ZeroPhone gives Smartphones the Raspberry (Pi)

There are several open source phones out there these days, but all of them have a downside. Hard to obtain parts, hard to solder, or difficult programming systems abound. [Arsenijs] is looking to change all that with ZeroPhone. ZeroPhone is based upon the popular Raspberry Pi Zero. The $5 price tag of the CPU module means that you can build this entire phone for around $50 USD.

The radio module in the ZeroPhone is the well known SIM800L 2G module. 2G is going away or gone in many places, so [Arsenijs] is already researching more modern devices. An ESP8266 serves as the WiFi module with an OLED screen and code in python round out this phone. Sure, it’s not a fancy graphical touchscreen, but a full desktop is just a matter of connecting a display, mouse, and keyboard.

For the security conscious, the ZeroPhone provides a unique level of control. Since this is a Raspberry Pi running Linux, you choose which modules are included in the kernel, and which software is loaded in the filesystem. And with news that we may soon have a blobless Pi, the firmware hiding in the radio modules are the only black boxes still remaining.

If a Raspberry Pi is a bit too much for you to bite off, check out this Arduino based phone. Don’t want to do any soldering? Check out what you can do with a cheap Android phone and a bit of hacking.

31 thoughts on “ZeroPhone gives Smartphones the Raspberry (Pi)

  1. Hi! I’m just doing a writeup on some design decisions, and this appears. This article is very unexpected, but quite well tells about what is this, why it appeared and how I’m making it. Some disclaimers:

    1)The boards pictured to depict the idea very well, but are still prototypes. There’ll be no magnet wire hacks required in the next revision (Murphy’s laws still apply). I’ve published the alpha boards on https://github.com/ZeroPhone/ZeroPhone-PCBs , but for the love of God don’t order them yet – there are 30 bugs to be fixed and features to be added, expect the next revision in a month.

    2) The phone won’t have a hacked powerbank glued to the side – it’s just something I’ve added in 10 minutes. There’ll be an option to use pouch cells, 18650s or, generally, whatever you want.

    3) The ESP-12 antenna won’t be sticking out in the next revision either ;-)

    Kudos to the RPi-WiFi project which’s made the WiFi connectivity of this possible! https://hackaday.io/project/8678-rpi-wifi

    I have a mailing list – subscribe on https://crimier.github.io/ZeroPhone/ , I’m doing the first newsletter today! Ask/suggest me anything here in the comments, I’ve got a lot of useful suggestions this week already.

    1. I readily admit my ignorance on the matter, but what of using a software defined radio for it? A quick search finds there are some that are ~$20 and would reach the voice frequencies, but the 2/3G go a bit over… The SDR could be combined with an FPGA or another RasPiZ if more horsepower is required for the protocols.

      1. I haven’t yet found a cheap SDR solution I could use myself, don’t think there is one. There are SDRs who say they’re capable of GSM (like LimeSDR), but all that means is hardware throughput, from what I’ve heard – it means it can be implemented, just isn’t yet. Also,the SDRs that claim they can do it are still expensive.

        In the end, I’m making a platform anyone could use with a SDR if they feel like it (it’s OSHW), but I’m not capable of implementing that myself.

        1. There is an opensource base station software for 2G: OpenBTS, there is also one for LTE: OpenAirInterface. There is a 2G baseband (client) implementation: OsmocomBB but it is not complete.

          Be careful when experimenting with this, you can seriously impair the performance of other users of the cellular network with a misbehaving client quite easily (eg, wrong timing advance, transmitting on time/frequency slots assigned to other users, clogging the random access channels, …).

          1. Openairinterface is unfortunately not truly open. It’s free(as in beer) only for research and personal use. For commercial use you need to get expensive licenses. So it’s not opensource, it just has “open” in it’s name.
            But out of the existing freely available LTE BTS implementations, it’s the best.

    2. If it helps with your research, I found the following part searches for cellular modules, when ever you have time to think about a 3G/4G/LTE version:

      digikey.com > RF/IF and RFID > RF Transceiver Modules. Set the filter to any string with “HSPA”, “HSDPA”, “HSPA+”, or “LTE”. Sort by price, and there emerge two companies: u-blox for $26.67-$57.87 or sierra wireless for $65.66-$89.36. Looking at the datasheets, both are good choices with good published SDKs.

      mouser.com > Embedded Solutions > RF / Wireless Modules > RF Modules, then select the 4 product categories starting with “Cellular”, then they only have products starting at $98.75 that are not very interesting

      arrow.com Doesn’t seem to have any of the right product categories or products listed.

      Element14 / Farnell / Newark.com: I was able to find some products by searching for “sierra wireless”. YMMV

      This is a very important project! http://www.fsf.org/campaigns/priority-projects/

      1. I’ll look into what u-blox has on Digikey, last time I went through their website’s store, the modules they offered went for 100-200$.

        Thanks for the FSF link, I think I should contact them to see how we can help each other.

      2. You can find old 3G WWAN modules scrapped from laptops on the surplus market quite cheaply (<20$!). They come as mini-pcie cards, but fortunately using USB and not PCI-E so you can interface to it easily. If you want to make a phone make sure to get one that has the audio exposed on the connector. 4G modules are still expensive.

  2. This is so cool!! The prospect of having an ICSP , GPIO, and a not un-powerful Linux system on the go is too good to be true! Does anyone know what carriers offer 2G plans, and if they would work with this project?

    1. About the ICSP – I’m going to have an “expansion header”, I’ll make sure to include SPI and some GPIOs!

      I’m looking into incorporating a 3G modem into this. Maybe the revision I’m making right now will even have a footprint for it.

    1. They are, it’s just that the phone would need to be bigger (would be no room for a speaker), plus there are different controllers for these, as well as different breakouts (I use breakouts to make this phone easier to assemble and source parts for). I still leave them as an option – the display header accepts different breakouts, and the code should be more or less easy to adapt.

    1. So far, audio output from the Pi is the PWM way, simple and works well – but no input yet, so that you could do VoIP/record calls/scramble voice/route audio from Pi to mic. I’ll look into I2S ADCs for audio input, and maybe get an I2S ADC/DAC for communication with modem.

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