[Updated: Aug. 19] — Rhombus Tech’s Allwinner A20 based, “fully libre” EOMA68 COM and carrier boards can be installed in 3D printed mini-PC or laptop cases.
For the past five years, UK-based Rhombus Tech, led by developer Luke Kenneth Casson Leighton, has been developing a fully open source, removable computer-on-module (COM) in a standardized format known as “EOMA68.” Rhombus has now gone to CrowdSupply to help fund an “EOMA68-A20” module based on Allwinner’s A20 SoC, as well as a mini-PC and a 15.6-inch laptop built around the COM.
The EOMA68 (Embedded Open Modular Standard 68) form-factor is based on the old PCMCIA form-factor, which has a 68-pin interface. Modules built to the standard can easily be moved from one device to another, including among multiple categories of devices. Don’t worry about slipping them into normal PCMCIA slots, though, since the EOMA68 spec wisely defined a slightly larger-than-PCMCIA outer shell dimension to prevent mishaps.
EOMA68 module from two angles
(click images to enlarge)
The developers of the EOMA68 standard made a point of defining its signal interface in a manner that would give the modules longevity. Quoting from the spec…
Re-purposing of the PCMCIA interface and form-factor has been chosen to create portable mass-volume (100 million units and above) Embedded Computing Modules (Computer on Module). Mass-volume “Lowest Common Denominator” interfaces have been chosen, all of which have existed for over a decade, but are low-power enough to be standard across virtually all mass-produced powerful Embedded CPUs.
As a result of this EOMA68 module standardization, the two “EOMA68 Computing Devices” in Rhombus’s A20-based EOMA68 campaign should be upgradable when more powerful EOMA68 modules become available from Rhombus or others in the future. The systems can also be constructed using 3D-printable parts, thereby reducing landfill and consumption.
PCMCIA-sized EOMA68 COMs can move from device to device
(click image to enlarge)
The EOMA68 specification explains that in contrast to EOMA68, existing COM standards, such as Qseven or various SODIMM-style modules, are “not realistically user-upgradeable (not for the average person) because products require tools, technical knowledge in the selection of technically-compatible replacement parts, and expert knowledge in the handling of electronics for ESD-precautions before even opening the case.”
Rhombus EOMA68-A20 module details
The durably encased 85 x 55mm Rhombus EOMA68-A20 module supports its dual-core, 1.2GHz Cortex-A7-based Allwinner A20 SoC with 2GB RAM and 8GB NAND flash. There is also a micro-SD slot, a micro-HDMI port, and a micro-USB OTG port with bi-directional power. The module’s other onboard interfaces, fulfilling EOMA68 specifications, are listed as follows:
- SD/MMC 4-bit with multiplexing to SD/MMC and SPI on 6x pins
- 18-pin RGB/TTL (for LCD Panels and DVI/VGA/HDMI or other display conversion ICs)
- 2x USB ports with Low/Full Speed and optional Hi Speed, 480Mbit/s (1x supports optional USB 3.0 or USB 3.1)
- 4-pin GPIO with “External Interrupt” capability for fast hardware interrupt to the SoC
- 1-pin PWM, multiplexed to GPIO
- TTL-compatible UART (Tx and Rx only) multiplexed to GPIO
- SPI up to 4-bit, multiplexed with 6x GPIO pins
Rhombus EOMA68-A20 module PCB front (left) and back
(click images to enlarge)
The EOMA68-A20 COM and systems are claimed to be scrupulously “libre” in both hardware and software, to the point where Rhombus omitted the usual Mali-400 GPU that accompanies the Allwinner A20, due to its lack of accessibility and documentation. So don’t expect much in the way of graphics.
As for software, the Parabola GNU/Linux-libre distribution that’s available preloaded on the EOMA68-A20 module is said to be so purely sourced that this version is expected to receive the Free Software Foundation’s “Respects Your Freedom” (RYF) certification before the first units ship in March 2017. Like this “Libre Tea Computer Card,” other versions equipped with Debian, Devuan, and Fedora 24 are available for $65 each.
EOMA68 enclosure options
You can extend these SBCs with a $20 breakout board that features a surface-mount PCMCIA header. There’s also a $35 pass-through card that inputs HDMI and USB signals and passes them on. The latter is said to turn a “Laptop Housing into a portable, battery-powered dock for your smartphone, USB-HDMI dongle computer, and tablet, or a second screen, keyboard, and mouse for your existing laptop or desktop PC.” There’s also a $14 USB and HDMI cable set.
Rhombus EOMA68 mini-PC baseboard prototype with EOMA68-A20 card installed, and its optional laser-cut plywood mini-PC enclosure
(click images to enlarge)
A $55, laser-cut plywood constructed Micro Desktop Housing can be used to turn the EOMA68-A20 COM into a mini-PC. The 4.5 x 4.5 x 0.5-inch case includes a user-upgradable slot for the EOMA68-A20, and adds two USB 2.0 ports, a VGA port, a 5.5mm DC jack supporting 7V to 21V, and a 20-pin internal GPIO expansion header. This gives you a full mini-PC for $120 plus any of the above add-ons you might desire.
EOM68 laptop case (left) and 3D-printable case design
(click images to enlarge)
There are three laptop kit options. You can choose a $450 Print-It-Yourself package, which gives you parts including cabling, boards (main, power, and controller, assembled and tested), as well as a battery, charger, keyboard, LCD, and CTP-LCD for trackpad. You will need to 3D-print the case yourself. A $500 option adds the 3D printed casing parts, including bamboo plywood panels, tested and assembled. For $1,200 you get the laptop pre-assembled, including the EOMA68-A20 module. One example of a free, 3D-printable EOMA68 compliant laptop case design is this YouMagine one by Leighton.
The laptop is unusual in that it offers both a 15.6-inch LCD display and a 4.3-inch backlit capacitive touchscreen built into the QWERTY keyboard assembly. The device uses plywood panels, and is available with full schematics and 3D-printed casework design files under GPLv3 license.
Full specs for the laptop extend the EOMA68-20 COM with features including:
- EOMA68 slot (user upgradable)
- STM32F072 MCU with firmware under GPLv3 license
- 15.6-inch, 1366 x 768 LCD
- 4.3-inch capacitive backlit touchscreen (instead of mouse trackpad)
- Full-sized QWERTY keyboard including number-pad
- 3x USB 2.0 ports (2x internal) in addition to EOMA68-A20’s USB-OTG port
- 1W stereo speakers, built-in mic
- CM108AH USB audio with stereo headphone socket
- 90 x 60 x 8mm “special internal compartment”
- Triple cable set for USB, HDMI and EOMA68
- 10mAh battery (approximately 6-8 hours running time)
- 1.1 kg weight
The EOMA68 form-factor was previously used in Make Play Live’s fully open source, Allwinner A20 based Improv SBC. The Improv was developed by Aaron Seigo and the KDE Plasma Active community, the apparently defunct group that also tried and failed to finish the open source Spark and Vivaldi tablets.
“Future designs on the roadmap over the next decade include tablets, set-top boxes, video camcorders on the one hand, and EOMA68-compliant COM upgrades ranging from ultra-low-cost single core to quad-core, octal-core, and beyond as newer SoCs become readily available,” wrote Leighton in an email. “The well-known advantages of the COM strategy are brought to mass market levels.”
The EOMA68-A20 COM, mini-PC, and laptop are available for funding now on Crowd Supply, starting at $65 for the COM, with shipments due in March 2017. More information may be found at the EOMA68 Crowd Supply page and the Rhombus Tech website. The latest Crowd Supply campaign update may be found here.