Figure 1: Pi-Phone
Out of all the projects based on Raspberry Pi, it is one of the most interesting projects. It uses an Adafruit touchscreen display screen along with a Sim900 GPRS/GSM module in order to make calls. This project is a way to to help viewers see what best can be done with very small components. The hardware for this phone is quite similar to the Raspberry Pi based time-lapse controller, but a few steps ahead in some aspects. This one, for example, uses a SIM900GSM module that has a connection with the Raspberry Pi through UART. It also contains a LiPo battery that will fit nicely between Raspberry Pi and TFT screen. This allows it to stand alone without any hassle of wires hanging from here and there.
Figure 2: Components of PiPhone
The Sim900 GSM/GPRS module in it permits the owner to send AT commands to the phone for making calls, hanging up, sending data, texting, and so on. If you see the below given picture of complete module you will see the sim placed on the bottom of the unit, this permits the module to stay connected with the GSM network. Below the GSM module, there is an off-on switch along with a DC-Dc converter that can easily convert 3.7 volts from its LiPoly battery into 5volts that is used by everything else.
Figure 3: LiPo battery
In the next image you can see the side view of the phone along with the LiPo battery. The battery comes from Adafruit that is nicely fitted between Pi and TFT. The only challenge associated with this set up is heat. It starts generating heat near the CPU as the air circulation is very less. So, while you are developing one such unit make sure you keep it under a fan or in a well-ventilated environment so that you can leave it open for longer periods. The 6 pin header of the GSM module might stick out a little, it is better to de-solder it and then solder the wires directly in the PCB.
Figure 4: Dispalys separation between GSM module and foam-core board
The other side view of this phone shows the separation between GSM module and foam-core board from the Raspberry Pi system. You can always use some cable-ties in order to hold everything together in a neat manner. The total cost of this phone doesn’t cross $158 which is a bit ahead of local smartphones. But it is fun to make it, isn’t it?
Filed Under: Reviews