The Raspberry Pi is particularly popular as a gateway and control computer in semi-industrial environments. Sfera Labs(http://www.sferalabs.cc) has specialized in the field of control applications and has already launched two product families with CPU and I/O devices on the market in recent years (Fig. 1). The products of the "Strato" family form the CPU segment and are aimed at computing-intensive edge applications. Inside is a Raspberry Pi board as used in the consumer segment or a compute module. The "Iono" family comprises the I/O modules, which are equipped with either Arduino boards or the Raspberry Pi in credit card format. All these devices are housed in a top-hat rail housing. A new addition is the Iono Pi Max (image), which combines both - a Raspberry Pi compute module and a large number of I/Os. This means that functions that were previously spread across several devices are now combined in one device. Sfera Labs' strategy is not to use any proprietary parts, which is why only standard boards or modules from Arduino or Raspberry Pi are used.

The housing of the Iono Pi Max features the Ethernet and USB connections of the Raspberry Pi compute module, an RJ12 socket that carries the I2C interface and screw terminals with industrial I/Os. These inputs/outputs include relays, digital I/Os (bidirectional TTL I/Os, digital inputs and open collector outputs), CAN, RS-232 and RS-485 interfaces, dedicated inputs for temperature sensors and a Wiegand interface. The latter is widely used as a connection for card readers on door access systems.

Numerous extras

In addition, the Iono Pi Max has a whole range of special features that allow it to be adapted to many areas of application. These include a Microchip/Atmel SAME54P20 microcontroller, which controls the inputs/outputs and much more. The microcontroller, which works with a Cortex M4 core, configures the I/Os and determines whether the serial interfaces work in RS-232 or RS-485 mode, whether simple CAN or CAN-FD is used.

Another special feature are two micro SD slots. Although the Raspberry Pi Compute Module can manage two SD cards, it can only boot from one of them. The M4 microcontroller uses a switching matrix to ensure that the card slots can be swapped so that booting from both SD cards is possible. This enables safe firmware updates in the field. If something goes wrong when starting with the new firmware, you can simply switch back to the old version by switching and rebooting.

Another extra: an external battery can be used to provide an uninterruptible power supply for the device. Until now, this has only been possible with 12 or 24-volt lead-acid batteries. However, Sfera Labs promises that other battery types will also be possible with future firmware updates. The internal charging circuit supplies the battery with 600 mA. For less power-hungry applications, Sfera Labs recommends a 1.2 Ah battery, which is sufficient to keep the device running for a few minutes for an orderly shutdown. A 7 Ah battery is recommended for power-hungry applications.

Also on board: a secure element from Microchip (ATECC608A), which is connected to the compute module via the I2C bus. This element secures the boot process and stores up to 16 keys or certificates. Sfera Labs products are sold directly via its own website sferalabs.cc or via Mouser.