Category Archives: Raspberry Pi

Raspberry Pi and Energy Harvesting Wireless Devices

Do-It-Yourself home automation enthusiasts will welcome the idea of a wireless arrangement when setting up devices for automating their homes. It would be still better if these sensors and switches did not require an external power source to make them work. EnOcean Pi makes both these scenarios possible, with the tiny ubiquitous single board computer, the Raspberry Pi or RBPi, acting as a home automation server.

Therefore, with the EnOcean Pi, enthusiasts can set up home automation systems without any cables connecting the self-powered sensors and switches. Depending on information from sensors measuring temperature, humidity and from those detecting human presence, the RBPi may switch lights on/off and control blinds on windows.

Enthusiasts may either have sensors and actuators communicating directly with one another, or control them through an intelligent and smart home server. The latter allows adding remote sensing and remote control for home automation, which can be done conveniently through a PC or a smart phone. This type of home server is ideally suited for a tiny single board computer such as the RBPi. The EnOcean Pi then acts as a gateway controller to the EnOcean radio world. Element14 offers three types of kits for this purpose – the starter kit ESK 300, the developer kit EDK 350 and the Sensor kit PSK 300.

The wireless module, EnOcean Pi, comes in three versions – 868MHz for Europe; 315MHz for Japan, India and North America; and 902MHz for North America. This wireless module connects to other self-powered EnOcean sensor modules, which generate their own power through energy converters that use temperature differences, light or mechanical motion as an energy source. Therefore, the RBPi receives necessary data for intelligent control from maintenance-free sensors and actuator solutions.

It is always possible for OEMs and developers to design low-cost gateways for embedded applications including smart home solutions. Rather than developing new products from scratch, developers now have the option of using the EnOcean Pi and RBPi for creating a ready-made smart home box. This can process and visualize the data coming from self-powered wireless sensors, thereafter providing central control of a wirelessly connected house.

Users wanting to develop and integrate quick applications can download the EnOcean Link Trial Version middleware that comes with the new Pi accessory. The RBPi acts as a gateway, automatically controlling the EnOcean-based energy harvesting wireless sensors, switches and thermostats. That ensures a comfortable management of lighting, shading and HVAC, thus helping to save energy.

For a bi-directional communication via radio and serial interfaces, EnOcean Pi also offers the EnOcean Smart Ack controller functionality. The RBPi can use the serial interface to send and receive radio messages transparently in both directions. In this case, using the Smart Ack technology, the EnOcean Pi acts as a postmaster and controls up to 20 bi-directional sensors.

The EnOcean Sensor Kit has a set of three wireless sensors that includes a temperature sensor, a reed switch and a push button. Rather than use a battery, the sensors have a solar cell that supplies them with power. Each sensor has a wireless module with a built-in antenna requiring no cables. That makes the sensors totally self-powered and maintenance-free.

Types of HATs suitable for the Raspberry Pi

Among several versions of the low-cost, versatile, single board computer, the credit card sized Raspberry Pi or RBPi as it is commonly called, the latest is the Model B+. Along with many new features, the RBPi Model B+ is designed to make intelligent use of expansion cards. Keeping in view of the appendage called a “hat” that many people place on their heads, the RBPi too has expansion cards known as HATs. These are Hardware Attached on Top, and they work by sitting atop the single board computer.

In reality, the RBPi is a bare-bones computer, where only the most essential peripherals are present on-board. This not only helps to keep the prices down, but also allows the primary user to start work with the SBC without being unnecessarily distracted. The primary objective for the makers of the RBPi was to let school children learn about computer programming. The RBPi achieves this objective excellently by allowing the students to start with the bare minimum requirements. They progress by using different HATs to get additional functionality. The advantage is the RBPi behaves as the revolutionary fundamental building block on which widely differing concepts can be easily proven.

Any sort of physical computing with the RBPi generally necessitates setting up extra hardware. Instead of soldering the components directly to the GPIO pins, it is prudent to add the necessary hardware in the form of an expansion card or a HAT, which you simply plug in. To use the HAT, the user has to modify the software suitably, mainly by installing the required drivers and configuring them.

The original models of the RBPi, the A and B, are really not conducive for expansion boards. The 26-pin ribbon cable connector provided on-board offer only the GPIO pins. However, several companies have made expansion boards suitable for direct plug-in to the connector, and they sit on the RBPi, making an electronic sandwich.

With introduction of the RBPi Model B+, the most noticeable change was the transformation of the GPIO connector to a 40-pin PCB header. The first 26 pins of the new header have remained identical to those on the models A and B – maintaining backwards compatibility. That allows HATs developed for the older models to be also used on the RBPi Model B+. The Model B+ has two new pins, ID_SD and ID_SC to allow connecting a serial EEPROM. That allows proper identification of the HAT and RBPi can load the necessary drivers for it. Therefore, as long as the manufacturer designs the HAT or the expansion board correctly, RBPi can configure it automatically.

The Raspberry Pi Foundation has issued specifications that all boards should follow for compatibility with the new model. According to these specifications, an expansion board can be called a HAT only if the board supports the two new pins and has an EEPROM for identification. This identification must include information about the vendor, the GPIO map and the device tree. The board must also conform to the mechanical dimensions specified and not overload the power supply of the RBPi. However, HATs need only meet the minimum specifications, which leave plenty of scope for innovation and stacking.

The Astro Pi in Space

For experiments to run in space, an Astro Pi board fitted with sensors and gadgets is a great way to begin. For this, school pupils in UK are being challenged to write apps for the tiny, inexpensive, single board computer, the Raspberry Pi or the RBPi. As Tim Peake readies for his rendezvous with the International Space Station in November 2015, the British Astronaut will carry with him two RBPis, fortified with Astro Pis. He will have six months to complete the experiments in space.

Analyzing the Astro Pi reveals it to be a HAT or Hardware Attached on Top for the RBPi. It is well packed with several goodies such as – sensors for magnetometer, accelerometer, gyroscope, temperature, barometric pressure, humidity, a real time clock with battery backup, several push-buttons and a versatile 8×8 RGB LED display. In addition, there is also a camera module and an infra-red camera on board the Astro Pi.

With all this gear, Astro Pi is most suitably equipped to carry out real-time science and innovative experiments in space. School children resident in the UK are being encouraged to join in the competition for setting up experiments that astronauts will conduct in space later this year.

The Raspberry Pi Foundation, along with the UK Space and the European Space Agency are organizing the contest. For this, they have devised five themes for stimulating the kids’ creativity and scientific thinking. These include Satellite Imaging, Data Fusion, Space Measurements, Space Radiation and Spacecraft Sensors.

Kids of ages under 11 in the primary school will devise and describe original ideas for application or experimenting on the Astro Pi. Teams presenting the two best submissions will be able to work with the Astro Pi team for interpreting their ideas. The team at the Raspberry Pi Foundation will code these two ideas and get them ready for flight on the ISS.

The competition in the secondary schools will run across three age categories of 11-13, 14-16 and 16+. A selection of the best 50 submissions will be made for each age category and they will win an RBPi and an Astro Pi on which they can code their original concept. From each age category, two winning teams will be selected.

During his six-month space stint, Tim Peake will be deploying the Astro Pis, uploading the winning experiment code, set them running, collect the generated data and download it to be distributed to the winning teams.

Astro Pi is also great for fun sciences. This is possible because of its Sense HAT, incorporating all the sensors on the single board. For example, with the on-board sensors, one can make a self-balancing attack robot that can also sense humans. In reality, most equipment for experimentation in schools is too expensive – the Astro Pi and RBPi combination changes that dimension.

Apart from the huge scope for fun sciences, useful data is expected to be gathered from using the Astro Pi sensors while on the International Space Station. Young people will have a unique chance to learn core computing skills and this will be extremely useful to them in the future.

Start Learning to Program the Arduino

Often, project builders are not sure of what they would like to build with their development boards. This happens mostly for two reasons – one, the user has just been introduced to the board and two, the user is unaware of the methods of interfacing and programming sensors, switches and other components. The second category of users is mostly those new to the world of development and in need of some hand-holding.

A Starter Shield
For these newcomers, Matt Wirth has proposed a Starter Shield for Arduino boards. With the Starter Shield, novices can learn how to interface components such as sensors for building their own interesting projects. Learning involves programming the IO headers of the micro-controller on-board the Arduino. Interestingly, users can do this without any assembly of intricate parts, soldering or wiring.

However, since many users may want to solder their own, Matt Wirth plans to release an optional kit, which will come with an assortment of components that the user will have to solder before starting. These will include potentiometers, multiple LEDs, digital and analog push buttons, temperature sensors and light sensors. To make it easy for beginners, Matt will provide lessons for programming these components, so that users can proceed with their unique creations – light meters, temperature sensor alarms, police lights and siren and many more.

An IoT Relay
For those who already have some experience in building projects with the Arduino, may find Wi-Fi and other home automation projects interesting. Of course, there are several kits available for automating homes, but most are expensive and limited in their functionality. This is where project builders can effectively use Team IoT’s IoT Relay for the Arduino board.
For those interested in home automation, IoT is a favorite subject. However, the relay solution provided by Team IoT is not limited to home automation alone. With the IoT Relay, apart from the Arduino board, users can work with any development board and create interesting project such as making automated feeders for their fish tanks.

On the IoT Relay, four outlets allow connecting to any number of devices. There is also a universal voltage control to handle inputs of 12-120VAC or 3.3-60VDC, protected with a thermal circuit breaker. That allows users to control power safely and not damage their devices. However, the IoT Relay, although inexpensive, does not come with an Arduino board and the users are expected to supply their own.

Makeblock’s mBot
For those beginning to learn to program, code and work with robots, there is nothing better than an educational robot such as Makeblock’s mBot. With STEM or the academic disciplines of Science, Technology, Engineering and Mathematics being implemented widely in schools all over the world, Makeblock’s mBot is a learning robot that helps kids with their STEM curriculum.
Featuring the mCore platform of the company, Makeblock’s mBot is based on the open-source Arduino Uno featuring a simpler wiring system. There are no GPIO pins to solder. Instead, the mCore uses RJ25 connectors, color-coded to make it easier to connect other components. Additionally, the board is compatible with Mindstorms’ Lego, other Arduino boards and shields and the Raspberry Pi.

What is a Raspberry Pi?

Raspberry Pi or RBPi, the fully functioning, tiny, single board computer costing next to nothing, has been a runaway success. However, a perennial question doing the rounds is – why would anyone want one when there is such a glut of PCs, tablets and smartphones? This article discusses the answer while exploring the RBPi doing real things.

Why is the RBPi Special?
Being an ARM-based single board computer, the RBPi, though unexceptional, is not particularly powerful. However, it is amazingly cheap and that makes it an almost disposable computer.

Several low-cost embedded systems platforms such as the Arduino are available on the market. However, unlike others, the RBPi is a complete general-purpose computer. For a very low cost, the RBPi offers the complete package of a Linux-based machine that challenges the computing power of a desktop machine of a few years ago. Apart from using it as a desktop personal machine, you can also use the RBPi as a server, a dedicated device running in kiosk mode, or for physical computing – its digital IO pins control other hardware.

The RBPi is cheap enough for one to use it to do a single job. To be equally multipurpose, other platforms would need machines that are more expensive. For example, a single RBPi can work equally well as a wall clock, a weather station, a digital photo frame, etc. Earlier, one would be using multiple temperature sensors and running long cables to a single data-collecting machine. The same job can now be handled more efficiently with an RBPi in each location, individually enabled with Wi-Fi and sending their data to another RBPi acting as a central server.

Therefore, the low cost of the RBPi is changing the optimal architecture of several projects.

Types of RBPi Available

At present, all RBPi models are based on the Broadcom BCM2835 system on a chip. This is actually a combination of a version 6 ARM architecture CPU and a VideoCore IV GPU. That makes it roughly as powerful as a 300MHz Pentium II processor typically used in the year 1999. The actual distinction between the different models is primarily based on the amount of RAM and the interfaces offered. All modes come with an HDMI and an audio port.

The initial Model A started with 256MB, while the later Models B and B+ have 512MB each. However, Linux and most applications for Linux are not as memory hungry as Windows, so the RBPi & Linux constitutes an efficient and economical combination.

Although RBPi operates on a capable Linux operating system, there are no hard disk drives and no disk interfaces either. Instead, the RBPi relies on an SD card interface that supplies the 8-32GB Operating System and file system storage.

While the Model A started with a single USB port interface, the Model B comes with a 100MHz network port and two USB ports. The latest Model B+ has one 100MHz network port and four USB ports. Therefore, you can connect a mouse and a keyboard to the Model B+ and still have two more USB ports left for connecting other appliances.

Focus Stacking with the Raspberry Pi

If you are into photography, a flatbed scanner and the popular single board computer, the Raspberry Pi or RBPi, can help you to focus stacking images in macro photography. After re-purposing an old flatbed scanner, David Hunt is using it as a macro-rail controlled by the SBC, RBPi.

Those who shoot macro photography are aware of the common issue of depth of focus limitation that shows up as the depth of field limitation in the photograph. Depending on the magnification you are trying to achieve and the camera settings, the depth of focus can be as small as 0.5mm. One solution is to stack together several images of a subject, with each image focusing on a different part of the object.

To do this with commercial solutions may set you back by as much as $600. The difficulty lies in moving the camera closer to the subject in extremely small increments, but with great accuracy. The sharp parts of the images are combined together using free software such as CombineZM, resulting in a completely sharp image of the subject right from front to back.

David Hunt decided to solve the problem with an old flatbed scanner that was lying in his attic gathering dust. Capable of 2400 dpi, the scanner had not been used for over a couple of years.

Even the drivers available for it worked only on Windows XP. Although accurate enough, David was doubtful if the machine would be capable of moving a 3Kg camera and lens combination. He decided to use the stepper motor and drive the scan element in very small increments, with the camera attached to it – it would be ideal for macro photography.

Scanners typically come with a nice flat platform on which a camera can be placed. Driving the platform forward and back requires a stepper motor that has its own drive electronics and has to be driven externally. The drive is slow, so it will let the camera remain steady while it moves. A camera with a shutter release mechanism will be useful, as you will have to take a number of snaps.

H-bridge stepper motor drives are efficient and easy to use. David used a drive capable of handling 2 DC motors or 1 stepper motor with two coils. For powering the motors and the drive, David used 3x AA type batteries. Therefore, he was able to connect four GPIO pins from the RBPi to control the drive and the motor. However, driving the motor through opto-couplers would have provided more safety for the RBPi.

The binary sequence of 1000, 0100, 0010 and 0001, when repeated, will drive the motor forward one-step at a time. The same sequence, repeated in reverse, will allow the motor to move back one-step at a time. David programmed the RBPi to generate these sequences repeatedly while he added an additional circuit for releasing the camera shutter between each movement of the platform.

With the above contraption, David can move his camera forward towards the subject in the smallest increments of 0.02mm, and take images at each increment.

ArdHat for Connecting Raspberry Pi to the Real World

Many users of the tiny, inexpensive, Linux-based single board computer, the Raspberry Pi or RBPi, would like to connect it to the outside world, but do not know how. According to Maker Jonathan Peace, ArdHat is most suitable for connecting the barebones Unix platform to the real world. Therefore, he calls it the “missing link that connects the Raspberry Pi with the real world.”

Onboard the ArdHat is an Arduino-compatible embedded MCU, the ATmega328P. Its specialty is very quick response to all real-time events, allowing the RBPi to take care of the rest of the heavy lifting. HATs or Hardware Attached on Tops are most suitable for the RBPi Model B+. These HATs conform to specified standards and make life easier for users. One significant feature of HATs is an onboard system to allow the RBPi B+ identify the connected HAT and automatically configure its GPIOs and drivers for the plugged-in board.

Real-world systems need low-power operation, real-time performance and environmental protection and awareness, all of which the ArdHat provides. As a super-compact RBPi compatible HAT, the ArdHat enhances and protects the RBPi for applications in the real world, while being accessible to everyone possessing an Arduino.

You can have the ArdHat in four different models – two with long-range radio modules and the other two without the radio. All four are packed with analog sensors, user interface controls, a real-time clock, 5V Arduino shield capability, supply monitoring, a wide operating range of voltages that includes automotive, full power/sleep management and high current outputs for driving peripherals. All these are accessible from the AVR chip on-board the ArdHat or the RBPi.

Those looking for more power can also choose between the ArdHat-W and the ArdHat-I. The first has a 15Km long-range ISM wireless node, while the latter has a 10-DOF inertial measurement unit. Both make the boards ready for IoT right out of the box.

Apart from a flat top design that allows plenty of space for placing a battery or a prototyping board, the ArdHats accept several Arduino shields. Users can also buy an optional high-capacity 1800mAh battery, especially tailored to plug-in directly into the JST standard connector. The whole arrangement fits snugly between the shield headers of the board’s flat top design.

Among the smart power management feature of the ArdHat is a power switch and charge control. That allows the RBPi to run on several types of power supplies, including LiPo batteries to automotive supplies. Therefore, the HAT can simply connect to systems operating on 5V and drive them – smart LEDs, quadcopters and servos.

Other than protecting the RBPi from external power outages and voltage spikes, the TopHat enclosure offers a physical safeguard as well. Made of laser-cut Perspex, the enclosure allows access to pins of the Arduino shield for teaching and experimental purposes. At the same time, the enclosure protects the delicate circuitry of the RBPi circuit board.

The scheduler and applications for the ArdHat are entirely open-source. Using the Arduino IDE, users can modify and update even the preloaded sketch of the real-time software on the ArdHat.

An Explorer HAT Pro for the Raspberry Pi

If you are looking for a HAT or Hardware Attatched on Top for your Raspberry Pi (RBPi) that has motor and touchscreen drivers, integrated sensors and interfaces with 5V devices, the Explorer HAT is for you. Standard add-on board HATs allow the Linux-ready SBC, the RBPi, to configure its GPIO signals and drivers to control and use external devices.

Pimoroni has two models of HATs for the RBPi – the Explorer HAT and the Explorer HAT Pro. They support the HAT standard set by the Raspberry Pi Foundation, matching requirements for the RBPi 2 Model B, including the first-generation Model B+ and Model A+ boards as well.

To integrate inputs from 5V Trinkets or Arduino boards, the Explorer HAT offers four buffered 5V inputs. In addition, four powered 5V outputs on the board can supply 500mA to drive stepper motors, relays and or solenoids. The Explorer HAT also has a mini-breadboard, four capacitive touchpads, four LEDs and four capacitive alligator clips.

In addition to all the above features of the Explorer HAT, the Explorer HAT Pro has analog inputs and two motor drivers in H-bridge configuration to drive micro-metal geared motors and similar. The Explorer HAT Pro also comes with plenty of 3v3 features from the GPIO. However, these are unprotected.

According to the specifications defined for the Explorer HAT, each board has four inputs each 5V tolerant including 5-channel buffers with 2-5V support. There are four 5V powered Darlington-array outputs capable of 500mA per channel, limited to 1A total. The front edge of the board has four capacitive touch pads along with four LEDs, controlled independently. Including the mini-breadboard, the dimensions of the Explorer HAT are 65x56x13mm.

The Explorer HAT Pro version adds four analog inputs including two bi-directional motor drive outputs of the H-bridge type capable of handling 200mA per channel. It supports soft-PWM for full speed control. Additionally, there are the unprotected 3V3 GPIO features.

Compared to the Pibrella, another board made by Pimoroni, both the Explorer HAT and the Explorer HAT Pro share many similarities, but also add a lot more besides. For example, the analog and digital inputs are a great help, especially since you can connect inexpensive and simple sensors such as the TMP36, while taking advantage of the built-in ADC.

The capacitive touch buttons of the Explorer HAT not only allow interfacing with connected components, but also allow independent working. For example, you can send a tweet, an email or a text message by simply tapping one of the buttons. There are many other possibilities with these capacitive touch buttons. You can connect crocodile clips and brass contacts for using fruits as buttons. Of course, the software will have to be tweaked somewhat to get the proper sensitivity.

Plugging HATs on the RBPi invariably causes loss of access to some GPIO pins. The Explorer HAT breaks out the most useful pins from the GPIO, making them easily accessible. Pimoroni provides intuitive Python libraries and a built-in tutorial for all to use.
Overall, both the Explorer HAT boards are a great value for money not only for kids playing and learning to interface with the RBPi, but also for grown-ups.

Energy Monitoring with the Raspberry Pi

If you are looking for an all-in-one device for monitoring your home energy needs, a low-cost single board computer such as the RBPi or Raspberry Pi along with an add-on shield is all you need. The emonPi board is a low-cost shield that is bereft of any enclosure, HDD and LCD.

However, when connected with an LCD for status display, hard-drive for local logging and backup and a web-connected RBPi, the emonPi makes a high-quality and robust unit. Enclose it in a suitable enclosure and you have a stand-alone energy monitoring station.

The design of the emonPi allows it to be a perfect fit for those who install heat-pump monitoring systems. Usually, these systems require several temperature sensors that must also be wired up along with power monitoring. Accompanying modules offer a myriad of options.

For example, the emonPi can also act as an emonBase, as it has options for radio (RFM12B/RFM69CW) to receive data from other wireless nodes. These nodes include emonTH, for measuring room temperature and humidity. Another energy-monitoring node, the emonTX V3 can send the current time to the LCD, emonGLCD.

The status LCD makes it easy to install, setup and debug the emonPi system as an energy monitor sensing mode and an all-in-one remote posting base station. This makes the emonPi a great tool for remote administration, since, with a proper networking configuration the RBPi can be accessed remotely. Thus, you may check its log files and even upload firmware onto the ATmega328 of the emonPi.

The emonPi monitors energy through a two-channel CT or current transformer along with an AC sample input. It can power up the RBPi and an external hard disk drive without using an external USB hub. Additionally, the emonPi can function even without a hard disk drive being connected to it.

The RJ45 breakout board makes it very easy to attach several temperature sensors to the RJ45 on-wire temperature bus provided by a DS18B20. This is eminently suitable for multi-sensor setups such as in heat pump monitoring applications. The RJ45 also has IRW and PWM I/Os.

The emonPi is compatible to all models of the RBPi and its options for RFM21B and RFM69CW along with an SMA antenna makes it capable of receiving or transmitting data from other sensor nodes. One can control remote plugs with the OOK or On-Off keying transmitter.

All hardware, firmware and software are open-source and the ATmega328 on the emonPi can remotely upload sketches via the serial port of the RBPi. However, compared to the emonTX V3, emonPi has some disadvantages.

The emonPi module is not capable of making measurements on three-phase systems as there is only one CT monitoring two channels. As the RBPi has high power requirements, it is not possible to power the emonPi from batteries. You cannot also use an AC-AC adapter, because, for measuring real power, you must use both a 5VDC and a 9VAC adapter. Remote location of the utility meter requires Ethernet connection or Wi-Fi connectivity. Additionally, the emonPi requires a larger enclosure as compared to what an emonTX V3 uses.

Slow Scan Television Camera with the Raspberry Pi

Ham radio operators use their radio equipment and computers to send and receive pictures over wireless. Earlier, most images sent through voice transceivers were low resolution black and white. However, with improvement in technology, nearly all images are of higher resolution and in color. The technique for sending and receiving pictures over radio is called Slow Scan TV. All that is required is a VHF scanner, a computer and a camera. This project replaces the computer with a Raspberry Pi or RBPi, the tiny credit card sized single board computer.

The RBPi with the PiCam forms a wireless camera for transmitting images over very long distances such as tens of kilometers. Finally, the images will be transmitted by ham or amateur radio equipment that uses slow scan television or SSTV over the 2m band (144.5MHz). Here, the RBPi is capable of generating the HF FM signals, and no additional electronics is needed for transmissions at low power. However, with a low pass filter and a single or a two-transistor amplifier, a more powerful transmission can be achieved.

Greater distance coverage is the main advantage of using SSTV over Wi-Fi for transmitting pictures. Using the RBPi as a wireless security camera, you can transmit pictures to distances far beyond the range normally covered by Wi-Fi networks. One of the main requirements is you will need a ham-radio license for using this application.

For transmitting a picture, you will first need to capture it using the PiCam. The program that RBPi uses to do this is named as rapistill. Once the image is captured, it has to be converted to a SSTV sound file. Although there is a program called PySSTV, the conversion rate is very slow and it may take several minutes for converting a single image. However, a simple program implemented in C – PiFm – works very well. The program allows setting the audio sample rate from the command line and converts the picture to an SSTV sound file in just under four seconds.

Although it is customary to transmit the sound file over a radio transmitter, it is much more fun to allow the RBPi to generate its own high frequency signal. Following the Wiki of the Imperial College Robotics, you can turn your RBPi into an FM transmitter. Their code used DMA, but the bandwidth used is very high and the timing for SSTV is not accurate.

In PiFm, bandwidth reduction is very simple. Usually, for FM, the bandwidth is set with the modulation index. This index is the volume of the audio signal modulating the HF carrier. Timing is very essential for SSTV, as a small change in the sampling rate results in slanted images. The timing correction, in the form of a constant, can be set from the command line.

Another requirement when using ham radio for transmitting SSTV signals is that you are required to transmit your call sign in every transmission. This information has to be added to the picture and the RBPi uses imagick from the python image library to accomplish this. Whenever something interesting happens in front of the camera, the RBPi captures the image and sends it over wireless.