Laptop interface to TackTick NMEA

Discussion in 'OnBoard Electronics & Controls' started by tspeer, Mar 4, 2008.

  1. tspeer
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    tspeer Senior Member

    I want to interface a MacBook to a TackTick NMEA interface to serve as a data logger and possibly a moving map display. Here is TackTick's diagram of the pinout of their interface unit:
    [​IMG]

    So how do I wire things up? Would a CAN Bus to USB converter be the way to go or an RS422 to USB converter? CAN-Ethernet gateway? Which pins to the connections shown?

    Anybody know of Mac software that will access the NMEA messages from USB port or Ethernet?
     
  2. Tim B
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    Tim B Senior Member

    Tom, Have a look at this pdf file...

    http://domain1154562.sites.fasthosts.com/products/userguides/NMEA Interface_pc.pdf

    this is pretty standard for NMEA 0813. Now, once you've got a normal serial port, you may need a USB to serial converter. This will give you access to a serial port in MacOS.

    Have a look at OpenPilot for ways to read this serial port and parse the NMEA data. At present OpenPilot only runs in Linux, but it shouldn't be too difficult to port to a Mac.

    Web-browsable CVS is here: http://openpilot.cvs.sourceforge.net/openpilot/
    the SerialIO section may be of particular interest.

    See the main web-page (below) for ways to download the source.

    Cheers,

    Tim B.
     
  3. tspeer
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    tspeer Senior Member

    Thanks.

    Not long after I posted my question, I found a much more straightforward solution. I'm going with a NMEA multiplexer. They typically take in several NMEA inputs, and have a computer-compatible serial output. For example, one model has 3 NMEA inputs and a USB connection, and it's powered by the USB. However, I've decided to go with the Shipmodul Miniplex-41BT.

    So I'll actually have a hardwired NMEA bus - all of about 6" long - with the TackTick NMEA interface as the talker and the multiplexer as a server or hub. This multiplexer has Bluetooth capability, so I won't even need to physically hook up the computer. I can also use a PDA as a cockpit alternative in the future. Its NMEA output supports interfacing to an autopilot, which is probably my next big-ticket item.
     
  4. tspeer
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    tspeer Senior Member

    System Architecture

    FYI, here's the digital system architecture that results.
     

    Attached Files:

  5. Tim B
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    Tim B Senior Member

    Cool. presumably the bluetooth link presents a "virtual" serial port. OpenPilot can handle this too :)

    Cheers,

    Tim B.
     
  6. tspeer
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    tspeer Senior Member

    Yes, it does.

    I'm actually leaning more toward TacticTool. It appears to do everything I need. Although I'm using a MacBook, I'm willing to use either an OS X or Windows application. Although I've done a lot of programming in the past, I'd much rather spend my time getting on with engineering the changes I want to make to the boat, rather than making tools to do it.
     
  7. yipster
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    yipster designer

    thats a very interesting bleutooth Shipmodul Miniplex-41BT Tom
    was thinking of answering but as now, no time, have some flowcharts tho
    had NMEA going over el girocompas, nav soft, GMDSS, atopilot and what
    half is ripped but like to get back that back in working order again
     
  8. tspeer
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    tspeer Senior Member

    I installed the multiplexer last weekend, and had it talking to the laptop in short order. Very straightforward.

    Now if only I could get the #$%^ TackTick GPS antenna working, I'd be set!
     
  9. RHough
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    RHough Retro Dude

    Do you have any idea what rate the TackTick network transfers data?

    I have to assume that the TackTick NMEA interface provides a NMEA 183 4800 baud data stream. You should be able to run that into a RS232 serial input (or serial/USB device). I don't see the need for the multiplexer (except for the bluetooth).

    FWIW, SeaLevel Systems has a very good serial/USB device. Some of the serial/USB gadgets don't provide a true RS232 serial port and refuse to work with some software.

    Are you planning to provide autopilot input from the laptop or do you just need the NMEA data in to the laptop for logging?

    If you are not going to use the laptop as a chartplotter to drive the autopilot, why does the autopilot need to be in the system? What NMEA sentences does it need?

    From your system drawing it looks like you have NMEA going into the Mux and two NMEA outs (one to the lap top and one to the autopilot). The Mux should have only one NMEA out channel. If you want to send laptop data to the AP, go from the laptop to the AP, not from the laptop to the Mux to the AP.

    It is asking for trouble if you try to use one of the Mux NMEA inputs for data output from the laptop. You must be able to configure the laptop output so it does not duplicate any of the information already in NMEA format from the TackTick system. That really confuses Mux devices.

    Have fun getting it all to work. ;)
     
  10. tspeer
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    tspeer Senior Member

    I'll know if I ever get the GPS talking! I think it's around 1 hz.
    At the time, I couldn't find just how to connect the NMEA to an RS232 connector. The multiplexer has RS232 output, which was one option with an RS232 to USB converter, but the Bluetooth option is really what attracted me. I've since found out how to wire directly between the RS232 and NMEA, but I'm glad I have the Bluetooth.
    Eventually, yes. An autopilot is next on my list of big-ticket items.
    I do plan to use the laptop as a chartplotter. With Bluetooth, I can also use a PDA in the cockpit as a repeater.

    I'm not sure, just yet about what sentences the autopilot needs. I should find out from the autopilot documentation when I buy one. I would expect the autopilot to receive APA or APB, maybe BOD, BWC, BWR, or BWW.

    I think there's a good chance these sentences will actually come from the GPS. It may be possible to download waypoints from the laptop to the TackTick GPS, otherwise I'll have to fat-finger them in through the Dual Digital display.
    The Bluetooth is bidirectional, so there's no NMEA between the laptop and anything. I've already used it to send setup commands to the multiplexer and receive data, so I've verified the bidirectional traffic. Right now, I'm only using the NMEA input from the TactTick system and Bluetooth on the multiplexer. I don't currently plan to add an NMEA Out from the multiplexer to the NMEA In on the TackTick system.
    Laptop to AP might be an option, but that would require a wire between laptop and AP. I'd rather use the multiplexer output or the TackTick NMEA output and keep the laptop purely wireless. I'm pretty sure the multiplexer can be configured to only output the sentences the AP needs. But even if it can't, the multiplexer NMEA out will send all the data to the AP. It would be useful to have high-rate heading data sent to the AP, but I'm not sure TackTick's compass supports that.

    The other reason to go from the multiplexer to the AP is because then I can use the autopilot without the laptop. The multiplexer will switch automatically from being a server if the laptop is present, to being a hub with no laptop.
    Absolutely. The laptop would have to only transmit new sentences that are not already in the system. It really comes down to which box is to be the one that combines everything into one stream - the multiplexer or the TackTick NMEA. I think the multiplexer is the more suitable node.
     
  11. RHough
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    RHough Retro Dude

    In one of my set-ups I ended up using an A/B switch to allow the AP to use the AP commands from the GPS unit when the laptop was not on-line. When the laptop was in use, the GPS data had to got to the laptop and the AP commands came from the chartplotting software.

    When using a Mux for NMEA to RS232, one problem I had was that the GPS put so many sentences out that when there were 3-4 NMEA 'talkers' going into the Mux the single 4800 baud output could not handle all the information. The Brookhouse Mux allows a 9600 baud RS232 output to keep up with the data from multiple inputs, but at least two of the navprograms I've used cannot be configured to read NMEA sentences at greater than 4800 baud so the feature was useless.

    If the TackTick system GPS puts the AP sentences into the network and waypoints can be input from a TackTick control head, you may have a problem with duplicate information from the laptop. I don't know of any GPS receiver that allows the user to select the data output or to turn off sentences you don't need/want.

    Another thing to consider is how much laptops like sailboats ... I have 3-4 dead laptops ... one bit of spray into the companionway and the magic smoke leaks out ... :( Laptops are also power hogs, 70W is almost 6A @ 12VDC. A chartplotter like a Raymarine E80 draws less than 2A and is waterproof.

    This is on your Tri? Are you running a wind instrument on a rotating mast? How does TackTic handle the mast rotation correction so you can get True wind and VMG information?

    I'd like to learn more about the TackTic system and your success or lack thereof in interfacing with non-TackTic devices. I get asked about their stuff all the time and only have limited experience with the line.
     
  12. tspeer
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    tspeer Senior Member

    I'm hoping to use the multiplexer as a software-controlled A/B switch, in the way that it switches between server and hub modes.
    The NMEA in is 4800 baud, and the multiplexer's NMEA out #1 can handle 4800 to 38,400 baud. The Bluetooth is 38,400 baud and down, depending on what the laptop wants. The second NMEA out is only 4800 baud.

    The multiplexer can handle one 4800 baud input with no problem. Multiple 4800 baud inputs can lead to buffer overflow if using a 4800 baud output. However, in server mode, sending the output to 38,400 baud outputs (Bluetooth and NMEA Out #1 only) will empty the buffers fast enough to avoid overflow.

    As a controls guy, I'd love to have lots of high-rate feedback of heading, angular rates, and accelerations to the autopilot, but that's not what this system is all about!

    I'm really only speculating right now. I don't know what the GPS outputs or what the AP needs. I need to get it going as a data logger first, then I'll add the AP as a standalone unit, and finally integrate it into the system.
    Yes, that's a problem, and why I don't want the laptop to be near the companionway. It can be well inside the cabin, thanks to the wireless interface.
    I need to do a power budget for the system. Thankfully, much of the TackTick system is self-powered. For what I'm doing right now charting is not a high-priority function, as I can navigate visually for everyplace I'll be going in the next couple of years. Data logging is my #1 priority. But even there, I could leave the laptop off until I'm on condition and ready to start testing for real.
    It is on the tri, but I have a fixed mast. A big point of the whole exercise is to build a VPP as a basis for engineering future changes to the boat. Like a new rig with a rotating mast. Since that would cost probably half as much or more as the whole boat cost, I've a powerful motivation to get it right the first time. When you're experimenting at full scale, some effort at risk reduction can save a lot of money and time.
    TackTick makes a mast rotation sensor. I suspect it's another flux-gate compass that gives them mast rotation via the differential from the hull compass. I'm not sure how accurate that all is. I could easily see it have 1- 2 deg RMS error.
    The owner of the boatyard where I assembled the tri (and a trimaran owner himself) said, "TackTick is probably the most bang for the buck," and I'm inclined to agree. So far, except for the GPS, I've been very satisfied. The system has been easy to install and worked as advertised. Except for the GPS. So far.

    FYI, here's what one frame of NMEA data looks like from the TackTick system with just the sailing instruments:
    $IIHDG,309,,,,*5D Heading, 309 deg magnetic
    $IIMTW,+08.0,C*30 Mean water temperature, 8 deg C
    $IIMWV,251,R,13.4,N,A*13 Wind speed and angle, 13.4 kt @ 251 deg Relative
    $IIMWV,253,T,14.2,N,A*16 Apparent wind speed, 14.2 kt @ 253 deg True
    $IIVHW,,,309,M,00.0,N,,*6E Water speed & heading, 0.0 kt @ 309 deg magnetic
    $IIVLW,00062,N,000.0,N*57 Distance traveled through water, 62 nmi total, 0.0 nmi trip
    $IIVWR,110,L,13.5,N,,,,*78 Relative wind speed & angle, 13.5 kt @ 110 deg left of bow
    $IIDPT,007.0,-1.0,*47 Depth of water, 7.0 meters, 1 meter transducer to keel
     
  13. Tim B
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    Tim B Senior Member

    Tom,

    You sound like you're getting close to the advanced features we'd like to see in Open-Pilot. Ooops, there I go, plugging free software again!

    Anyway, on a more serious note, have you done any serial programming on macs? If so, could you pass me a read routine and I'll try to get something into the OpenPilot NMEA library so that you can use at least the basic NMEA test app. Please note that I don't have a mac, but I can e-mail you the code off-list if you like.

    From the data you've put at the end of the last post I can certainly add some functionality to the NMEA parser to handle those sentences.

    If you want, I can e-mail you the windows test app. I don't know how well the com ports are emulated.
     
  14. Tim B
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    Tim B Senior Member

    I've incorporated the tactic sentences (though I have no way of checking them).

    Tom, would you like to run the attached code with an appropriate COM port?

    Source is available at http://openpilot.cvs.sourceforge.net/openpilot/

    Cheers All,

    Tim B.
     

    Attached Files:


  15. yipster
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    yipster designer

    dug up the 10 year old selfmade flowcharts and see tacktick is a dutch product
    but i'm having a hard time re-understanding my own drawings so i'll save you for now
    yes there is a seatalk/nmea box i forgot behind the dash and a fluxgate compas
    external antenne to gps worked first time but recall nmea out from gps did not
    only found out after using a phony signal (but floppy is gonne) as i think Tim mentions
    i like that bleutooth, sorry i'm not of help but get it working, its impressive stuff
     
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