#3 Parts
In the instructions it's described how to create a mobile phone keeping in mind the components described below. It's not needed to use the same ones but some parts of the setting up can change.
We have test it with Raspberry Pi 3 and Raspberry Pi Zero. The tutorials are based on Raspberry Pi 3 since it is simpler than in Raspberry Pi Zero which has some incompatibilities between the touch screen and the GSM module.
We will use the Adafruit PiTFT 2.8''. This screen can be connected directly to the Respbarry's Pi pins. It's compatible with most of the Raspberry Pi models and also let the pins free to continue using them.
The module used in the project uses a SIMCOM SIM900 chipset. There are many modules that use this chipset and in some online stores you will see several manufacturers which provides clones of this module.
The first aproach was buying some bateries in an electronic component store. It worked fine but if you want to power the battery some extra piezes are needed and that adds more complexity to the mount proces. For that reason we decided to try recycle a power bank. It's easy to desmount the piezes, not an expecific model is needed and we can use an usb wire to power the other modules. We have used one with two power output for powering the SBC and the GSM independently since the Raspberry Pi can't power the GSM itself. The other modules consume few power but the GSM will generate peaks of consume when is calling. When a peak happens the Raspberry Pi can't give enough power to the GSM, so, the module will not stablish the call or the device will reboot.
The project uses a recycled headset and microphone. We removed the plastic parts, getting only the speakers and microphone, it was not needed to cut the wires and the jack connectors can be keep to connect them directly to the GSM. In other GSMs the connection can be made with a bit of soldering but a jack connection is simpler.
We have design a simple case using 3D Builder. It is a free software from Microsoft. In the first steps we thought about it like something optional but after some time carrying the prototypes in the backpack or in a box the wirings get damaged, so, we decided to make a case. 3D builder is really easy to use, it's not suitable fot complex designs and it is so manual but it allowed us to design a simple case.
