The 2G Raspberry Pi Smartphone

For [Tyler]’s entry to the Hackaday Prize, he’s making something that just a few years ago would be unheard of in a homebrew build. He’s making a DIY smartphone. Yes, with cheap single-board Linux computers, GSM modules, and SPI touchscreen displays, it’s possible to build your own smartphone.

Inside [Tyler]’s DIY smartphone is a Raspberry Pi Model A, a 3.5 inch touchscreen PiTFT with 480×320 resolution, and an Adafruit FONA module The connections are simple enough; the TFT is connected over SPI, and the GSM module over serial. The entire device is powered by a 1200mAh LiIon battery, charged with a powerboost board, runs an operating system written in Python capable of making calls, sending texts, and takes pictures with a Pi camera.

This is not what you would normally call a smartphone. The FONA module is 2G only, meaning you’re limited to 2G speeds and 2G networks. AT&T will be shutting down 2G networks in a little bit, although T-Mobile will be keeping them up for anyone who still has an old Nokia Brick.

That said, [Tyler]’s phone is still exactly what you want in a minimal phone: it just makes calls and receives texts, it has a camera, and unlike the Nokia, you can take it apart and repair it easily. Not that you ever had to do that with a Nokia…

32 thoughts on “The 2G Raspberry Pi Smartphone

  1. Where are the microfone ans speaker connected to? Directly to the GSM module, or to the pi? Is the serial connection fast enough to transmit the audio of a conversation?

    1. FWIW the 2G GSM CODEC sends 9600bps for voice. There’s a 14.4k optionally-supported mode for enhanced sound quality. GSM phones have been around a fair while, I guess the encoding doesn’t need too many MIPS. But as others mentioned, the module takes care of that. Wonder if there’s an option to do it yourself anyway, and feed it your own encoded audio stream?

      1. That would be the only reason to make this, although the GSM module probably will have a inbuilt function, as will have the network.

        Incidentally, I see that that module also has a FM radio receiver, I wonder if you can mod the frequency range of that. And then route the output to the microphone? Just throwing out some ideas.

  2. This is great! DIY phones have never been very beautiful or high performing, but they are an awesome and necessary steps to bring us into the future of personal cell-phoning

    1. There’s a project for freedom-lovin’ hackers of the future. An implementation of baseband. Even 2G GSM would be nice, and I guess in the range of running on something like an Atmel or other low-power MCU. Up until smartphones, mobiles were pretty stupid, even getting WAP out of some was pushing the hardware.

      3G I’d guess has more to it, so would be harder. Are the standards for these published freely? Any ARM should be up to doing that.

      The problem might be getting the parts. Nowadays the whole baseband thing is a single unit, one chip that’s enough to run the whole phone, for a lower-end phone. Stuff like the radio synthesizer I guess is all built into that, so stuff that was separate chips a decade ago is obsolete and presumably no longer manufactured, so inseparable from all the spook circuits. Though even a few hundred old parts might be enough to satisfy the market for a true privacy-geekphone.

      It might be a nice idea. Then again it doesn’t stop the network triangulating you, block that and the phone no longer works. There might be some mileage in bringing discipline to a standard phone module, just stuff like disconnecting the mic until it’s needed, cutting power under user control so you can be sure it’s really off.

      To do it without using one of the simple modules would be an effort. But having free source code for communicating with 3G or LTE would enable a lot of niche options to pop up, it would be valuable to many people, and maybe free us from having to use the pre-made modules. Approval would be a separate issue, but as long as it behaves itself, how would they ever know?

  3. If i made something like this i would use a 3g or 4g dongle instead because lets face it, who uses the phone function of a smartphone nowadays? And besides theres voip for that. I would probably skip the camera module too. Could probably get it thinner that way.

    And i doubt this kid made his own OS. I could be wrong. But seems to me he just made a interface. I would use some basic wm like ratpoison or nowm and then a bunch of bash scripts and utilitys to form the basic ui. Probably be a lot faster too.

    1. The majority of people on the world use the phone functionality.
      Most often with additional use of data of course. But still though. I think you project too much, or forget about the times you use voice.

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