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Thread: Dive CAN/ISCAN/CAN Bus - what's the fuss?

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    Re: Dive CAN/ISCAN/CAN Bus - what's the fuss?

    Upgradability and the "plug and play" nature of quick repairs are certainly enticing. But the reality is that it does add a significant degree of complexity and failure points. Reliability of each component is therefore critical.

    In the old days when something went wrong with the engine in my car, it was probably the plugs, points or distributor. Lots of fiddling and adjusting required. Now it is a billion little relays and electronic components that you just pop in a replacement. As long as you have the multi-thousand dollar computer that is necessary to tell you which component went bad.

    Digital has its advantages and also its drawbacks.
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    Dive CAN/ISCAN/CAN Bus - what's the fuss?

    I'm in the same boat as most divers as knowledge of this Dive Can is very limited. John mention it has the ability of "plug & play" but does it. Meg. and rEvo both can be bought with the new Dive Can system and now Optima has joined the list. My question is can I take the Shearwater Petrel that say came with a Meg and swap it over to a rEvo using the new Wet Connectors or have the manufactures have it where only the electronics manufactured for them can be used?


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    Re: Dive CAN/ISCAN/CAN Bus - what's the fuss?

    Quote Originally Posted by SlowDiver  View Original Post
    I'm in the same boat as most divers as knowledge of this Dive Can is very limited. John mention it has the ability of "plug & play" but does it. Meg. and rEvo both can be bought with the new Dive Can system and now Optima has joined the list. My question is can I take the Shearwater Petrel that say came with a Meg and swap it over to a rEvo using the new Wet Connectors or have the manufactures have it where only the electronics manufactured for them can be used?


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    I was wondering the same thing. I think all the can bus rebreathers are using petrels as controllers. Is each manufacturers system actually different coding, or just different marketing? I would think it would be a pretty easy thing to add an ID code or something so that revo controllers only worked with revos, so the systems could be 99.9% the same, but still coded to a specific brand.

    That would limit options for upgrading to anything but OEM or approved parts. Thats fine as long as everything is working but what happens when a part goes tits-up and you can't replace it... is your rebreather dead? I'm thinking of a problem like AP O2 cells, not a broken part that just needs to be replaced.

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    Re: Re: Dive CAN/ISCAN/CAN Bus - what's the fuss?

    Quote Originally Posted by sea_ledford  View Original Post
    I think all the can bus rebreathers are using petrels as controllers. Is each manufacturers system actually different coding, or just different marketing?
    My rEvo came with a SW Predator (early 2013). I don't think there is a rMS system on any other rebreather yet, so clearly the code handling that info will be of no use on a different unit. So apparently the code IS different.
    On the other hand, when I upgraded to the latest firmware, I was not asked whether I wanted the version for the rEvo w/o rMS or that for the Titan, or anything else.
    However, I doubt that the interface side of the code is grabbed from the DiveCAN modules, so it has to be here but only activated when sensed.
    If I disconnect all modules (O2, solenoid and battery), they disappear from the 'Bus Devices+' menu, but the interface remains otherwise identical. It detects the absence of these modules (and let you know about it in no ambiguous way on the main screen), but it doesn't rebuild its interface on the fly when you boot up the Predator w/o the other modules connected.
    For instance, I can go to the rMS menu items and there is nothing to see there (except for the basic rMS log), exactly like when my rMS acted up in the past.
    So to me it seems that SW does package different versions of the code in the same firmware bundle and only uploads the one that is appropriate for the SW hardware unit. In other words, my SW is hardwired to be used in a rEvo rMS and will always assume it is connected to one.
    Not only that, but if I connect the solenoid board to the battery cable, the battery to the O2 cable and the O2 board to the solenoid cable, only one board appears to be detected, the solenoid one. So, again w/o any guarantee of this being correct, it appears that the 'plug wherever and go play' doesn't seem to mean what some say it does, at least in the rEvo case.

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    Re: Dive CAN/ISCAN/CAN Bus - what's the fuss?

    Quote Originally Posted by sea_ledford  View Original Post
    That would limit options for upgrading to anything but OEM or approved parts. Thats fine as long as everything is working but what happens when a part goes tits-up and you can't replace it... is your rebreather dead? I'm thinking of a problem like AP O2 cells, not a broken part that just needs to be replaced.
    Well yes and thats exactly what they want, JJ wants you to buy a JJ Petre, rEvo wants you to buy a rEvo Petrel, Shearwater supplies DiveCAN OEM parts only to Manufacturers... all for a good reason because they want to ensure the integrity of their system and make sure you use the proper parts.

    Quote Originally Posted by Sambo  View Original Post
    Here is a quote from Paul R from another thread on this forum
    "are you sure the unit was 'OFF' when you removed the controller? if not the unit tries to keep you alive, as it has PPO2 and can fire the solenoid, it does not need the handset"

    So it is implemented already. Of course like you say, if you have no back up ppo2 display (all canbus rEvos come with a backup ppo2 display) you need to bail out. Be assured there are not 2 masters! The handset is the master and the can bus modules are the slaves but after the master has given the command, the slaves can work together to achieve the goal of the master while he is away :)

    If you dont trust a black box (with a working ppo2 display) you better not be diving on any electronic unit as they all have a "Black Box"
    Yes correctly I would always want to verify one system with another, rEvo is imho the best on that with two dreams and the DiveCAN controller you have two very independent systems to verify against each other. Even with the Petrel dead the Cell/Solenoid Boards maintaining PO2 and the Dreams I still have a fully working system to finish Deco on it. Thats the main weak point on the JJ imho its relying fully on the Bus with Petrel and HUD being DiveCAN now from what I have seen? Although I am giving the DiveCan system a bit more credit, as it has not increased complexity for the diver, the system might got more complex, but it added also safety in terms of digital data transmission, message and information integrity...

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    Re: Dive CAN/ISCAN/CAN Bus - what's the fuss?

    Quote Originally Posted by SlowDiver  View Original Post
    I'm in the same boat as most divers as knowledge of this Dive Can is very limited. John mention it has the ability of "plug & play" but does it. Meg. and rEvo both can be bought with the new Dive Can system and now Optima has joined the list. My question is can I take the Shearwater Petrel that say came with a Meg and swap it over to a rEvo using the new Wet Connectors or have the manufactures have it where only the electronics manufactured for them can be used?


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    The answer is no for swapping, because they use different size wet connectors.

  7. #17
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    Re: Dive CAN/ISCAN/CAN Bus - what's the fuss?

    It seems we haven't done of very good job of explaining DiveCAN. I will try to clarify some issues that don't appear to be very well understood. I aplologize in advance for the length.

    First is the belief that DiveCAN is the first instance of using digital communications on a rebreather. I would say that almost the reverse is true. Many rebreathers use serial communications to the handsets. At least one rebreather uses I2C. All rebreathers convert to digital at some point, because all of the processing is digital. Other rebreathers use multiple modules that communicate digitally.

    The world has gone digital because it offers so many advantages. Cell phones were all analog in the early days, but you won't find one now.

    So given that digital communications are ubiquitous, we started thinking about the best way to do it. We looked at basic serial and at higher level serial like HDLC and SDLC. We looked on microprocessor communication protocols like I2C and SPI. We looked at internet protocols like Ethernet. We looked at process control protocols like DeviceNet and Modbus. We looked at vehicle protocols like CAN, MilCAN, and NMEA 2000.

    In the end, the extremely robust CAN protocol won. It can operate in very electrically noisy environments like a car or semi-trailer. It is suitable for high speed device control like brake-by-wire in cars and turret aiming in tanks. It allows very long cable lengths for surface control applications. It has predictable latency with high traffic, unlike Ethernet. The protocol handler is built into the hardware of the ARM microprocessors that interest us, and the cable level transceiver handlers are inexpensive and used by the millions by the automotive industry so will always be available. Finally, CAN was designed to be a platform that would be used to support a message structure like NMEA 2000 and J1939, and that was exactly what we wanted.

    Shearwater started in the rebreather control business, and only started making stand-alone computers years later. We have always been focused on the needs of technical and rebreather divers. We have always pursued high reliability in our products. There is almost nothing worse for a diver than being in Truk Lagoon or Bikini Atol, or having trekked in the forests to find a particular cave, and then having your rebreather electronics fail. One of the biggest reasons for DiveCAN is that it allows the diver to take spares and repair in the field.

    Another issue that we face is that electronics change fast. Processors and displays get discontinued. New technologies arrive that run faster using less power. Prices of new functionality drops. To support this trend, we wanted the ability to adopt new technology without forcing the diver to replace his rebreather. This dictated modules that could be independently replaced.

    In addition to the above reasons, there are real advantages to the use of independent, mutually suspicious, modules. For example, in a DiveCAN system, the handset battery can die and the solenoid board will continue to read the sensors and fire the solenoid. It will automatically switch to a .7 setpoint which works for any depth. If the handset notices that the solenoid battery is low, it can start to provide power to the head board so that it can at least read the oxygen sensors even if there isn't enough power to fire the solenoid. In other words, it is able to detect that there is a system degradation and do something useful to minimize the impact.

    The logging systems can now be autonomous. Each module can log the messages from the other modules so that even if a module is malfunctioning, it is still having its messages, or lack of messages, logged.

    Each rebreather has two independent DiveCAN buses, or a DiveCAN bus and some other secondary. One DiveCAN bus is the control bus and the second is the monitor bus. Because each rebreather is different, and rebreather manufacturers have different visions of how things should work, the control bus is proprietary. The handset must be configured for the rebreather. This means that the controller is not interchangeable between manufacturers. As already mentioned by someone, an rMS system has to know to look for temperature sensors and display an error if they aren't present. We think it is a huge step forward from the permanently attached handsets on all rebreathers before DiveCAN. Now a controller can be replaced in the field.

    On the monitor bus, there is no need to be proprietary. We offer multiple options for the monitor bus, and more will follow. Each of these monitor devices can be connected to any DiveCAN rebreather.

    The DiveCAN protocol is the result of years of work since we announced our intentions to our OEM manufacturers in 2009. During the process we did a joint development program with ISC and we support ISCAN monitor devices. We have entered discussions with another manufacturer for joint development, but it did not proceeded into a project.

    While we hope that DiveCAN becomes a standard in the industry, we make no promise about when or if it will become publicly available. As anyone who has been involved in a standardization process will know, that is a long and winding road.
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    Re: Dive CAN/ISCAN/CAN Bus - what's the fuss?

    ​Guys ... I've just gone through this heartache. I am afraid to me the situation was/is not very clear, maybe through my ignorance or the suppliers need to be more precise with just what is on offer.

    Let me use a Nerd as an example of the problems we have.

    I have customers that want to install Nerd's on JJ's to replace the old HUD and any second computer system that may be already installed, this is where we ran into problems with the analog/digital thing.

    A std. Nerd with the fischer cable will fit onto a JJ head if you install an entry port for the O2 cell cables and provide a female Fischer connection ... all good there not an issue the Nerd just plugs in. Buy the Nerd from a Shearwater supplier and fit it - easy! Disconnect your secondary computer via the Fischer cable and plug in the Nerd. You cannot though remove the HUD - so just tuck it away some place on the unit and forget it (shame that in my view, you be able to remove it completely ).

    A DiveCam Nerd is a special order though and you need to get them from the CCR manufacture as Shearweater does not supply to you as a retailer direct. It also appears that each manufacture is using different plugs ... we need to confirm this - anybody know this to be 100% true ???

    You also cannot cut the Fischer connection off the std. Nerd cable and then install a digital plug so that it will fit into the DiveCan JJ head.

    In our case and given that JJ only produce DiveCan units, it now means that I must order the unit with a special digital Nerd or order the digital Nerd afterwards from JJ. This Nerd will simply replace the HUD. So plug and play.

    What I would like to know is can you now plug that same digital Nerd into any other digital unit or do we have to make adaptors or are we stuffed and have to order a new unit specific Nerd each time???

    regards Baz

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    Re: Dive CAN/ISCAN/CAN Bus - what's the fuss?

    Quote Originally Posted by Bazza  View Original Post
    ​Guys ...

    What I would like to know is can you now plug that same digital Nerd into any other digital unit or do we have to make adaptors or are we stuffed and have to order a new unit specific Nerd each time???

    regards Baz
    A DiveCAN NERD monitor can plug into any DiveCAN monitor port.

    A DiveCAN NERD controller is proprietary and is specific to the rebreather.

    In general, the control bus is rebreather specific and the monitor port is standard. Keep in mind that the rebreather manufacturer may have one standard configuration due to CE requirements.

    ISC uses ISCAN and neither the connector nor the CAN implementation is compatible with DiveCAN.
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    Re: Dive CAN/ISCAN/CAN Bus - what's the fuss?

    My experience with ISCan is a mixed bag of nuts:

    The bad: It is mostly "promise or vapor" ware. Sure, the technology may allow you to plug in extra doo-dads such as pressure sensors, SPG sensors, backup computers, huds, etc. The truth is that these extras are not available yet or even visible in the market. Owing to the proprietary nature of the interface, customers are dependant solely on ISC for producing them. Sad really. Proprietary crap kills the innovation.

    Although Blue-tooth is built-in, no software is available from ISC to use it! Even if they did provide the software, a manual from ISC is just too much to ask for so you couldn't use it anyway.

    The handset has an 8gb micro SD card in it. I wonder what it stores on there and how to access??



    The neutral: the system turns on whenever water hits the plug contacts. Even with no handset/hud plugged in, you can still jump in the water and have the unit maintain the last setpoint. The downside of this is that the unit tends to turn on if you just look at it sideways. This depletes your battery in-between dives. I've gone through way too many batteries this way.

    The good: You can plug your hud into your secondary slot and have a fully independent system without a second handset. Calibration is for each device so you can move them around.

    The head can be powered (for cell readings only) via the handset/bus. This might give you some time after your head battery fails to figure out what is going on. Too bad you can't control the solenoid from the second head battery. If you could, you would be able to swap the handset over to the other plug and continue diving. Primary and secondary systems are two completely separate CANbus systems that don't talk to each other. There must be a splitter right next to the cell inputs to maximize redundancy...

    Who will be our hero and be the first to jailbreak the ISCan system?

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