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MXM3-enabled RK3399 board blurs lines between SBC and COM

Jul 24, 2018 — by Eric Brown 2,328 views

The “Khadas Edge” SBC runs Linux or Android on a Rockchip RK3399 and offers WiFi/BT, HDMI 2.0, USB 3.0 and 2.0, and dual USB Type-C ports, as well as an MXM3 connector to plug into an upcoming “Khadas Captain” carrier.

Shenzhen Wesion’s Khadas project has posted specs for a “Khadas Edge” board that combines attributes of both a single board computer and a computer-on-module. Unlike the Amlogic based Khadas Vim and Khadas Vim2 SBCs, the Khadas Edge features the hexa-core Rockchip RK3399. Presumably, the Khadas Edge will be an open-spec board like the similarly dimensioned, 82 x 57.5mm Vim models. OS support includes Android Oreo, Ubuntu 18.04, and Debian 9.0 with mainline Linux.

Khadas Edge front and back
(click images to enlarge)

We have previously referred to minimalist SBCs such as the Raspberry Pi Zero as being COM-like because they offer only limited coastline ports. In the case of the Khadas Edge, however, the board has plenty of real-world ports, but also integrates a 314-pin MXM3 edge connector, which is protected by a removable cover. MXM3 connectors are found on SMARC modules, such as iWave’s i.MX8 QuadMax based iW-RainboW-G27M.

The Khadas Edge will plug into a Khadas Captain baseboard but can also be used as a standalone SBC. The Khadas Edge and Khadas Captain will launch in a crowdfunding campaign in August, according to the CNXSoft story that alerted us to the product.

Khadas Edge
(click image to enlarge)

The closest competitor for the combined Edge/Captain product would be Vamrs’ Rockchip RK3399 Sapphire SBC when deployed sandwich style on the optional Excavator EVB Kit. The other RK3399 boards we’ve seen, such as the Orange Pi RK3999 are monolithic SBCs, although there has also been at least one COM: Theobroma’s RK3399-Q7.

GeekBox board plugging into GeekBox Landingship carrier board

As noted by CNXSoft, Shenzhen Wesion is also the company behind the open-spec GeekBox SBC and mini-PC, which similarly adds an MXM3 golden finger to a Rockchip-based SBC. The MXM3 connector on the RK3368 based GeekBox plugs into an optional Landingship carrier board.


The Khadas Edge will be available in Basic, Pro, and Max models, each with different combinations of RAM and eMMC ranging up to 4GB/64GB. The Pro and Max models also boost the wireless to a new Broadcom AP6938S module that boosts the Bluetooth to 5.0 and enhances the dual-band WiFi-ac with RSDB (real simultaneous dual band) technology. RSDB permits simultaneous independent operation of the 2.4GHz and 5GHz bands, thereby enabling streaming of a game to a smartphone while streaming video from the smartphone to a smart TV. In automotive applications, it would dedicate the 5GHz band for infotainment and in-vehicle use while using the 2.4GHz band for a WiFi hotspot.

All three models of the Khadas Edge provide a 4K-ready HDMI 2.0a port, as well as dual USB Type-C ports, one of which supports DisplayPort 1.2. The other Type-C port is dedicated to power, although you can also draw the wide-range power from onboard Pogo Pads or the MXM3 gold finger.

The Khadas Edge is further equipped with USB 3.0 and 2.0 host ports and dual 10-pin FPC expansion connectors. The FPC B connector supports the Edge’s onboard 8-bit STM8S003 MCU with programmable EEPROM. It appears that the FPC A connector will support a new Edge IO daughter board, which will enable serial debug, as well as easier GPIO expansion.

Edge IO board
(click image to enlarge)

The MXM3 connector, meanwhile, supplies the full panoply of the RK3399’s I/O to the undocumented Khadas Captain board. These include high-speed interfaces like PCIe, eDP, DVP, and MIPI-CSI and -DSI. It also enables the Edge’s GbE controller to express itself via a real-world RJ45 port on the Captain. The lack of an RJ45 on the Edge itself enables a thin, 5.7mm profile.

Preliminary specifications listed for the Khadas Edge include:

  • Processor — Rockchip RK3399 (2x Cortex-A72 at up to 2.0GHz, 4x Cortex-A53) with Mali-T860 GPU; 8-bit STM8S003 with programmable EEPROM
  • Memory:
    • Basic — 2GB LPDDR4 RAM, 16GB eMMC 5.1
    • Pro — 4GB/32GB
    • Max — 4GB/64GB
    • All models — 16MB SPI flash
  • Wireless:
    • Basic — 802.11b/g/n/ac 2.4GHz/5GHz 2×2 MIMO with Bluetooth 4.1 (Broadcom AP6356S)
    • Pro and Max — 802.11b/g/n/ac 2.4GHz/5GHz 2×2 MIMO with RSDB and Bluetooth 5.0 (Broadcom AP6938S)
    • 2x WiFi antennas
  • Networking — GbE controller with WoL (PHY only, no port)
  • Display/camera:
    • HDMI 2.0a port with CEC for up to up to 4K@60Hz, HDCP 2.2
    • DisplayPort 1.2 available via 1x USB Type-C
    • Simultaneous dual display support
  • Other I/O:
    • 2x USB 3.0 Type-C ports (1x power only, 1x with DP and USB support)
    • USB 3.0 host port
    • USB 2.0 host port
    • Fan header
  • Expansion:
    • FPC connector A — UART, I2C, SPI, SD/MMC, ADC, PWM, IOs
    • FPC connector B — USB, I2S (8 ch.), I2C, MCU IOs
    • 314-pin MXM3 board-to-board connector
  • Other features — 3x buttons; 2x LEDs; heatsink (TBC); optional Edge IO and Khadas Captain boards
  • Power — 5-20V DC input via USB Type-C, Pogo Pads, MXM3; 2-cell battery module
  • Weight — 25 gm
  • Dimensions — 82.0 x 57.5 x 5.7mm
  • Operating system — Android Oreo, Ubuntu 18.04, Debian 9.0, etc. with mainline Linux and U-Boot; support for TensorFlow and Android NN (Neural Networks API)

Further information

The Khadas Edge will launch on a crowdfunding site in August at an undisclosed price. More information may be found on the Khadas project’s preliminary Khadas Edge product page.

(advertise here)

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One response to “MXM3-enabled RK3399 board blurs lines between SBC and COM”

  1. Jonathan Miller says:

    A better arrangement in my opinion would have been to replace one of the 3 USB ports with the Ethernet port, instead of relegating Ethernet to the gold finger connector. Having to design and build a carrier board is a pretty high price to pay just to get access to an Ethernet port. Sacrificing one USB port in favor of Ethernet would seem to be a big improvement in value. A lot more applications could then be served without having to design a carrier board.

    This board doesn’t seem to be an ideal solution for either an SBC application or a COM application. If I were looking for an SBC, I’d want all I/O features to be readily accessible without having to design a baseboard. That’s the whole purpose of an SBC. And if I were looking for a COM, I’d want first the use of an open standard, which gives me the ability to interchange with other modules from other suppliers, and secondly the freedom to put all I/O connectors wherever I want them, instead of being stuck with the types and positions chosen by the board vendor. Those are the two primary reasons for choosing a COM. It seems that by trying to serve two masters, this board excels at neither.

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