Did you get anywhere with this?

For a rpi2, use the image named openwrt-brcm2708-bcm2709-rpi-2-ext4-sdcard.img 
located here: https://canaan.io/downloads/software/avalon6/openwrt/latest/brcm2708/

Default IP is 192.168.0.100



You can connect without an AUC if you are using the internal iic pins on the pi.   Add " --avalon4-iic-detect" to the last line on the miner configuration page.  I have one A6 connected this way using a rpi3.  From what I’ve read you and only connect one miner this way…not sure why.  I haven’t tried because I only have one A6.  My 741’s are in a chain using an AUC.