If the BV4111 works okay with a PC the it is probably how the bytes are terminated on the openwrt. To explain the BV4111 expects a 'packet of information terminated with byte 13, so command so to turn on relay 'c' on a PC terminal would be:
"dc1,0"
The actual bytes sent to the BV4111 would be 100 99 49 44 48 13 (in decimal). If openwrt sends these bytes at the correct Baud rate then the BV4111 WILL work. It may be just sending LF (10) or LF+CR after sending the command bytes.
