Current Mesa Modbus issues:

    
    BUGS:
    At startup there can be "call/response function number missmatch" 
    error popups or sig11 (segv)s due to the fact that the PKTUART is 
    not cleared at startup, so random numbers of garbage characters 
    may be present in the RX FIFOs, leftover from the last LinuxCNC run.
    
    A temporary workaround is to run this before launching linuxcnc:
    
    mesaflash --device cardname --addr ipaddr --wpo 0x6800=0x00010000
    
    (writing 0x10000 to 0x6800=pktuartr_mode_reg clears the RX FIFOs)

    If you ever set the update rate to 0 (maximum), changing to a 
    non-zero rate will not work (communication stops)
    
    There is a check for TX overflow in the PKTUART code that's 
    in the wrong location (TX section) so will print bogus error 
    messages with particular outgoing messages.
    
    FEATURES:
    
    Channel setting should not be global but in the .mod file
    to support more than one device.
    
    It would be good to have the error timeout/recovery
    time programmable.
    
    For multiple reads/writes it would be good to have the 
    possibility of mixed types,
    This means for modbus devices that support table reads, 
    all I/O for a device could be done in a single read and a single 
    write.