root@orangepi3:/# modbus_client --debug -mrtu -pnone -s1 /dev/ttyUSB0 -a0x01 -t0x03
Opening /dev/ttyUSB0 at 9600 bauds (N, 8, 1)
[01][03][00][64][00][01][C5][D5]
Waiting for a confirmation...
ERROR Connection timed out: select
ERROR occured!
root@orangepi3:/#