YAPP: Homemade Seatalk to USB interface

AngusMcDoon

AngusMcDoon

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Yet Another Pointless Project...

OpenCPN can now show boat data on the side of its window if wanted, for example boatspeed and wind data. It calls the feature a dashboard and is shown here...

ocpn.jpg


The data is read by OpenCPN in NMEA format on a standard serial port. This is ok if you have all your boat data in NMEA format, and a serial port available. But if, like me, your boat data is in Seatalk format and your laptop does not have a serial port, then you need some extra stuff. You could pay Raymarauder a fortune for a Seatalk to NMEA converter, and then pipe this through a RS-232 to USB converter, but it's a bit of bother. Instead - here's the latest YAPP...

SDC11204.jpg


This YAPP uses a cheap PIC processor (£4.50 18F4550) that has USB capability. Attached to it is a small amount of electronics to make the Seatalk bus readable...

SDC11203.jpg


This is then converted in the software on the chip to NMEA data format (but not electrical format). The software then works like one of those RS-232 to USB converters. When plugged in to a PC a standard COM port appears, and OpenCPN can be pointed to read its NMEA data from this. In geekspeak, the circuit and software implement a USB class 2 CDC device. The device can be seen as a new port...

d3.jpg


A normal serial terminal can be used to see the raw data coming in...

nmea.jpg


The power for the circuit is taken from the Seatalk 12V line to minimize current draw from the PC's battery. In USB speak this is called self-powered, and the USB standard is quite strict about not supplying current to the USB power lines from a self-powered device. The circuit has to sense when it is connected to USB meet this requirement.

Once Seatalk data is read and parsed (same code as a previous YAPPs) it is simple to re-format it into NMEA and bung them out the USB. A small device .inf file needs to be created that is pointed to when first plugging the device in. Windows requests the driver in the normal way...

d1.jpg


Of course, on a small boat, this is all pretty pointless, as I only have to stick my head round the companionway to see the instrument displays anyway.

Total cost of bits was about £6. Sauce code and schematic to anyone who's interested, although it will be 2 weeks before I am back on dry land with a proper internet connection before I can send it.
 
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What a great project, I really would like to have a bash but our instruments are 20 year old B&G and goodness knows what language they speak! So for me it really would be a YAPP.

I see you have a Dragonfly 920, a fine sailing machine, my pal has one in Calpe and we have been known to do the Spanish Series Calpe/Formentera Race race, unfortunately they haven't been able to give us a handicap so far so we just go as associates. Suprisingly good in the rough stuff and wicked on a close reach, not much under 50ft beats us two old geezers:D
 
I'm not really sure about this (background originally in software) but would the iDwaRF board (http://www.chip45.com/AVR-2-4GHz-IS...-168-Wireless-Radio-Module-AVR-ATmega168.html) be suitable? The would solve the smd problem.

At 22 Euros it may, of course, be outwith your usual budget constraints.

Philip

ps: Elektor web site has a free article on these. Seem to offer quite interesting developments - sending and receiving info via com on pc and various sensors.
 
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Sorry about the lack of replies to the suggestions. I am away boating at the moment and mobile internet prices in the Isle of Man are beyond my budget, or willingness to pay anyway! I'll have a look when I get back.
 
dgadee said:
What abot a yapp project posting data to wifi. Isn't usb so last year?

Philip
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Why WiFi when you can do it with bluetooth, which is simpler and takes less power? The BT range is also more than sufficient even for a 50ft yacht.
 
AngusMcDoon said:
Yet Another Pointless Project...
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This is excellent. What about making it into a kit? Have you tried to contact Jaycar? I am not suggesting Maplin because they are useless. PBO would be ideal, but they are too busy publishing toilets refits and pointless teak accessories projects that fit 30 year old boats that hardly anybody own.
 
haydude said:
This is excellent. What about making it into a kit? Have you tried to contact Jaycar? I am not suggesting Maplin because they are useless. PBO would be ideal, but they are too busy publishing toilets refits and pointless teak accessories projects that fit 30 year old boats that hardly anybody own.
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I suspect that sellling anything with 'Seatalk' in the product description is inviting a snotty letter from Raymarine's lawyers. It's not an open standard. They either turn a blind eye to, or don't know about, people who play with it for their own interest and publish their results.
 
AngusMcDoon said:
I suspect that sellling anything with 'Seatalk' in the product description is inviting a snotty letter from Raymarine's lawyers. It's not an open standard.
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You would need to recognise the trademark "Seatalk" in any description of such a product but European law expressly permits the use of reverse-engineering for the purpose of making interoperable products.

This link states :
The unauthorised reproduction, translation, adaptation or transformation of the form of the code in which a copy of a computer program has been made available constitutes an infringement of the exclusive rights of the author. Nevertheless, circumstances may exist when such a reproduction of the code and translation of its form are indispensable to obtain the necessary information to achieve the interoperability of an independently created program with other programs. It has therefore to be considered that, in these limited circumstances only, performance of the acts of reproduction and translation by or on behalf of a person having a right to use a copy of the program is legitimate and compatible with fair practice and must therefore be deemed not to require the authorisation of the rights holder. An objective of this exception is to make it possible to connect all components of a computer system, including those of different manufacturers, so that they can work together. Such an exception to the author's exclusive rights may not be used in a way which prejudices the legitimate interests of the rightholder or which conflicts with a normal exploitation of the program.
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Boo2
 
Don't you think though, that despite the law above, Raymarine would still try the legal threat approach, probably using the last sentence of the paragraph you quoted? They would know that I couldn't defend myself legally against a large corporation. That's pretty much the way big companies work, isn't it? Especially ones with their backs against the wall, like Raymarine.
 
AngusMcDoon said:
Yet Another Pointless Project...

Total cost of bits was about £6. Sauce code and schedmatic to anyone who's interested, although it will be 2 weeks before I am back on dry land with a proper internet connection before I can send it.
Click to expand...

Yes, I'm interested, please send details when you can, thanks
 
AngusMcDoon said:
Don't you think though, that despite the law above, Raymarine would still try the legal threat approach, probably using the last sentence of the paragraph you quoted? They would know that I couldn't defend myself legally against a large corporation. That's pretty much the way big companies work, isn't it? Especially ones with their backs against the wall, like Raymarine.
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Yes, you are right to run from lawyers but the European system is supposed to encourage producing software which interacts with other software. Big case in London last year:

http://www.bailii.org/ew/cases/EWHC/Ch/2010/1829.html

which you might find interesting. No doubt the final costs were as gigantic as usual.
 
AngusMcDoon said:
Don't you think though, that despite the law above, Raymarine would still try the legal threat approach, probably using the last sentence of the paragraph you quoted? They would know that I couldn't defend myself legally against a large corporation. That's pretty much the way big companies work, isn't it? Especially ones with their backs against the wall, like Raymarine.
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Yes, it's definitely a risk. Personally, I think it is shameful the way big firms browbeat individuals into giving up their rights to free speech (pace the McDonalds duo in the McLibel trial). It's easy to understand how someone who was receiving little or no income from a project would rapidly come to the conclusion that the game wasn't worth the candle.

We're all very glad to see you standing up so nobly for our rights, Angus :D:D

Boo2
 
GAJ said:
...our instruments are 20 year old B&G and goodness knows what language they speak...
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The B&G network has not been reversed engineered as far as I know. Probably not enough around to make it worthwhile. I expect it is possible though with an oscilloscope and lots of time.

GAJ said:
I see you have a Dragonfly 920. Suprisingly good in the rough stuff...
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:eek:

You can't say things like that here! The lead miners will start shouting at you. I had a 69 mile beat up the Irish Sea against a F7 earlier in the week. I capsized 3 times and all my beam hinges broke at least twice. :D
 
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