test max7219
        protocol-decoder spi channel miso=0 channel cs=1 channel mosi=2 channel clk=3
        protocol-decoder max7219
        stack spi max7219
        input spi/max7219/max7219.sr
        output max7219 annotation class register match max7219_register.output
        output max7219 annotation class digit match max7219_digit.output
        output max7219 annotation class warning match max7219_warnings.output