Sipeed Tang Mega 138K Dock is a lower-cost GOWIN GW5AST FPGA + RISC-V development board

The Sipeed Tang Mega 138K Dock is a low-cost version of the Tang Mega 138K Pro development board launched last year with the GOWIN GW5AST FPGA + RISC-V SoC, two SPF+ cages, a PCIe 3.0 x4 interface, and DVI Rx and Tx ports.

The new Tang Mega 138K Dock keeps a GW5AST FPGA SoC but with a 484-ball package that fits on a smaller system-on-module, and does without the SPF+ cages, replaces the PCIe 3.0 x4 interface with a PCIe 2.0 x4 interface, and only uses a single HDMI port for DVI Rx or Tx.

Sipeed Tang Mega 138K system-on-module

Let’s first have a look at the specifications of the SoM itself:

SoC FPGA – GOWIN GW5AST-LV138FPG484A with
- 138,240 LUT4
- 1,080 Kb Shadow SRAM (SSRAM)
- 6,120 Kb Block SRAM (BSRAM)
- Number of BSRAM – 340
- 298x DSP slices
- 12x PLLs
- 16x global clocks
- 24x HCLK
- 8x transceivers at 270Mbps to 12.5Gbps
- Hard CPU – 32-bit RISC-V AE350_SOC @ 800 MHz
System Memory – 1GB DDR3
Storage – 2x 1x 128Mbit flash
Carrier board interface – 3x board-to-board connectors (2x 100-pin, 1x 80-pin)
~~Debugging – 8-pin JTAG + UART connector~~
Misc – User and “reconig,” key; Power, done, and ready LEDs
Dimensions – 45 x 34 mm (Pro was 70 x 50 mm)

Sipeed Tang Mega 138K Dock

Most of the changes can be found on the dock with changes highlighted in bold or strikethrough:

Storage – MicroSD card slot, ~~EEPROM~~
Video Input/Output
- DVI Tx/Rx ports
- LCD connector + Touch Panel connector
- ~~2x MIPI CSI connector for cameras~~
- DVP camera connector
Audio
- 2x Speaker headers
- 3.5mm stereo audio jack
- Microphone array connector
Networking
- Gigabit Ethernet RJ45 port
- ~~2x SPF+ cages~~
USB – 1x USB Type-C “Soft USB” port, 1x USB Type-A port
Expansion
- 3x 2x Pmod connectors
- PCIe 2.0 x4 edge connector (instead of PCIe 3.0)
- 40-pin GPIO header
- ~~M.2 B-key socket~~
Debugging – USB-C port for JTAG and UART
Misc
- Power button
- 4x 3x user keys
- 1x RGB LED
- ~~6x user LEDs~~ (Note: LEDs can be added through one of the Pmod connectors if needed)
- Fan connector
- 6-position DIP configuration switch
- 2x gamepad connectors
Power Supply
- 12V via DC jack
- Battery connector for 3.7V LiIon battery
Dimensions – 147.1 x 93.2 mm

While some features have been cut, there have been some improvements and additions including two gamepad connectors, a touch panel connector, a USB Type-A port, a 3.7V battery connector, and a DIP switch for configuration. All photos also show the Tang Mega 138K with a heatsink (fanless) while the Tang Mega 138K Pro is actively cooled with a small fan.

The wiki is being translated and most information is about the earlier Tang Mega 138K Pro, but details about the Tang Mega 138K should be up very soon. In the meantime, you’ll find some documentation on the download page. I can also see Sipeed is working on a Tang Mega 60K model. The new Tang Mega 138K has been designed for retrogaming consoles with LCD and TP connectors, two joysticks, a stereo speaker, and battery management. You’ll find some code samples specific to the new FPGA board on GitHub, and an example of emulator running on Sipeed Tang boards is MiSTeryNano Atari STE emulator.

Sipeed is selling the Tang Mega 138K Dock with an acrylic enclosure on Aliexpress for $129.60, where you’ll find the module only for $68.80. Europeans will need to wait for a few days for the board to become available as the company is working through red tape, and users may see a 404 error page in the meantime. Accessories such as a camera and a power supply are available on a separate page. For reference, the earlier Sipeed Tang Mega 138K Pro Dock is sold for about $200 on Aliexpress and Amazon.

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.