With over 12 million units sold, the Raspberry Pi single-board computer is the third best-selling computer in the world. It is now not only used by hobbyists in the maker scene, but also increasingly in the industrial environment. More and more developers are using systems based on the open source mini-computer for prototypes and evaluations. This is often done initially without a professional housing and with a supply voltage via a standard 5V USB power supply unit. In these cases, the required interfaces and additional functions are implemented with various Pi Hat plug-in modules. This often solves the task at hand, but the setup is in no way suitable for 24/7 productive operation. One example: USB power supply units are often too weakly dimensioned, resulting in subsequent errors such as corrupt µSD cards due to the unreliable power supply.

For reliable operation, companies could fall back on classic panel PC and control systems, but are often not prepared to pay the price of classic industrial products. After all, the areas of application are often very limited and the prototype runs so well that a costly porting to another system is avoided. In addition, users tend not to focus on use in extended temperature ranges and high long-term availability for these applications. More important is the software compatibility with the Raspberry Pi ecosystem and the associated availability of a large number of software libraries, application programs and documentation in the open source sector.

Bluetooth and WLAN connection

Janz Tec developed the emPC-A/RPI3 embedded PC based on the mini computer in response to numerous customer inquiries.

The block diagram of the base board of the emPC-A/RPI3 embedded PC.

© Janz Tec

The current generations with the Raspberry Pi 3 Model B are CE-compliant and have Bluetooth and Wi-Fi connectivity. These two wireless interfaces open up completely new fields of application, particularly in the IoT environment, for example for connecting Bluetooth-based wireless sensors.

However, another area of interest for many users is the combination with an integrated display with touch operation. This is why Janz Tec developed the emView-7/RPI3 panel PC. By using the Raspberry Pi 3 Model B in combination with the official Raspberry Pi display, this offers a cost-effective and fast entry into the realization of industrial HMI applications that support multi-touch. The display offers a resolution of 800 × 480 pixels and capacitive multi-touch functionality. The device is the latest member of the emView Panel PC family from Janz Tec and represents the entry-level model in this series.

100 % compatible

The emView-7/RPI3 panel PC is equipped with connections for supply voltage, I/O, CAN bus, RS232/RS485, network, USB and serial console.

© Janz Tec

The emView-7/RPI3 has the same interfaces as the emPC-A/RPI3 embedded PC. It is 100% compatible with the freely available standard Raspberry Pi operating systems: Linux distribution Raspbian and Microsoft Windows 10 IoT Core. A key feature is the base board developed by Janz Tec, which ensures a stable 5V power supply for the module. The input voltage range is 9 to 32 V and is therefore ideal for 24 and 12 V operation. The supply voltage and the industrial interfaces CAN bus, serial interface RS232/RS485 and the four digital inputs and outputs are implemented on a common 24-pin I/O socket. A serial console is provided via a D-Sub socket so that debugging and maintenance work can be carried out via a terminal connection. The operating temperature range between 0 and +45 °C is a little more limited than with some other industrial Raspberry Pi-based products, but Janz Tec's focus is on the most reliable continuous operation of the system possible, taking into account the limitations of the module.

Even during the development of the base board, the focus was on future software compatibility with mainline Linux drivers. For this reason, electronic components were selected for the industrial interfaces that can also be found on other Hat expansion boards. The microchip MCP2515 CAN controller controls the galvanically isolated CAN bus connection and an NXP SC16IS740 UART provides the serial interface, which can be switched between RS232 and RS485. The interfaces are addressed via standard Linux techniques, such as the SocketCAN library for the CAN bus and the Linux device name /dev/ttySC0 for the serial interface. The four digital inputs and outputs and the two user LEDs are connected internally to the GPIO connections. This provides a large number of freely available libraries and applications for programming and controlling them.

Why not the compute module?

Software compatibility was also one of the deciding factors for using the standard Raspberry Pi 3 Model B module instead of the equally popular compute modules. Even though these modules allow greater integration and more compact designs, the software support here is not as comprehensive as for the standard variants. In addition, popular features such as WLAN and Bluetooth would not have been as easy to implement.

One of the most frequently used extensions is the RTC board. It provides the real-time clock not included with the module. On the emView-7/RPI3 base board, the battery-buffered real-time clock is realized with the Microchip MCP7940N. The CR2032 button cell used provides the clock with the necessary energy for many years.

Many tests have shown that the reliability of the system depends not only on the power supply but also to a large extent on the quality of the µSD card used. This must be designed for use in industrial environments; normal consumer µSD cards often fail after a short time. As a result, they are either no longer readable or show serious data loss. The type of µSD card used must also be able to withstand the power supply being switched off several thousand times without the operating system having to be shut down first. The emView-7/RPI3 is equipped ex works with a corresponding µSD card from a specialized brand manufacturer.

The installation of additional software is often very complicated for systems from the embedded environment. Missing functions must first be requested and purchased from commercial providers or at least compiled at great expense for the respective hardware platform using a C/C++ toolchain.

Flexibility in the software

With emView-7/RPI3, users with Linux as the operating system and the Raspbian Linux distribution can install freely available open source projects using the included package manager. If, for example, the function of an MQTT broker is required on the system, users can install the necessary package by calling 'apt-get install mosquitto'.

The flexibility starts with the selection of the desired Linux distribution. If, for example, the standard Raspbian distribution from the Raspberry Pi website is to be used instead of the specially adapted and preconfigured distribution supplied by Janz Tec, users can simply install the drivers for the CAN bus, serial interface and RTC. As not every user has knowledge of Linux driver development and compilation, Janz Tec has published a driver installation script on GitHub (https://github.com/janztec/empc-arpi-linux-drivers). This automatically downloads the Linux kernel source code for the currently installed kernel version and compiles and installs the drivers as kernel modules. Standard settings for Linux configuration files can also be made automatically, for example the CAN bus is preset to a data rate of 500 kbit/s and the green LED is configured as a µSD activity indicator. The script is available in source code, so that the settings made can be traced exactly and can therefore also be customized.
The Raspberry Pi presents hardly any entry barriers to developing your own software. Depending on the level of knowledge and preferences of the software developer, various programming languages can be used, ranging from simple graphical programming languages - such as Scratch, Perl or Python - to classic high-level languages such as C, C++ and Java.

A number of instructions and software libraries from the maker environment that are freely available on the Internet are already so mature thanks to the large community of users that they often run smoothly in industrial use. For example, the projects for accessing GPIOs (http://wiringpi.com/), serial interfaces (http://elinux.org/Serial_port_programming) and the CAN bus are very interesting (http://public.pengutronix.de/software/libsocketcan/).

The use of free software can potentially save a lot of time and money in the development of your own application, so that more resources can be invested in improving your own products. The associated reduction in time-to-market is a further advantage. On the other hand, Linux also represents a hurdle for many companies with its diverse license conditions, which can differ from software package to software package. The risk of unintentional license violations often stands in the way of using Linux outside of prototypes. The standard distribution supplied by Janz Tec is therefore based on Raspbian Lite. It only contains software packages that are available under free software licenses and can therefore also be used in a professional environment.

The alternatives

If the customer has more demanding requirements in terms of the ambient temperature range or long-term availability, it may be advisable not to use a Raspberry Pi-based solution and instead choose the other industrial and panel PC solutions from the emPC and emView series, which have been tried and tested for years.

On the hardware side, other systems are in the same performance class as the Raspberry Pi, but have a modular design and can be expanded with additional interfaces. If required, the classic industrial computers have an elaborate passive cooling solution for reliable operation at ambient temperatures of -40 to +60 °C.

On the software side, the necessary adaptations when switching from Raspberry Pi-based systems to another system in the emPC series, for example the emPC-A/iMX6, are also very straightforward. Raspbian on the Raspberry Pi and Debian on the emPC-A/iMX6 differ only in details and for many applications the same packages can be installed via the respective package manager. If, for example, a C/C++ toolchain for ARM is used for software development, it is easily comparable on both systems because the same ARM HardFloat compiler can be used. Individual consultation with customers depending on the application area is important here in order to clarify when it makes sense to switch to alternative emPCs or emViews.

Shorter development times

Until now, the development cycles for hardware and software in the industrial environment have been rather lengthy. If you also consider the time that an application has been in productive operation, it used to take five to ten years or more. With the entry of 'professional makers' into this professional field, there is a growing desire for shorter, more agile development cycles and the use of increasingly up-to-date technology. To assess the opportunities and risks of this trend, industrial applications can now be realized and tested in use with the Raspberry Pi-based systems using the many freely available software libraries, programming languages and instructions. This is a simple way for anyone to assess for themselves whether the change will lead to reliable solutions and products and for which areas of application they are suitable.

Author: André Massow is a software developer at Janz Tec.