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Thread: PICAXE handling GPS for robot boat

  1. #251
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    Quote Originally Posted by Robin Lovelock View Post
    Thaanks Folks. I think Jim ordered stuff like this, and - if he gets something working - he may post onto this thread.
    I have a couple of different boards which I will be testing over the next few weeks - also have a mechanical and electronic compass to check calibration with!
    Time is natures way of stopping everything going wrong at once

  2. #252
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    I can understand your problem Jeremy, and I too was worried that the autopilot might be "confused" by the tide. If you start with www.gpss.co.uk/autop.htm you can go from there to an earlier copy of that page (i.e. for 2012) and there you will find my worries - dispelled after that November launch. Despite ending up on the Needles, the first two hours were an arrow straight course, despite a tide of 1.8 knots trying to push the boat to the west. His movement to the east was due to "human intervention" :-) The design of the autopilot, including the software, that runs on the picaxe, is on the linked page www.gpss.co.uk/rbdesign.htm You will read that "confused by the tide" would result in the boat drifting with the tide, due to it applying so much rudder to counteract it, that it ends up going in circles, and hence drifts with the tide. But, despite my worries, that did not happen. Oh yes, not all the evidence on who snatched Snoopy is public - but there is enough there to give a clue :-)

    p.s. see "launch before Christmas to attempt the Atlantic crossing from UK to USA ? ... " on www.gpss.co.uk/rb11to12.htm
    Last edited by Robin Lovelock; 02-04-2013 at 20:25. Reason: p.s. added

  3. #253
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    Quote Originally Posted by JimPerry View Post
    I have a couple of different boards which I will be testing over the next few weeks - also have a mechanical and electronic compass to check calibration with!
    Crikey! It's a while since I visited this thread. My reason is that I've just ordered another three PICAXE servo controller kits, to make up another spare SPOT tracker, for "boat 10" (for launch in 2014???). Boat 9 is still ready for another attempt this year. For latest news, see www.gpss.co.uk/autop.htm

    Stopped laughing yet ? :-) Reason for this post is to contact Jim again - any progress on that compass ? When I ordered the picaxe kits, bundled in with the faster 08M2 chip, I just saw that it supports the I2C protocol - so - if power consumption is not a problem - the compass might be easy to interface from a software point of view.

    Robin
    www.gpss.co.uk

  4. #254
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    Yes I've got them - and will be doing work soon - with a break in and house sale I've been a bit preoccupied
    Time is natures way of stopping everything going wrong at once

  5. #255
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    Sounds Good Jim. Sorry to hear about your other "diversions". I wonder if one of your chips is the Proto-pic HMC6352 at £24 ?
    I found nice words from me on Page 20 of this thread, when I cancelled an order - they were very nice about it.
    I googled and found their page http://proto-pic.co.uk/compass-module-hmc6352/ - looks great: 2.7v - 5.2v and only 1mA.
    Maybe the I2C is not a problem now, on my 08M2 based based Picaxe AXE024 servo controller. Maybe has not been a problem for the past year :-)

  6. #256
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    I've just ordered two of those Proto-Pic compass modules, and hope to start trying one out in a few days, on a PICAXE servo controller with Servo, to see if I can get a low power "steering subsystem" working. No harm in starting to work on whatever goes into the next boat after that waiting here to launch :-) www.gpss.co.uk/autop.htm

  7. #257
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    Robin: What an amazing long-term project. It's amazing to see your efforts and enthusiasm over so many years. Hoping your weather window comes soon, followed by an amazing trans-Atlantic journey. My brother has a sailboat in Oriental, NC. Whenever your bot makes it that far, I'm sure he'd love to plot an intercept course and escort Snoopy into the colonies.

    erco

  8. #258
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    Quote Originally Posted by Robin Lovelock View Post
    I've just ordered two of those Proto-Pic compass modules, and hope to start trying one out in a few days, on a PICAXE servo controller with Servo, to see if I can get a low power "steering subsystem" working. No harm in starting to work on whatever goes into the next boat after that waiting here to launch :-) www.gpss.co.uk/autop.htm
    Quite easy to do, but will require some floating point maths to extract the X, Y and Z parameters.

  9. #259
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    Hi Folks. First I'll paste some relevant links in below, such as the datasheet for the HMC6352 Compass Module.
    I'm hoping some of you, maybe even Hippy, will save me some time getting this Compass working with my Autopilot.
    Two compass chips arrived this morning - one to test and a spare, in case I blow it up !

    I'll start with a few words to put this into context: this thread started just over two years ago, when I started the process
    of moving from a Pocket PC autopilot, to one based on a single PICAXE. I had been using PICAXE as servo controllers,
    long before, and had - with help from Hippy and others - solved problems like reading the GPS serial data.
    This was a great success, and we were soon into tests on water. This simple GPS-Picaxe-rudder servo
    has been thoroughly tested, including months of 24/7 tests, and GPS simulation across the Atlantic.
    If you read my "front page" below you can amuse yourself with the details.
    The "design" page goes into more detail on how it was put together. See bottom of page for mention of the compass.

    Now, while waiting for a suitable launch window, I'm working on what might find it's way into a future design,
    such as that used in next year's boat. If the work goes well, it may be tested on the water within days or weeks,
    and - after the required few months of water tests, including 24/7 tests - it may get adopted for the next boat.

    Possible benefits of using the compass, instead - or in addition to - GPS based heading, are potential reduced power consumption
    and not being "confused by the tide" - although our November launch indicates this is not a problem.
    There may be other spin-offs for 24/7 testing, like the boat steering in much lower wind speeds.
    If the wind drops to 1 or 2 mph, the boat drifts into the bank, due to GPS based heading being too inaccurate.
    This costs me petrol, going over to Bray Lake next morning, to push it out again :-)

    I'll be starting simply, with a the compass chip, PICAXE servo controller, and a servo.
    If I'm lucky, it may be possible (if we have enough pins?) to interface the compass into the existing PICAXE Autopilot.
    If not, we might split the system into the "GPS Navigation PICAXE" and the "Steering PICAXE".
    So "how many pins" and "which pins to use" could be important decisions when I start.

    I do hope G6ejd is very wrong above. Take a look at the datasheet for the Compass chip below. I intend to use this in the simple mode of outputing (maybe at 2 Hz) compass heading - not that X,Y,Z option. Also, if I'm lucky, I'm hoping to set this startup mode into the EPROM, which means I will only need one pin on the picaxe. Before you rush to talk about "tilt compensation" - I expect to test this as quickly as possible in realistic water conditions, with the boat leaning over and bobbing about.

    I'll obviously be starting "on the table", with the compass connected to the PICAXE, but should then quickly progress to "walking around outside the house" between two waypoint, checking that the servo is moved correctly. Soon after that, it will be tested on Bray Lake, doing the "Bray Lake Test".

    But lots of things may jump out to bite me before then :-)

    Robin
    www.gpss.co.uk
    www.gpss.co.uk/autop.htm - robot boat "front page" with latest news, etc. Amusing videos :-)
    www.gpss.co.uk/rbdesign.htm - what serves as a "design" page, including the picaxe based autopilot
    http://www.sparkfun.com/datasheets/C...ts/HMC6352.pdf - data sheet for HMC6352 Compass Module
    http://www.picaxe.com/docs/axe024.pdf - PICAXE AXE024 Servo Controller kit

  10. #260
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    Hi Folks. Looks like I need help sooner than expected - where to find SCL pin for I2C on the AXE024 ? :-)

    I nearly got the HMC6352 a few months ago, but then saw it was I2C - not simple "RS232" serial (supported by SERIN/SEROUT)
    Then, more recently, I saw that the faster chip in my AXE024 Servo Controller kit DID support I2c. (e.g. READI2C)

    I've added some info on my "design" page above, on existing uses of pins, for things like GPS input, servo output, etc.
    It seems I might start by adding one or two male servo leads onto the Compass Module to take it's 4 wires
    (Power +5v and 0v, and SDA (data) and SCL (clock) to the right place on the PICAXE board.
    BUT Where ? Particularly for the SCL pin ?

    Before someone says "use a different PICAXE kit" I'd like to have it confirmed it is not possible with the AXE024 Servo Controller.
    But I'm hoping it is.

    Robin
    www.gpss.co.uk

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