Each transaction consists of two bytes. First byte - address and r/w bit. Second byte - data to be written (write transaction), or data read from internal registers (read transaction).
After reset LEDs should show 3 horisontal segments.
Read transaction: first byte is send by host, device will reply with one data byte. List of implemented commands:
Read 15:18 bits of signature: send 0x00, device will reply with 0xDA byte
Read 7:0 bits of signature: send 0x02, device will reply with 0xDE byte
Read internal register: send 0x04, device will reply with 0x00 byte (initial value of internal register is 0)
Read led register: send 0x06, device will reply with 0x49 byte (initial value of led register is 0x49)
Read status of input4-input7: send 0x08, device sill reply with byte containing state of the inputs.
Write transaction: host should send two bytes first - command, second data:
Write to internal register: send 0x05, send byte you want to write
Write to LED register: send 0x07, send byte you want to write to LED register