how to send command and debug with KC868-COLB by yourself

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how to send RS485 command to KC868-COLB. 
Let's see an example: How to read data of electric energy meter by KC868-COLB via RS485 ModBus


1. Read power consumption:
Example:
Send:
5E 01 03 C0 08 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 00 00 00 02 CE 40

5E 01 03 C0 is fixed, never change. 5E 01 is begin byte, 03 C0 is command for RS485.
08 00 is message command length, now it's 8 bytes.
38pcs of "00" is reserved area for furture.
7A 03 00 00 00 02 CE 40  is send for power meter, this is ModBus protocol
7A hex->dec is 122.  122 is power meter address ID.

Feedback:
5E 01 03 C0 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 04 42 53 33 33 81 B8

7A 03 04 42 53 33 33 81 B8

7A hex->dec is 122.  122 is power meter address ID.
03 is Modbus function: read    04 is length of data      81 B8 is CRC code
42 53 33 33 is float , need convert to dec, 0x42533333 is 52.8 Kwh

          

2. Read power voltage:
Example:
Send:
5E 01 03 C0 08 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 00 64 00 02 8F 9F

Feedback:
5E 01 03 C0 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 04 43 5C 00 00 E4 A2


7A 03 04 43 5C 00 00 E4 A2
43 5C 00 00 is float , need convert to dec, 0x435C0000 is 220V

3. Read power current:
Example:
Send:
5E 01 03 C0 08 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 00 6A 00 02 EE 5C

Feedback:
5E 01 03 C0 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 04 3F 99 99 9A 07 34


7A 03 04 3F 99 99 9A 07 34
3F 99 99 9A is float , need convert to dec, is 1.2A

4. Read power:
Example:
Send:
5E 01 03 C0 08 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 00 76 00 02 2F 9A

Feedback:
5E 01 03 C0 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 04 3F 5C 28 F6 63 74

7A 03 04 3F 5C 28 F6 63 74
3F 5C 28 F6 is float , need convert to dec, is 0.86kw

5. Read power factor:
Example:
Send:
5E 01 03 C0 08 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 00 8E 00 02 AE 6B

Feedback:
5E 01 03 C0 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 04 3F 73 33 33 98 1E


7A 03 04 3F 73 33 33 98 1E
3F 73 33 33 is float , need convert to dec, is 0.95Q

6. Read power frequency:
Example:
Send:
5E 01 03 C0 08 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 00 90 00 02 CE 6D

Feedback:
5E 01 03 C0 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 7A 03 04 42 48 0A 3D 62 2B


7A 03 04 42 48 0A 3D 62 2B
42 48 0A 3D is float , need convert to dec, is 50.01Hz