Crossposting this from the HOWTO forum since questions aren't supposed to be posted there.

So, this device is in the table of supported hardware but there is no information on exactly how to install OpenWRT.  The build flow only produces "openwrt-ramips-rt305x-wcr150gn-squashfs-sysupgrade.bin" but no "factory" image is created.  How do I get OpenWRT onto the device in the first place?  I tried using the generated OpenWRT bin file with the SparkLAN firmware upgrade web interface but it detects it as invalid firmware and aborts the process.
Does the stock SparkLAN firmware have a bootloader that I can interact with (tftp maybe)?

Updating this in case someone else runs into this problem ...

To load OpenWRT you need to connect to the board using the serial port. (4-pin header on the card).  The serial port runs at 57600, 8 bit data, 1 stop bit, no parity.  During the boot process a menu is displayed in the serial output and you can select to load a firmware image using tftp.

The SparkLAN device is a tftp client so you'll need to configure a tftp server on your Windows/Linux host.  I was using Windows so I downloaded Solarwind's free tftp server.  I placed the sysupgrade OpenWRT image in the root directory for the tftp server.  After that it was simply a matter of configuring the host and device IP addresses when prompted by the bootloader.  The bootloader copies the image through tftp, erases flash and then copies OpenWRT over.  (Hooray.)

Now I just need to learn how to configure OpenWRT ...