​​Huanyang VFD “modbus” protocol
​​
​​This is a work-in-progress living document, based on a copy of the Huanyang VFD manual that includes modbus specification, as well as experimental testing to validate items. Not everything listed here has been validated.
​​
​​Please leave comments if you have questions or see any inaccuracies.

​​Setup

  • ​​PD001: 2 (Source of run commands: communication port)
  • ​​PD002: 2 (Source of operating frequency: communication port)
  • ​​PD163: 1 (Communication address: 1)
  • ​​PD164: 1 (Communication Baud Rate: 9600)
  • ​​PD165: 3 (Communication Data Method: 8N1 RTU)

​​General RTU Protocol

​​
​​[Quiet]
​​(at least 50ms)
​​ADDR
​​FUNC
​​LEN
​​DATA…
​​CRC (2 bytes)
​​[Quiet]
​​(at least 50ms)

​​Function Codes

​​01: Read PD Parameter

​​
​​Command
​​
​​ADDR
​​CMD
​​LEN
​​PAR
​​DATA
​​CRC
​​Description
​​0x01
​​0x01
​​0x03
​​0xA5
​​0x00 0x00
​​0x?? 0x??
​​Read PD165 (165=0xA5)
​​Response
​​Success:
​​Echo of command:
​​ADDR 0x01 LEN PAR Data
​​
​​If DATA is one word, the LEN=3, If DATA is one byte, the LEN=2 (presumably because the parameter code counts as one byte of data in addition to the value which is either 1 or 2 bytes)
​​
​​Failure:
​​When inverter has no this function code or reply no effect, the format as follows:
​​ADDR 0x81 0x01 PAR
​​

​​02: Write PD Parameter

​​
​​Command
​​
​​ADDR
​​CMD
​​LEN
​​PAR
​​DATA
​​CRC
​​Description
​​0x01
​​0x02
​​0x03
​​0x03
​​0x09 0xC4
​​0x?? 0x??
​​Write PD003 (0x9C4 = 2500 = 25.00Hz)
​​ADDR=0 for broadcast, it write to all inverter, but no reply.
​​
​​Response
​​Success:
​​Unspecified
​​
  • ​​test successful response - probably it’s an echo?
​​
​​Failure:
​​When the setting is incorrect or the inverter does not have this function, the format returned is as follows:
​​ADDR 0x81 0x01 PAR
​​
  • ​​check response byte
​​