Bare bones Linux Raspberry Pi boards have already been used to build a server and a, so turning one into a smartphone couldn't be too far behind.
Pi devices don't come with standard computer elements such as a monitor and mouse, which are added on separately if needed. It's a similar story for smartphone parts such as the touchscreen and the communications module, which have to be attached independently. However, using Hunt's setup, they can be added without any soldering — so tinkerers can build a smartphone with no "fiddly electronics".
Besides the $40 Pi Model B board, the three key components Hunt used to create the "PiPhone" are a $35 Adafruit TFT touchscreen, a $48 sim900 GSM/GPRS module that allows the device to make phone calls, and a DC-DC boost converter for the battery. All up, including a LiPo battery, SIM card, a piece of foam and two cable ties, the smartphone costs $158 to make.
Hunt also developed his own interface for the device, which he hasn't released on GitHub, but he points to several other available interfaces that could do the trick.
As Hunt demonstrates, the device successfully made a call on a public mobile network and thanks to the GSM/GPRS module, it is capable of sending standard commands to hang up, send texts and transmit data.
While the device is fairly cheap to build, it still doesn't quite undercut a Nokia Lumia 520 for example.
"You'd be FAR better off going into your local phone store and picking up a normal smartphone, but hey, where's the fun in that, " Hunt says.
Though for Pi makers interested in building a smartphone, there's the added benefit of being able to disassemble the device and re-use components for other projects. In Hunt's case, he used components from a time-lapse device for photography he'd already developed for the PiPhone.
One pitfall for anyone hoping to make something a little more elegant than the PiPhone is that the setup doesn't lend itself to containment in an enclosure.
"It gets a bit warm around the CPU if you leave the unit switched on for several minutes, as there's very little air circulation. With a small fan circulating the air around it, I was able to leave it on for extended periods during development, and it was cool to the touch, " Hunt says.