Contents:

Ralink 3071

Teardown

Chips

Mechanical design

Switching power supply

Linux support

Images

Related: A-Link WL54USB wireless teardown

Ralink 3071

Bulk 802.11 b/g/n Mini size Wireless LAN USB2.0 Adapter available from Hong Kong resellers identifies itself as USB ID D-Link 3071. It seems to be available in several brands.

Teardown

Opening the case required a bit of violence. With a bit of caution, it is possible without damaging the case (my procedure caused a small dent on the USB frame plate). I did not find any broken latches, so I suspect that the case was fastened by a small amount of glue.

Chips

It is very small, uses a low power Ralink RT3070L chipset, has a small chip antenna and a dual switching power supply using Eutech Microelectronics EUP3409 (equivalent of MP2109 from Monolithic Power Systems) chip for stepping down the power voltage. It is a good candidate for a conversion to a small embeddable WLAN USB module.

Mechanical design

The mechanical design is interesting as well. More than a half of the PCB is hidden inside the connector in the area that is normally filled by the plastic insulation. Ferrites of coils in the switching power supply act as an spacer between the PCB and the USB connector frame and prevents a very thin PCB from distortion. The PCB has at least four layers.

The board is equipped with 2 LEDs.

Switching power supply

It seems to be possible to implement external on/off switch without any external parts: Look at two 0201 resistors wired to pins 1 and 6 of the EUP3409. They provide pull-up for the Enable switches. If one breaks the connection between these resistors and pins 3 and 8, then the control voltage wires can be soldered to these resistors. These resistors seems to be about 100 and 150 kΩ. Half of the connection is located on the top layer, so it seems to be possible to cut the PCB trace there. However, resistors are pretty tiny. Guessing whether it would be better to use a tiny soldering iron or a soldering paste for adding the enable wire.

Linux support

To get a perfectly working driver, you need the latest kernel.

There are two drivers:

Images

Ralink 3071
Ralink 3071 top part of PCB (ambient light) Ralink 3071 top part of PCB (light on left) Ralink 3071 top part of PCB (light on top)
Ralink 3071 bottom part of PCB (ambient light) Ralink 3071 bottom part of PCB (light on left) Ralink 3071 bottom part of PCB (light on top)