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Discussion Starter · #21 ·
I've built some simple things out of Arduino. Looks like from a brief search the Raspberry Pi system doesn't have an on board A/D converter, but people have built them and there maybe some kits.

If you have analog sensors for things like oil pressure, I don't see why you couldn't design a high impedance interface that would just go in parallel across the sensor with whatever gauge you got to measure a voltage level without impacting the gauge. Then you could infer a resistance level and translate in code to an oil pressure for example.

I've never really dug into the NEMA stuff, so no help there.

Warning, every time I start messing with some hack like this, it's more work than originally planned:) Best of luck.
You're right about more work than planned.

Your idea is intriguing. I'm concerned about "inferring" resistance levels though. I mean, where do I correlate the values to to determine true pressure without "teeing" in an analog gauage?
 

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Can the pie run open cpn? I have an Intel atom processor machine that runs on.12 volts that I plan to run open cpn on.

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Discussion Starter · #23 · (Edited)
Can the pie run open cpn? I have an Intel atom processor machine that runs on.12 volts that I plan to run open cpn on.

Sent from my ADR6425LVW using Tapatalk
Pi is ARM chipset. I believe it *CAN* run OpenCPN, but you're going to have to modify it and recompile it. Even if it does run it, it'll be poor performance since the Pi is only a 700mhz chip (not really apples to apples to compare ARM w/x86). In fact, apparently, here is a youtube video
and here is how to make it happen http://www.agurney.com/raspberry-pi/pi-chart

[strike]In my opinion, the Pi really isn't the right board for an ACTIVELY used boat computer. Its better as a lightweight, low power back-end server type device. [/strike]

[EDIT] I stand corrected! Per http://www.mouser.com/applications/open-source-hardware-galileo-pi/ the better board for media type "stuff" is the Pi vs the Galileo...which is based on NUC. THat being said, Intel NUC systems I've seen online are 1.8Ghz...so serious power.

If I were to be making an actively used front end boat computer, I think I'd use the INtel based chipset (non-arm). x86 so much more software available in packages already. Though, I think they consume around 27Watts full/6 watts idel which is much more than a Pi.
 

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Almost all engines are either fitted with analog temp and oil pressure gauges , or have the fitments to easily add them, this includes adding turbo and gearbox oil pressure.

There is no need to have sperate senders for the electronics, you will need to buffer the existing analog senders with a high impedance instrumentation op-amp to avoid affecting the existing gauges. No big deal if you know what you are doing.

as to Pi or NUC, little real difference, You'll be running linux on both almost certainly, it boil down to preference.
 

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I've built some simple things out of Arduino. Looks like from a brief search the Raspberry Pi system doesn't have an on board A/D converter, but people have built them and there maybe some kits.

If you have analog sensors for things like oil pressure, I don't see why you couldn't design a high impedance interface that would just go in parallel across the sensor with whatever gauge you got to measure a voltage level without impacting the gauge. Then you could infer a resistance level and translate in code to an oil pressure for example.

I've never really dug into the NEMA stuff, so no help there.

Warning, every time I start messing with some hack like this, it's more work than originally planned:) Best of luck.
Consider using the Beaglebone Black. Its got an on-board ADC. Generally better equipped for interfacing to real world versus the Pi.

Still not sure what you are trying to accomplish here. Conversion of several analog signals to an NMEA 0183 data stream? Or conversion of several analog signals to an NMEA 2000 data stream?
 

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Discussion Starter · #26 ·
Consider using the Beaglebone Black. Its got an on-board ADC. Generally better equipped for interfacing to real world versus the Pi.

Still not sure what you are trying to accomplish here. Conversion of several analog signals to an NMEA 0183 data stream? Or conversion of several analog signals to an NMEA 2000 data stream?
NMEA 0183 data stream...for now!
 

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To the OP -
Am considering this same project to write NMEA 2k sentences to garmin 740 at the helm - ancient Volvo MD7A and new gauges (analog) - I designed the panel to stub out for this eventual project, so I have the data readily available for collecting - interested to know which Arduino board you chose and why as well as any sketches you can share - PM me if you can...

Thanks
Eric
 

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Have you taken a look at the Freeboard project?

Its designed around RasPi and has multiplexing for NMEA. If you dont want the charting and instrument interface you can at least poke around the source to see whats libararies are being used for NMEA input.
 

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I prefer the Raspberry Pi.. It has a complete Unix type os with at least three different C-compilers. Windows os.. Connect to HDMI and Wireless keyboard/mouse (to reduce power from pi).. Then develop any software you want. Ethernet to router for complete access to web or...

There are numerous A/D implementations for Pi. They connect I2C or SPI.. 16 bit A/Ds much better that the Ardino 8 bit A/D.

I use a PI as a usb to Ethernet bridge to connect my router to a Mifi so my computers, tablets and phones are always connected..
Bryce
 

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Once we get into the price of a Cubietruck a whole range of options open up.. Such a Gigabyte GA-J1900..

Amazon.com: Gigabyte Built-In Intel Celeron J1900 (2.0 GHz) Dual LAN Mini ITX DDR3 1333 NA Motherboard GA-J1900N-D3V: Computers & [email protected]@[email protected]@http://ecx.images-amazon.com/images/I/61Ho%[email protected]@[email protected]@61Ho%2Bh3VzyL

This gives us a dual core 2 Gigahertz X-86 CPU that can run Linux or windows.. Add dram.. Still about same price as a Cubietruck..
 

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How/where is the NMEA 2K decoding being done? OpenCPN able to decode 2K? 2K first converted to 0183 by? etc. Thanks.
OpenCPN able to decode 2K ? - Not yet

Check out canboat which has reversed engineered much of the NMEA 2000 protocol and Signal K which may ultimately integrate the canboat work and convert NMEA2000 into JSON and implement an interface to openCPN.

Otherwise you are looking at a NMEA2000 to NMEA183 blackbox to openCPN.

Marc
Crazy Fish - Maintaining, Upgrading and Sailing a Crealock 37 | SV Crazy Fish
 

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· Bill SV Rangatira
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would be nice if it had more than 2 serial ports for nmea 0183
That is an excellent point.. If I was going to use this board.. I would probably use a usb to rs232... $20 per port.. I don't see this as a solution on my boat.

The way I see it.. Nema2000 is not the future of sailboat networking.. Giga-baud Ethernet along with dual band AC is the future. The instrument manufacturers are now coming around to that..

The way I see it .. For now.. Distributed PIs placed at the instruments can provide the Ethernet bridge.. Very Cheap.. Low power.. Easy to manage..

The thought of a plethora of different networks rambling about the boat seems clumsy.. And the price of Nema 2000 cables, connectors and adapters is crazy. And you only get 500k baud.. Really!!
 
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