START
115200, baud rate, from 1200,2400 ~ 57600,115200
N, N=No Parity, E=EVEN, O=ODD
1, 1=one STOP bit, 2=two STOP bits
100, TimeOut for Modbus command, format=Dec, valid=[0 ~ 255], unit=0.01 sec, 0.01x100=1 sec, max=2.55 sec
0, delay in the end of Modbus command, format=Dec, valid=[0 ~ 255], unit=0.01 sec, max=2.55 sec
0, InTxPdoMax/2, format=Dec, valid=[0 ~ 128], default=0=Auto
0, OutRxPdoMax/2, format=Dec, valid=[0 ~ 128], default=0=Auto
0 0 0 0 0 0 0, 7 Reserved, format=Hex, default=0
4, 4 commands(00-03), max=300, format=Dec
04 03 10 03 00 01, 2F, 00, 00, InTxPdo[2F]=PT_ratio, update cyclically, (00)
04 03 10 04 00 01, 30, 00, 00, InTxPdo[30]=CT_ratio, update cyclically, (01)
04 06 10 03 00 00, 02, 00, 08, PT_ratio=OutRxPdo[2], state change update(02)
04 06 10 04 00 00, 03, 00, 08, CT_ratio=OutRxPdo[3], state change update(03)
STOP 
==========================================================================
OutRxPdo[00]=CTL, OutRxPdo[01..7F]=Out[01..7F] 
InTxPdo[00]=SYS,  InTxPdo[01..7F]=In[01..7F] 
==========================================================================
16_bit commands
set PT_ratio will save to EEPROM --> can not use update cyclically --> must use state change update
set CT_ratio will save to EEPROM --> can not use update cyclically --> must use state change update

address of power_meter = 04