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Voice boards run Linux on Cortex-A35 based RK3308

Jun 14, 2019 — by Eric Brown 2,641 views

Hangzhou Wild Chip Tech has launched two open-spec “MDK3308” dev kits with 6-mic arrays that extend a Linux-driven “Mcuzone MDK3308 Coreboard” module running a quad -A35 Rockchip RK3308.

Over on AliExpress, there’s a new Mcuzone MDK3308 Coreboard module featuring a Cortex-A35 based Rockchip RK3308 SoC. The Mcuzone MDK3308 Coreboard sells for $23 (256MB RAM) or $26 (512MB) with 256MB NAND flash and 8GB eMMC. The module is also available in two open-spec, sandwich-style evaluation kits starting at $35.

Mcuzone MDK3308 Coreboard (left) and MDK3308-EK
(click images to enlarge)

It’s unclear whether Hangzhou Wild Chip Ltd. Store is the manufacturer or only a third-party distributor/store. On AliExpress, Hangzhou sells a variety of Mcuzone branded Atmel, NXP, and TI-based boards, but also sells FriendlyARM (FriendlyElec) NanoPi boards.

The MDK3308-EK dev kit feaures a 6-microphone array for voice applications, and ranges from $69 to $109 with 512MB RAM. The prices depend on options including a camera ($90), a 4G radio ($100), and a “C70” SKU with a 7-inch touchscreen ($109).


We found out about the Mcuzone MDK3308 Coreboard and MDK3308-EK Evaluation Kit on CNXSoft, but the story did not mention the second, $35 MDK3308-Prog board eval kit option for the module, which was hidden away in the somewhat confusing product pages. The smaller MDK3308-Prog, which similarly includes a 6-mic array, uses a stripped-down version of the MDK3308 Coreboard that’s limited to 256MB RAM and 256MB NAND, but with no eMMC.

MDK3308-EK-C70 (left) and MDK3308-Prog
(click images to enlarge)

These appear to be open-spec boards. There’s an extensive Mcuzone downloads page, with most of the documentation in Chinese. The products ship with Linux Kernel 4.4.154 with Qt 5.9, U-Boot, and other components.

Rockchip RK3308

Arm’s low-power, 64-bit Cortex-A35 architecture is finally getting some attention with NXP’s i.MX8X SoC launching on a variety of compute modules and a 96Boards compatible Arrow AI-ML Board SBC. Rockchip has also adopted the Cortex-A35 architecture in its quad-core Rockchip PX30 and RK3326 SoCs, and will soon deploy it in a dual-core RK1808 SoC that includes a neural processing chip. The RK1808 is due to appear in a 96Boards SOM form factor TB-96AIoT module.

Rockchip RK3308 block diagram and MDK3308-EK with UVC camera option
(click images to enlarge)

The quad-core, 1.3GHz Rockchip RK3308 lacks a 2D or 3D accelerated GPU, but it supports 1024 x 600-pixel (RGB) and 1280 x 720 (LVDS) displays, which are available on the MDK3308-EK. The voice-oriented SoC offers audio interfaces including I2S, PCM, TDM, PDM, SPDIF, and HDMI ARC.

The Mcuzone board specs mention an “AI VA” feature without explanation. If this is some sort of AI video acceleration technology, it does not appear to be documented on the RK3308 chip.

The RK3308 was announced with a similar RK3326 SoC, which adds a low-power, 2D Mali_G31 MP2 GPU. The RK3326 is faster, at 1.5GHz, and supports a higher 1920 x 1080 resolution.

Mcuzone MDK3308 Coreboard

The Mcuzone MDK3308 Coreboard, which is variably listed as 65 x 45mm and 60 x 45mm, combines the RK3308 with 256MB or 512MB RAM (DDR3 or DDR3L), as well as 256MB NAND flash. When sold separately, the module includes 8GB eMMC.

As noted, however, one of the dev kit models omits the eMMC, and there’s also mention of a 4-16GB eMMC range. The 6-layer module has a 5V DC input and an RK816-3 power management unit. I/O is expressed via 200 GPIO pins arrayed on either side of the module.

MDK3308-EK Evaluation Kit

The 180 x 130mm MDK3308-EK Evaluation Kit builds upon the Mcuzone MDK3308 Coreboard with an SD slot and a 10/100 Ethernet port. There’s also an SDIO-based, dual-band WiFi module with Bluetooth 4.1 module and an antenna.

The MDK3308-EK is equipped with 3x USB 2.0 host ports deployed via a hub. There’s also a full-size USB 2.0 OTG port, which can only be used if you’re not using the adjacent micro-USB OTG port. In addition, there’s a micro-USB serial console port and a TTL debug interface with jumper.

MDK3308-EK detail view (left) and equipped with external 4G option
(click images to enlarge)

The board is notable for its analog 6-mic audio array. Other features include an audio jack, 3x UARTs, a temperature sensor, 5x ADC user buttons, a reset button, 5x LEDs, and a Li-ion battery interface. An LCD connector supports an a 7-inch, HD capacitive touchscreen, which is available on the $109 C70 SKU.


The $35 MDK3308-Prog dev kit uses a version of the MDK3308 Coreboard with 256MB RAM and NAND, but no eMMC. This smaller, 107 x 68mm sports the 6-mic array found on the MDK3308-EK. It appears to be designed to act as a mainboard for a compact voice activation device.

MDK3308-Prog and detail view
(click images to enlarge)

The MDK3308-Prog has a more limited feature set than the EK model. There’s a USB 2.0 host port with USB-based WiFi dongle and a micro-USB OTG port with power support. There’s also an audio-out jack, a pair of UARTs for debugging, a power switch, 2x user buttons, and 2x LEDs.

Further information

The Mcuzone products are available on AliExpress via the Hangzhou Wild Chip Ltd. Store. The Mcuzone MDK3308 Coreboard sells for $23 (256MB RAM) or $26 (512MB). The MDK3308-EK dev kit ranges from $69 to $109, and the MDK3308-Prog sells for $35. More information may be found on this Hangzhou Wild Chip Mcuzone MDK3308 launch page.


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