Mediatek LinkIt Smart 7688 and Smart 7688 DUO Boards Run OpenWRT for IoT Applications

MediaTek LinkIt is a collection of development platforms designed for the prototyping of wearables and Internet of Things (IoT) devices, and last year they started with LinkIt ONE board based on Mediatek MT2501 “Aster” micro-controller and featuring WiFi, Bluetooth, GPSD and GSM/GPRS connectivity. Mediatek Labs has now launched two new LinkIt board, namely LinkIt Smart 7688 and LinkIt Smart 7688 DUO, both powered by Mediatek MT7688 MIPS processor and running OpenWRT, with the latter also adding an Atmel ATmega32U4 for Arduino compatibility.

LinkIt Smart 7688 Board

LinkIt Smart 7688 is then the simpler of the two with the following specifications:

• Processor – Mediatek MT7688AN MIPS24KEc processor @ 580 MHz with WiFi
• System Memory – 128MB DDR2 RAM.
• Storage – 32MB flash + micro SD slot
• Connectivity – 1T1R Wi-Fi 802.11 b/g/n with chip antenna and I-PEX conector
• USB – 1x micro USB host port, 1x micro USB port for power
• Expansion – 2x 18-pin headers with GPIOs, I2C, I2S, SPI, UART, PWM and Ethernet Port.
• Misc – MPU reset and WiFi reset buttons, MPU EJTAG solder pads
• Power Supply – 5V via micro USB port, or 3.3V via header
• Dimensions – 55.7 x 26 mm

CL245A on the back of the board is a switch IC to “bypass MT7688AN bootstrap behavior”.

LinkIt Smart 7688 DUO

The DUO board is pretty similar, and adds Atmel MCU and reset button, 4 more I/O pins, and is slightly longer:

• Processor – Mediatek MT7688AN MIPS processor @ 580 MHz with 64 KB I-cache, 32 KB D-cache
• System Memory – 128MB DDR2 RAM.
• Storage – 32MB flash + micro SD slot
• MCU – Atmel ATmega32U4 AVR @ 8 MHz
• Connectivity – 1T1R Wi-Fi 802.11 b/g/n with chip antenna and I-PEX conector
• USB – 1x micro USB host port, 1x micro USB port for power
• Expansion – 2x 20-pin headers with GPIOs, I2C, I2S, SPI, UART, PWM and Ethernet Port.
• Misc – MPU reset, MCU reset, and WiFi reset buttons, MPU EJTAG solder pads
• Power Supply – 5V via micro USB port, or 3.3V via header
• Dimensions – 60.8 x 26 mm

The I/Os pin are however connected quite differently on 7688 and 7688 DUO, as the latter has most IOs connected to the AVR MCU, with only 3 GPIOs directly connected to the MIPS processor.

Documentation for both board is pretty extensive with Getting Started Guides, a developer’s guide, tutorials, and information about the HDK (Hardware Developer Kit) , which is simply call “board”, including schematics and PCB layout (PDF only). The company also released the bootloader and firmware binary files, as well as an OpenWRT SDK. The boards support both Linux and OS X for development with C/C++, while Python, and Node.js are also supported on Windows. Arduino IDE is also available for the DUO version, and by default MT7688 MPU and Atmel MCU communicate over UART with applications code on the former, and I/Os and sensors managed by the latter. You can access all these resources on LinkIt Smart 7688 page on MediaTek Labs, with some code also found on Mediatek Labs’ Github account, and Seeed Studio’s Wiki. You could also read my own little Linkit Smart 7688 Getting Started Guide.

LinkIt Smart 7688 boards are distributed by Seeed Studio, and you can purchase Mediatek LinkIt Smart 7688 for $12.90 and LinkIt Smart 7688 DUO for $15.90.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.

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