| mit | Posted: 29 Feb 2020, 12:09 PM |
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 yeah whatever Admin Posts: 566 Joined: 4-May 16 |
It's unlikely I'll have the time to make a new version of the clock soon, but I figured I'd make a list of things I'd like the next version of the clock to feature. Direct drive display so that there's no flicker even at 10,000 FPS. I want every segment to light up with microsecond accuracy. There are a couple of approaches here but the easiest is probably to just get a stupidly big microcontroller with at least 130 GPIO pins so it can directly control all of them. Another option, but a more expensive one, would be to use an FPGA. That would be a fun learning experience, and would let us update every digit within the same clock cycle. There are other ways, like linking together multiple small or medium sized chips, or using old BCD to 7-segment decoder chips to reduce the needed pincount, but seeing as you can get a STM32H743 for ~$10 I think I might just use that. It's got 140 GPIO pins and runs at an insane 480MHz. Read out to 1ms (or better) - No one has asked for this, but I want it. If we do the direct drive it'd be trivial to add more digits on the end. Autoconfig Possibly the most wanted feature. The clock should use GPS to find the timezone you're in. The problem is the database is huge and takes a lot of calculation (for a little microcontroller) to parse. If we switched to a much bigger micro, this is less of a problem. We could even put linux on it. But there's still the problem that the timezone borders move and daylight saving rules change. So it has to be updatable. We got three options, either we give it internet access (lame), we stick an SD card on it, or we add a USB port that acts as a mass storage device. Possibly it just shows a config.txt that you could edit. I like the idea of an SD card because we could just dump the whole database on there and it'd be easy to update. It'd be easy to make it so you just enter the timezone via buttons on the back, but that would be lame. It also wouldn't fix the DST problem unless we got rid of DST and just let the user move the clock forwards and backwards manually. That feels like a step backwards. Toggle switch between UTC and local time I think a blog incorrectly stated that the clock could do this, so a few people were expecting it. It hadn't occurred to me as a feature but it would be easy to add, and useful for a lot of ham radio people. If we add any kind of controls to the clock at all, we might as well let you scroll through a list of cities and display the time in each one (assuming we do add the TZ database) For both autoconfig and this, we need a way to display the timezone too. Possibly this means extra digits (a +00:00 on the end of the clock would comply to ISO8601) but I don't really want to make the clock wider... Battery-backed temperature compensated RTC Easy to add and would keep good time while the clock is turned off. All SMD assembly I think maybe forget it being a kit, and update the design so it can be pick-and-place assembled. Quite a lot of people wanted a clock but told me they didn't know how to solder. I shied away from selling a complete kit just cause I thought there might be regulation and certification that a kit isn't subject to... but maybe I'm worrying about nothing. Replace Digits with easily-sourced SMD LEDs This might sound stupid but I've wasted so much of my life trying to buy those 1-inch seven segment displays. It seems buying them 500 at a time is almost impossible, and the manufacturers do a terrible job of describing their product, nothing more disheartening to find that your shipment from China turns out to contain the wrong parts. SMD LEDs on the other hand are extremely cheap, always available both locally and from China, and can be reflow soldered. So this would substantially reduce the production cost of the clock. The problem is we'd have to build our own diffuser and it might look rubbish compared to the current clock. I think if I expand on the tactic used to make the DST window in the middle, maybe we could do the whole clock like that. Only experimentation will give us the answer. -- Phew - if anyone has any comments or ideas feel free to chuck them at me here. Last edit by mit at 29 Feb 2020, 12:09 PM ------------- |
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| mit | Posted: 29 Feb 2020, 01:06 PM |
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yeah whatever Admin Posts: 566 Joined: 4-May 16 |
Just thought of a few more things Day of year was requested a few times. The ISO8601 way of writing it would be 2020-060 (instead of 2020-02-29). Just need to remember to wire up the 8th digit fully to allow that. Different colours requested by multiple people. The hassle of sourcing digits has held me back, but if we switched to SMD LEDs and a diffuser this is easy. Forgot to mention that direct drive of the segments is going to make brightness control a concern. PWM is right out. Either we do some crazy current mirroring with a transistor for every segment, or maybe we can get away with driving them all at constant voltage. It's not going to be particularly linear but we could compensate for that, especially if it's controlled by the uC. ------------- |
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