A quick analysis of wifi cards for using a Raspberry Pi as an access point

When Radiodan can’t access the web, it throws up an access point (AP) created by the Pi: you connect directly to that and it displays the available wifi points in a webpage as a captive portal, and asks you to add the password for the one you want. It’s not easy to get credentials for wifi to objects with no user interface, and this is the best one we’ve found so far (Chromecast does something similar).

However our home tests suggest that the many varieties of wifi USB cards and access points cause problems of two major kinds. One a general problem of Radiodan accessing the internet – the wifi access point in a house might just be too far away. The other is that some wifi cards don’t seem to work as access points properly, and we wanted to get to the bottom of where the problems were there, as identified with the kind help of Giles Booth (@blogmywiki). This is so that we can recommend wifi cards to go with Radiodan or at least so we can say which are known to work.

I’ve started on the second problem here. I had 6 USB wifi cards in the house of various kinds: left to right: Wipi, Comfast, Micronet, Tenda, Loglink, Edimax

Here’s what I found for each.

Test setup:

• 5 metres from an apple wifi point
• Mac OS 10.9.5 Macbook Air laptop
• 30 cm between laptop and Pi

Test conditions:

• Radiodan clean image, boot up, try and connect to the radiodan-configuration AP from laptop

Results

So basically I found two different manufacturers, Ralink and Realtek and the Realtek ones don’t work as APs with our setup.

It should be possible to get the Realtek ones working – there’s a detailed description here – and I managed to get a network showing up using those instructions but within our framework, but I couldn’t connect to it – so we’ll have to test this some more.

How to find your wifi card’s chipset

The best way it to plug it into a Raspberry pi that you are already connected to and type:

$ pi@radiodan ~ $ lsusb

This will give you a list of everything connected to USB, in my case (I had two wifi cards connected):

Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. 
Bus 001 Device 004: ID 148f:5370 Ralink Technology, Corp. RT5370 Wireless Adapter
Bus 001 Device 006: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN Adapter

On Mac OS X you can look in apple menu -> about this mac -> more info -> system report and then click on USB – but you’ll need to google the vendor name and id to get the chip.