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Search for an inexpensive rec computer running Buhlmann

Discussion in 'Computers, Gauges, Watches and Analyzers' started by scubadada, Dec 5, 2019.

  1. wetb4igetinthewater

    wetb4igetinthewater Instructor, Scuba

    # of Dives: 500 - 999
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  2. dmaziuk

    dmaziuk Orca

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    They're running Buhlmann's formula in a loop I'm sure. You can get clever and do a binary search instead of simple-stupid adding one minute every time, increase recalculation interval and probably come up with some other juice-saving tricks too. But it's a backlit dot-matrix screen with the GPU and so on, so its "amazing" doesn't compare with 2 years on a CR24xx anyway.
     
  3. wetb4igetinthewater

    wetb4igetinthewater Instructor, Scuba

    # of Dives: 500 - 999
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    It's pretty darn amazing compared to the Aeris A300 CS that I used to have! lol.

    Yeah, my old Oceanic Pro Plus 2.1 had much better battery life. But given the time that I don't have to recharge the batteries on my Perdixes (Perdices?), it is more than good enough. If I have to charge my DC more often than my dive lights, then Houston, we've got a problem.
     
  4. dmaziuk

    dmaziuk Orca

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    Atmos has 40 dive-hours "no backlight" in their sales spiel, way better than cosmiq's 12. MIP screens do help a lot.
     
  5. scubadada

    scubadada Diver Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Philadelphia and Boynton Beach
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    Wow, from the owner's manual, looks like you can custom set GF high and GF low. That would be a real breakthrough, if true. Keep in mind this is another Taiwanese offering, like the Deepblu Cosmiq+. Maybe they got it right? The Watoom Cyano was from South Korea

    Edit: corrected information, thanks to @runsongas .
     
  6. KenGordon

    KenGordon Rebreather Pilot

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    You don’t need anything like a GPU to drive a dot matrix display. 10 years ago when I was building stuff with displays the display itself could have a framestore addressed by tiny messages saying ‘write these bytes here’ . This was all about power consumption for very small phones. All it has to do is clock a few 10k bytes out 60 times a second, often you can get away with slower than that, and so even less power.

    cpu wise you are looking at the odd few hundred multiply and adds per iteration, then dozens of compares. This processor is 32mhz, a bit tight on flash but $1 10k off, uses 49uA/MHz so 1.6mA flat out. STM32L0 Series - STMicroelectronics
    But mostly it would be asleep using 100s nA. The display and pressure sensor would dominate the power draw. Some of this family has direct drive for small screens, no glue required.

    When I was having my head electronics replaced recently I got to see the inside of a variety of high end computers in for repair, they were using older versions of the same family. The OSTC Buhlmann implementation was for a small 8 bit processor.
     
  7. wetb4igetinthewater

    wetb4igetinthewater Instructor, Scuba

    # of Dives: 500 - 999
    Location: Seattle
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    Ken,

    Great point on sleep time for the processor. I forgot that human time and CPU time are on completely different scales so that such a processor (which I use at work) is asleep most of the time. So in terms of the power budget, the CPU is going to be a small fraction.
     
  8. runsongas

    runsongas Great White

    # of Dives: 500 - 999
    Location: California - Bay Area
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    taiwanese according to their site, same as deepblu
     
    scubadada likes this.
  9. dmaziuk

    dmaziuk Orca

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    @KenGordon: you don't need an Nvidia-level GPU to drive a display, but you need the chips to translate what you write to your framebuffer to the actual lit-up pixels. As opposed to just "turn this LCD segment black" from the bad old days. And all of that takes juice.
     
  10. KenGordon

    KenGordon Rebreather Pilot

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    Still only the odd 100uA. The cpu and display driver will be less that the led that tells you the thing is on. The real consumer is the screen backlight and maybe the pressure sensor. This is why Zoops etc all go for years on one coin cell.

    There is a big brother to the STM32L0 which includes lcd driving logic and it is still only 90uA/MHz.
     

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