecting the board to the “house network.” The Atheros CM9 radio is a miniPCI card mounted on the underside of the board. It works on 5.8GHz and on 2.4GHz. In this case, I’m using 5.8GHz because (apparently) it has better cross-water characteristics and the band isn’t as crowded. The mini coax cable is at the top-left of the picture, connected to a short, 9dBi antenna. You can also see a 12v cable with barrel plug. At the top-right of the picture is a WRAP board, also developed by PC Engines. It was being used as a testbed for the operating system, but that is no longer needed thanks to the ALIX.

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The Software...

The FreeBSD Daemon, ready to take on Neptune and his cohorts.
The FreeBSD Daemon, ready to take on Neptune and his cohorts.

I’ve been asked recently, about the software platforms used on board Beoga Beag. This seems as good a time as any, to talk about the various layers. As mentioned previously, the lower layer is a custom board, running an ATmega8 Atmel processor. The software (Igor and Otto) is custom-written in C for the boat.

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Battery and Solar Design

Sealed Lead-Acid Battery
Sealed Lead-Acid Battery.

Looking at the system power design, the majority of the circuits will run off a +5 volt rail. Those elements which need a different voltage, such as the main processor board, will derive their own requirements from the main Vcc rail.

There will be at least two Vcc busses on board. Labeled, oddly enough, as Vcc1 and Vcc2. The difference between them is that Vcc1 is always on, at all times, and Vcc2 (through VccN) are selectable by Igor.

The main processor runs off Vcc2, but Igor (and Otto) both run off Vcc1. In situations where voltage levels are critical, Vcc2 will be switched off and the boat will continue on whatever course had previously been set, until either voltage levels are healthy, the specified “wake-up” time has elapsed, or there are critical issues which require Mother to get involved. A critical situation could be something like a dramatic wind shift, or an error such as a mis-reading from a sensor.

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Igor and Otto

A custom-designed PCB from Kalopa Research, with an Atmel ATmega8 processor and a range of hardware options.
A custom-designed PCB from Kalopa Research, with an Atmel ATmega8 processor and a range of hardware options. This example is configured with an RS-232 port (the RJ45 socket on the left), 8 RC servo outputs, and a powerful "H-Bridge" motor controller.

The Kalopa motor control board was designed as a general-purpose Atmel board with ancillary electronics for a wide variety of purposes. It includes two H-Bridge motor controllers, driven by two 16 bit PWM outputs. You can exchange one of the motor controllers for an 8-channel servo controller, also using one of the PWM outputs. It has a standard RS232 port with an RJ45 connector on the end. There is a MAX232 to convert logic levels to proper RS232 voltages. If you want to use radio control, you can instead populate the board with an R5-434 radio receiver. It will listen for data on 434MHz and feed it to the Atmel. The processor itself is the bog-standard Atmel ATmega8 with 8k of code and about 512 bytes of RAM.

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The Main Systems Design

In terms of the system architecture, we’re planning on using two separate computer control planes to manage and steer the boat from start to finish.

At the lowest level, a custom Atmel (ATmega8) board will act as a basic “autohelm”, driving the boat to a specific True Wind Angle or TWA. As the breeze shifts, so too will the boat, to maintain that TWA. This is a basic PID algorithm for controlling the rudder and mainsail in relation to the specified TWA and is very similar in design and implementation to your average sailboat autohelm. This is the control board, also known as Otto or Otto von Helm, to give him his full title. Otto will most likely be assisted by Igor, in charge of power management and the boat environment. It is Igor who will turn on and off the other systems on board, including the main system (Mother).

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