Vaisala GMP231 - Manual (Page 63)

Chapter 5 _______________________________________________________________ I2C Interface
VAISALA ________________________________________________________________________ 61
Set_Parameter
Set_Parameter command (ID 82h) writes parameter values to non-
volatile memory. You can use it to set the operational parameters of the
GMP231. Depending on the change, the functionality of the GMP231
may not change immediately.
The length of the invoke message varies depending on the data length.
The master must write as many bytes as indicated in the frame length of
the invoke message. If the master tries to write a longer or shorter
message, GMP231 rejects the message.
Table 25 Set_Parameter Invoke Message
Message Segment Length Content
I
2
C address 1 byte I
2
C address (write)
Command ID 1 byte Always 82h
Device address 1 byte See Table 13 on page 51
Frame length 1 byte Varies according to data length,
07h ... 38h.
Data 1 byte Parameter ID
1 ... 50 bytes Parameter value
Checksum 2 bytes See section Checksum on page 56
Table 26
Set_Parameter Response Message
Message Segment Length Content
I
2
C address 1 byte I
2
C address (read)
Status 1 byte See section Status Byte on page 56.
Command ID 1 byte Always 82h
Device address 1 byte See Table 13 on page 51
Frame length 1 byte Always 08h.
Data 1 byte Parameter ID
1 byte Return code. See Table 27 below.
Checksum 2 bytes See section Checksum on page 56
Table 27
Set_Parameter Return Codes
Code Meaning
0
Ok
1 Unknown parameter ID
2 Not writeable parameter
3 Value field too long
4 Value field too short
5 Data value not accepted