HLK-7688A OpenWrt Development Board Comes with an Audio Jack

We first tested MediaTek MT7688 MIPS processor in Mediatek Labs’ LinkIt Smart 7688 / 7688 Duo hardware development kits running OpenWrt in 2015 with the boards having a focus on IoT applications. A year later, Widora NEO board launched with an audio jack for connected audio applications, but AFAIK it’s not available anymore.

There’s now another OpenWrt audio board based on the processor with HLK-7688A board featuring Hi-Link HLK-7688A module which we previously found in MatchBox LoRaWAN gateway.

HLK-7688A Development Board

HLK-7688A board specifications:

  • Wireless Module – HLK-7688A based on MediaTek MT7688 MIPS24KEc processor @ 580 MHz, and equipped with 128MB RAM, 32MB flash
  • Storage – MicroSD card slot
  • Connectivity
    • 802.11 b/g/n WiFi 4 up to 150 Mbps with u.FL antenna connector
    • 10/100M Ethernet
  • Audio – 3.5mm audio jack; 4-pin speaker header, WM8960 audio codec
  • USB – 2x Micro USB ports one USB 2.0 port and one for debugging & power
  • Expansion – 2x 26-pin headers with GPIO’s, SPI, UART, I2C, I2S, Ethernet, USB, GND, 3.3V…
  • Misc – 4x status LED’s for WiFi, LAN, USB, and WiFi; reset button, factory reset button (long press)
  • Power Supply – 5V via Micro USB port
  • Dimensions – Module: 32.8 x 18 mm; Board (est): 75 x 34 mm

HLK-7688A Board Pinout

The board is apparently sold as a video and/or audio streamer storing files in USB storage or MicroSD card to be played on your phone. Up to 8 phones are supported for photo sharing, and 3 phones for simultaneous video streaming.

One of the photos of the board shows it supports OpenWrt 3.10 with Linux 2.6.36 SDK. It’s probably a mistake, as when I tested the MediaTek LinkIt board two years ago, it ran Linux 3.18.21, OpenWrt Chaos Calmet 15.05+.

One buyer also mentions USB audio works just fine with Linkit firmware, and the latest version of OpenWrt can run on the board but without I2S nor I2C support. He later updated his comment with further details:

Openwrt driver support is left at v15 and even this version 15 is full of bugs. I2S is “mission impossible” andI could not get sound out of that board

If despite the software shortcomings, you’re still interested in the board, it can be purchased for $16.70 with WiFi antenna on Aliexpress, or alternatively you could get the module only for $10 shipped from the same link.

As a side note, while looking for other HLK-7688A boards on Aliexpress, I came across one with 5 Ethernet ports since the processor supports this.

The router board above can be purchased for $17.55 including shipping.

Thanks to Fran for the tip

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