Raspberry Pi 3, now in Compute Module format

New Products | January 16, 2017

By Graham Prophet

Distributor RS Components (RS) and Allied Electronics, (Electrocomponents) are building the Raspberry Pi Compute Module 3 (CM3) based based on the Raspberry Pi 3 architecture. Designed for professional engineers to develop embedded systems, the new Raspberry Pi 3 Compute Module (CM3) fits into a standard DDR2 SODIMM socket and provides the same basic processing capabilities as the Raspberry Pi 3.

RS’ Rob Maycroft, product manager for Raspberry Pi, comments on the continuing “huge” growth of the Pi product line, and relates it to the wider trend to ope-source software, plus off-the-shelf hardware; “80% of new embedded designs [in the immediate future] will start with a modular board-level product.”

In common with the Raspberry Pi 3, CM3 incorporates a 64-bit Broadcom BCM2837 application processor, built around an ARM Cortex-A53 quad-core processor running at up to 1.2 GHz, and 1 GB of LPDDR2 RAM. It provides 4 GB of on-board eMMC Flash storage, and retains an identical pin-out to the original Compute Module (CM1). It has almost the same profile, with an identical footprint that is 1 mm deeper (thicker) than the original CM.

Raspberry Pi founder Eben Upton remarks that the CM3 has been in development since the ‘Pi 3’ was introduced early in 2016; in common with the upgrade that the Pi 3 represented, it has around 10x more processing power than the original CM. Upton earlier said of the Pi 3 that it took the board into being a “real computer” – in contrast to its orginal STEM aspirations, and same shift in capability is true of the CM3.

RS and Allied are stocking the new low-cost Raspberry Pi 3 Compute Module Lite (CM3L). This includes the BCM2837 application processor and 1 GB RAM, but has no on-board Flash storage. Developers can provide an eMMC device or SD card socket on their application-specific base board. Upton adds that there is considerable demand for the non-flash version from industrial users. The Lite version trims $5 from the $30 cost of the CM3.

With the intention to penetrate the industrial design sector, and asked if the intellectual property in the CM3 might be available to license, Upton commented that it would not be ruled out, however, “People tend to underestimate the benefits to be had from the modular approach,” referring to the detail design work and many iterations that have gone into optimising the layout, performance and manufacturability of the module. “In a real cost/benefit analysis, [the switch from module to integrating the IP] would be at a much higher volume point than many people would expect. Even if you take the Gerber files etc. there is still a lot of complexity… in the SO-DIMM module, a lot of the high-tech part is taken care of.” Running a full workload with all cores loaded, the CM3 can consume up to 4W, Upton says, adding that it is not intended for tasks that need ultra-low-power in shutdown, powering down to the 100 mW-region. It has not been submitted to formal industrial/environmental certification testing, but Upton says that the CM has proved “surprisingly capable” in this respect.

Like its predecessor, the Raspberry Pi 3 Compute Module is designed for integration into industrial-type applications. One example is the range of next-generation large-format displays from NEC. These integrate a socket for an optional Raspberry Pi 3 Compute Module, and are designed for use in brightly lit public spaces such as schools, offices, shops and railway stations.

The Raspberry Pi 3 Compute Module can also be obtained from RS and Allied as part of a development kit, bundled together with the Compute Module IO Board. This simple, open-source, development board brings out all of the IO connectivity of CM1, CM3 or CM3L to pin headers and flexi connectors, and allows the developer to program on-board eMMC Flash over USB. It serves as a prototyping platform, and as a starting point for the development of application-specific base boards. PCB layout design files for the baseboard routing (for example for the Allegro package) are available.

Upton anticipates that “most” users will run the standard Debian-based (Linux) image offered by Raspberry Pi. “We have not seen much use of RTOS [in the space addressed by the CM] – you have to really need the real-time attributes to justify the added complexity of an RTOS.” The module does not come pre-flashed, although RS indicates that if a volume user requested it, the option would be explored.

“The introduction of this new version Compute Module shows strong commitment from the Raspberry Pi Foundation to the industrial arena, moving beyond the platform’s original mission as an educational programming tool,” concludes Rob Maycroft, at RS.

RS; https://uk.rs-online.com/web/generalDisplay.html?id=raspberrypi

Raspberry Pi Foundation; www.raspberrypi.org