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Anyone looked at Shearwater CANBus Protocol?

Discussion in 'Rebreather Diving' started by telemonster, Oct 13, 2020.

  1. telemonster

    telemonster Barracuda

    # of Dives: 100 - 199
    Location: Northern Virginia
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    Has anyone poked at the Shearwater CANBus protocol?

    I have a Prism2 and always wondered about something like a DIY NERD2 that only has PPo2 and depth information on it. There are some cheap OLED Color screens out there that are tiny. Microcontrollers with CANBus are cheap. The optics side is a bit more tough, as is housing. Maybe also add an offset motor if the PPo2 values fall too far out of line (in the red.)

    I love the NERD units but the DIY side in me is curious (plus price point is rough.)
     
    tridacna likes this.
  2. kelemvor

    kelemvor Big Fleshy Monster ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Largo, FL USA
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    telemonster and tridacna like this.
  3. telemonster

    telemonster Barracuda

    # of Dives: 100 - 199
    Location: Northern Virginia
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    Oh interesting! I wish that diagram was in the Prism2 manual. The people I asked didn't know how things were laid out inside (System architecture) so I ended up taking the unit apart to see.

    I asked if the protocol was open at the DC Dive Show and was told no. I doubt they want work-a-like products available, or devices that could cause problems. Or people asking for support on things that aren't generating revenue for them.

    Also, they tend to only do deals with manufacturers for their CCR electronics AFAIK. They don't sell the control electronics as generic kits to convert non-Shearwater units and homebuilds.
     
    Bigbella likes this.
  4. telemonster

    telemonster Barracuda

    # of Dives: 100 - 199
    Location: Northern Virginia
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    CanBUS tools on the way. Will report what I find once they arrive and I get a chance to poke at it.
     
  5. kelemvor

    kelemvor Big Fleshy Monster ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Largo, FL USA
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    What did you end up going with? My scope (dirt cheap rigol ds1054z with upgrades) doesn't include logic inputs, so I was kicking around the idea of getting a cheapie USB logic analyzer which could then be accessed with sigrok which in turn decodes CAN (and many other protocols). There's about a million options for decoding CANbus though, so I'm curious.
     
    telemonster likes this.
  6. telemonster

    telemonster Barracuda

    # of Dives: 100 - 199
    Location: Northern Virginia
    351
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    I have a similar Rigol DSO as well, with the protocol decoder unlocks. A smart friend said the decoders don't work very well. I ended up ordering a DSLogic Basic, which can use the DSView software or the Sigrok tools. Friends also pointed me to the Travis Goodspeed CANBus tools, but from quick glance they look more bent towards automotive. Huge props to Travis all around though. Seed Studio has an Arduino AVR board with CanBUS transceiver ICs on it as well, that might be a good place to prototype.

    Outside of the diving stuff most of my electronics is pretty low speed vintage computer repair or arcade/pinball machine repair so the DSLogic Basic should be good enough for my usual needs.

    I haven't looked at the connectors yet, but I think it's a 4 or 5 pin thing. Will have to figure out power and ground, then find where the data lives.

    With the 12 LED Shearwater HUD (Which is bad ass, so tiny given what it does) it does have a calibration function. So not sure if the HUD just receives the mV readings from the OBOE board and is responsible for handling the ppo2 ratio / save calibration setpoint or if it passes a message back to the OBOE board to tell it to save the values. Very impressive either way given it's size.
     
  7. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
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    @telemonster the calibration is stored in the SOLO or OBOE's, not in the displays. This allows you to actually hot swap the displays between units while diving to transfer your deco information over, but not have janky calibration information. This is used by some of the guys in the KUR on their decompression rebreathers. They'll take their monitor off of the primary unit that has been tracking live the whole dive, then plug it into the deco breather and it gives them accurate deco data. This is all validated from fixed ppO2 independent handsets, but it does work and is quite nifty.
     
    Geo7, telemonster and stuartv like this.
  8. telemonster

    telemonster Barracuda

    # of Dives: 100 - 199
    Location: Northern Virginia
    351
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    tbone1004 - Awesome info! So that means anything created to replace the HUD needs to be able to pass message back to the OBOE to trigger calibration.

    Much thanks for the info!
     

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