Every now and then I think about small spectrometers (my university final year project was one). Today I'm thinking about ways to have a battery-powered spectrometer communicate with a smart device.

The way I did it in the project was to host a web server on the spectrometer and have it act as a WiFi hotspot. This seems massively overcomplicated and gave me an intense dislike of creating webapps.

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Possible reasons to *want* to connect a spectrometer to the smart device:

- Minimise the UI on the spectrometer (this may not be a good goal, but it would help to reduce the cost of the spec itself to the user)

- Do more processing of the data. I'm not sure how much analysis you'd *want *to do without a PC though.

- Simplify the spectrometer itself (but you're just shifting the complexity elsewhere)

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Ways I've thought of to do this:

- Bluetooth - not a lot less complicated than Wifi, but maybe less icky? Tens/hundreds of kbps

- Audio - either over a cable (RIP 3.5mm jacks) or coupling through the air (susceptible to external noise). Basically work like an audio modem. Tens of kbps

- Light! - Use camera screen to transmit to photosensor on spec, use light on spec to transmit to camera on device. Data rate is probably LOW (~60bps)

The audio method is made complicated by the fact that phones have got rid of headphone jacks, but I still like it.

I think the light method is hella cool, and there are probably ways to minimise the transmitted data and make it faster than my initial estimate. (LED matrix?)

Now I've written it down I'm not sure why I've been thinking so much about offloading the UI to a touchscreen. I almost always prefer a physical UI and it's what I like to design, so why don't I do that?

I think I just talked myself into yet another project before finishing the last two.

On the subject of "more button is more better", the reason I haven't finished off the electro-sax project is because I want to get the buttons right.

Capacitive buttons are just too much of a pain. I need to keep recalibrating or they go all fucky.

The only problem I had with using the Cherry MX style switches was their activation point being too early. I reckon that could be fixed with a custom slider (if I had access to a resin printer to get the quality I need)

The idea I'm toying with is basically making my own switch. You just have the mechanical part complete a circuit, maybe to something like a battery contact.

There's already a lever I'm pressing down, and I want the activation point to be when the lever is fully down. Why not simplify the whole thing to a switch matrix again?

The only problem I've had so far is finding the right spring/contact for it to hit. I know it exists somewhere, I just need to find it.

@piggo More button is more better. I need to think about the actual use case for this a bit. I only know one person who actually uses a spectrometer! (the chemist who set the brief for the project)

But yeah, encoder knobs are super nice (especially those oven ones you can push in so they don't stick out when not in use)

@gbrnt I wondered if animated QR codes for data transfer were a thing, and it seems someone did it already divan.dev/posts/animatedqr/

@sfcgeorge That's awesome, and yeah a QR code sounds good for visually transferring data! I'm a bit wary of the inbuilt complexity (image recognition stuff is required but is obviously built into phone OSes). That transfer rate is great though - even with a smaller QR code on a lower resolution screen it'd be plenty!

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