The PiTalk from SB Components is a 3G enabled board that can be used to implement a modular mobile solution for Raspberry Pi. It is compatible with most models of Raspberry Pi, including Pi Zero, Zero W, Pi A+, Pi 2 and Pi 3 B/B+.
PiTalk is based around a Quectel UC15 UMTS (Universal Mobile Telecommunications System)/HSDPA (High-Speed Downlink Packet Access) module. Put simply, this means that it can be used for 3G communication to make voice calls, send/receive SMS messages or provide data communications when no WiFi is available.
As with most Raspberry Pi add-on boards, setting up the PiTalk is simply a matter of mounting the board onto the GPIO header of the Pi. The PiTalk is supplied with 3 16mm male-female standoffs with matching screws and nuts. These can be used to secure 3 corners of the PiTalk to the Pi. One corner of the PiTalk board has a 3.5mm jack socket on one side and components on the underside, so is unable to accept a standoff. PiTalk is supplied with a small SMA antenna which must be screwed onto the antenna socket on the side of the PiTalk board.
Although Pi add-on boards are typically mounted on the GPIO header, the PiTalk can, as an alternative, be connected to the Raspberry Pi using a micro USB cable. If connected in this way, the PiTalk will need to be powered using a separate power supply through a second micro USB connector.
For 3G communication, the PiTalk requires a SIM card to be inserted into a sprung micro-SIM slot on the underside of the board.
The software for PiTalk can be installed from GitHub. The PiTalk is designed to run on a 3.2″, 4″ or 5″ screen, and there is a separate repository for each use case.
To install the required software, the appropriate repository should first be cloned to the Raspberry Pi. Following this, running the setup script will install any additional software dependencies. The GitHub page provides full details of how to install and run the PiTalk software.
Adapting The Software
The supplied software for the PiTalk is Python based. As such, it is relatively simple to adapt the code or write new code for a specific application requirement. In some cases we did find that the vendor software did not quite function as expected, so did require some modification to make it do what was required. Despite this, the software provided does offer an excellent basis for developing other applications for a particular user requirement.
Mobile Module Switch
One minor irritation with the PiTalk is that the mobile module does not power up automatically when power is supplied to the PiTalk board. In order to power up the mobile module, it is necessary to physically press a tactile button that is mounted on the PiTalk board. As far as we can tell, therefore, it is not possible to power the mobile module up or down by means of software.
Having said that, however, from an examination of the circuit board, it would appear that it might be possible to wire up one of the extended GPIO pins, via a resistor, to one of the terminals of the tactile switch. The GPIO pin would then need to be programmed as normally high (+3v), and to send a brief low (0v) pulse to switch the mobile module on or off.
Note – We have not tried re-wiring the PiTalk in this way, so can not confirm (or recommend) this as a practical solution to providing software switching for the mobile module.
Using the PiTalk
Although the PiTalk is designed to work with a small (3.2″, 4″ or 5″) touchscreen, we did all our testing using a standard HDMI monitor. For our testing of the PiTalk, we used the supplied software; though, as mentioned previously, we did need to fix a couple of minor bugs to get the code to work as required.
We were fortunate enough to have access to a PiRelay board, so could try out the supplied ‘Home Automation’ example project. This example application allows the 4 relays on the PiRelay board to be switched on or off by sending SMS messages to the PiTalk. The PiTalk sends a response SMS confirming the action.
Despite the few minor issues we found with the software, the PiTalk delivers an excellent platform for all manner of IoT type applications. Since it works seamlessly with the Raspberry Pi, it can easily be adapted to work with additional hardware such as a Pi Camera, sensors and other HATs. The PiTalk board itself has the provision to connect an external microphone and speaker or to connect a headset via a 3.5mm jack socket. There are also headers for 2 ADC channels for connecting external analogue sensors.
The versatility of Raspberry Pi means that the PiTalk board could be used in applications such as home security or home automation, robotics, remote monitoring, SMS control, and probably countless others.