We use a modified version of this library to implement the first SHA256 multi+merge mining pool.

It works just fine with the S7 which has CGMiner 4.8 ("cgminer/4.8.0"). However, the S9 with BMMINER 2 ("bmminer/2.0.0") is either unable to connect, either connects, and remains on the initial difficulty of shares, and thus all work gets rejected.

We suspect that the BMMINER does not support the set_difficulty method. The question is, how can this be solved? can we use s7 firmware for s9, or find a CGMiner compatible with S9 anywhere?