These use a Ralink chipset that only has preliminary support and requires a manual build. D1/D2 models are known to have problems with the latest ethernet driver(s) and require the use of an older driver. D3/D4 are relatively stable with an unmodified trunk build.
How to enter UBOOT mode:
When you press RESET button for Disconnect the power,
Then turn on the power, after 10 seconds release the power.
Hardware Highlights
Revisions: D4
CPU: Ralink
Ram: 32MB
Flash: 4MB
Updated D4 install instructions (AArc2) are here: https://forum.openwrt.org/viewtopic.php?id=35184
