Adding Wi-Fi to Emcraft Systems K70 SoM

Emcraft Systems K70 SoM is a system-on-module powered by Freescale K70 Cortex M4 micro-controller with enough RAM (64 MB) to comfortably run uClinux. They used to charge $99 for their uCLinux BSP, but it’s now free of charge, and the company also provides full hardware and software documentation, including a getting started guide, schematics and BoM for the baseboard, application notes and more…

Many of their clients want to use Wi-Fi with K70 SoM, and it can easily be done by using Wi-Fi USB dongles based on Ralink RT5370 chipset such as D-Link DWA-140 (H/W rev B3) or Comfast CF-WU815N.

Emcraft has provided detailed instructions to do so with K70 SoM, their latest baseboard (SOM-BSB-EXT) and a demo image based on their uClinux BSP. I’ll summarize the instructions to use K70 SoM as a Wi-Fi access point below.

1. Connect the baseboard and K70 SoM with an Ethernet cable, a mini USB to USB Y-cable for power and serial console, a mini USB to USB female and a Wi-Fi USB dongle as shown in the picture below.
2. Download the kernel image with Wi-Fi enabled, copy it to to your TFTP server, and download the image via tftp, flash it to the SoM’s NAND flash, and reset the board
3. The image contains the following script (start_ap) to start a Wi-Fi access point:
   
   #!/bin/sh echo "Starting AP" ifconfig wlan0 192.168.1.1 up ifconfig wlan0 hostapd /etc/hostapd-minimal.conf & echo "Starting DHCP server" udhcpd -f /etc/udhcpd.conf &

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   #!/bin/sh   echo "Starting AP" ifconfig wlan0 192.168.1.1 up ifconfig wlan0 hostapd /etc/hostapd-minimal.conf & echo "Starting DHCP server" udhcpd -f /etc/udhcpd.conf &

   
   as well as a minimal hostapd configuration file (/etc/hostapd-minimal.conf) for a non-encrypted k70 access point:
   
   #change wlan0 to your wireless device interface=wlan0 driver=nl80211 ssid=k70 hw_mode=g max_num_sta=255 channel=2

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   #change wlan0 to your wireless device interface=wlan0 driver=nl80211 ssid=k70 hw_mode=g max_num_sta=255 channel=2

   
   Simply run ./start_ap to start the daemon

Done. You should now see k70 with any Wi-Fi enabled device (laptop, smartphone,…), be able to connect to this unsecured network, and get an IP via DHCP on this subnet.

Emcraft posted some Wi-Fi throughput benchmarks done in the wireless LAN:

• FTP transfer (FTP server to K70 SoM with wget) – 772.652 KB/s.
• NFS transfer (NFS host to K70 SoM) – 1076.92 KB/sec

The connection was tested in 802.11g mode, and the Wi-Fi connection rate was reported to be 54 Mb/sec.

Disclosure: This post has been sponsored by Emcraft Systems.

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