4 ms·

Does this work inside? How cheap is cheap?

mytailorisrich 3y ago
> Does this work inside It depends. Hence my previous comment. > How cheap is cheap? Google says unit retail price for module with PPS output can be under $5.
- peteforde 3y ago
  Our deployment environments were occasionally in places where daylight wasn't a thing. However, if we could have used GPS at a marginal cost of $5 at the time, it's very likely we would have been excited to hear about this. Thanks for the lightbulb moment.
  - stavros 3y ago
    Would it have worked to add something like a single GPS module connected to an ESP8266 that sends a pulse every minute to all the Pis' GPIOs so they can sync?
    - peteforde 3y ago
      We tried something like this, up to a pulse a second, and it’s hard to stress how crazy you can get trying to make physics behave differently.
      - stavros 3y ago
        What went wrong there? Surely the pulse propagated at close to the speed of light? What kind of synchronization accuracy did you need?
        peteforde 3y ago
        <1ms The internal "clock" time would start to drift immediately after it was set.
        stavros 3y ago
        Hm, yeah, you'd need a much more frequent method of synchronization to avoid that. I'm assuming the rate wasn't constant, huh? Because of voltage drops depending on draw?
        peteforde 3y ago
        I want to be a better conversation partner on this, but I am extremely constrained in what I can share and again, it was 8-9 years ago that this was all top of mind. Can we mutually agree that in a year of not-dumb people trying everything we could manage to achieve the best outcome, we tried a lot of things and we often didn't know what we didn't know?
        stavros 3y ago
        We cannot, because I'm not trying to find you a solution you didn't think of, I'm trying to learn from your failures so I can skip over them next time I need something similar to this.
        peteforde 3y ago
        First, our failures were not technical. We succeeded at creating a sub-$100 camera node that could be replicated and/or replaced quickly by relatively unskilled talent. If I was going to do it all over again with the decade of engineering skills I've learned, I would look towards fabbing our own RTC I2C daughterboards and trying some GPIO-based approaches to triggering. However, given our constraints, the solution I've described above worked incredibly well. I wouldn't be embarrassed to do it again.
        stavros 3y ago
magicalhippo 3y ago
> Does this work inside? Mine does after I got an active antenna for it. > How cheap is cheap? I got a u-blox NEO-6m module for a few bucks, add another few bucks for the active antenna. The newer GPS modules are much better (more satellites, faster lock etc) but this is sufficient for me.

> Does this work inside It depends. Hence my previous comment. > How cheap is cheap? Google says unit retail price for module with PPS output can be under $5.

peteforde 3y ago
Our deployment environments were occasionally in places where daylight wasn't a thing. However, if we could have used GPS at a marginal cost of $5 at the time, it's very likely we would have been excited to hear about this. Thanks for the lightbulb moment.
- stavros 3y ago
  Would it have worked to add something like a single GPS module connected to an ESP8266 that sends a pulse every minute to all the Pis' GPIOs so they can sync?
  - peteforde 3y ago
    We tried something like this, up to a pulse a second, and it’s hard to stress how crazy you can get trying to make physics behave differently.
    - stavros 3y ago
      What went wrong there? Surely the pulse propagated at close to the speed of light? What kind of synchronization accuracy did you need?
      - peteforde 3y ago
        <1ms The internal "clock" time would start to drift immediately after it was set.
        stavros 3y ago
        Hm, yeah, you'd need a much more frequent method of synchronization to avoid that. I'm assuming the rate wasn't constant, huh? Because of voltage drops depending on draw?
        peteforde 3y ago
        I want to be a better conversation partner on this, but I am extremely constrained in what I can share and again, it was 8-9 years ago that this was all top of mind. Can we mutually agree that in a year of not-dumb people trying everything we could manage to achieve the best outcome, we tried a lot of things and we often didn't know what we didn't know?
        stavros 3y ago
        We cannot, because I'm not trying to find you a solution you didn't think of, I'm trying to learn from your failures so I can skip over them next time I need something similar to this.
        peteforde 3y ago
        First, our failures were not technical. We succeeded at creating a sub-$100 camera node that could be replicated and/or replaced quickly by relatively unskilled talent. If I was going to do it all over again with the decade of engineering skills I've learned, I would look towards fabbing our own RTC I2C daughterboards and trying some GPIO-based approaches to triggering. However, given our constraints, the solution I've described above worked incredibly well. I wouldn't be embarrassed to do it again.
        stavros 3y ago

magicalhippo 3y ago

> Does this work inside? Mine does after I got an active antenna for it. > How cheap is cheap? I got a u-blox NEO-6m module for a few bucks, add another few bucks for the active antenna. The newer GPS modules are much better (more satellites, faster lock etc) but this is sufficient for me.