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.

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)

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)

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@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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