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LM811: Power supply FAQ

Question:

The power supply on the board will supply the required current for the module, but do I also need to add any decoupling caps close to the supply pins of the module? Or are they already on the module, and all i need to supply is the +3.3V to the module?

Answer:

  • The LM811 doesn’t require any additional capacitors as long as the correct voltage is being used.

 

Question:

I’ve ordered the WIFI/BT combo-module LM811 with IPEX connector. In the datashaeet I found, that the DC power input is 3.3V. Is it possible to connect a 5V USB interface to the module? Are the USB D+ and D- inputs 5V tolerant? 

Answer:

  • It should be fine. However we do not recommend it as it is very easy to damage the module with the wrong voltage signals.

 

Question:

I’m designing the LM811-0461 into a new design.  I’m not intending to use the WO-WLAN, SUSPEND or BT_PCM functionality, I just want to connect power and USB.  I would like advice on how to connect the unused signals. The BT_PCM_IN pin is documented as an input – should I tie this to ground to prevent the input from floating?

Answer;

  • All unused pins can be left unconnected. It is not necessary to tie them to ground.

 

Migrating to the LM811

How to migrate from the LM820/821/822/823 to the LM811?

The LM811 and LM820/821/822/823 have the same dimensions of 25mm x 12mm x 2mm and the USB interface (pin 2 to pin 5) are in exactly the same position.

When moving to the LM811, consider the following:

  • Pin 1 and Pin 6 have different pin assignments to LM820/821/822/823 .
  • The LM811 has extra pins for a PCM interface. If PCM is not required, this will not affect the design.

Please refer to the datasheets for further information.

 

 

LM811: Linux driver installation

WiFi

The WiFi driver can be downloaded from here: https://github.com/lwfinger/rtl8723bu If you are compiling on the Raspberry Pi 2 or another ARM device you will need to change the SUBARCH build parameter in the Makefile to “arm”.

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Linux WiFi Ad-hoc mode

Ad-hoc, or IBSS mode allows you to create a wireless network without a central access point. This guide demonstrates a simple Ad-hoc network using one of our adapters and some basic tools found in most modern Linux distributions.

  • At the present time, IBSS may suffer from high levels of packet loss due to an issue with the driver.

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