Vaisala GMP231 - Manual (Page 53)

Chapter 5 _______________________________________________________________ I2C Interface
VAISALA ________________________________________________________________________ 51
Communication Parameters
GMP231 supports maximum 50 kHz clock speed. Protocol bits are sent
most significant bit (MSB) first. Parameter bytes are sent using little
endian order.
Addressing
GMP231 uses 7-bit addressing. The address consists of:
- 4-bit device type identifier part (default “0001” for GMP231)
- 3-bit sub address (default “001”)
The full 7-bit default address is “0001001” (09h). In I
2
C communication,
the address should be provided by the master in the standard way after
the I
2
C start condition, with the read/write bit as the least significant bit
(LSB).
Table 12 GMP231 I
2
C Address
0 0 0 1 0 0 1 R/W
Device type Sub-address Read/write bit
(LSB)
The I
2
C implementation of the GMP231 also includes the address inside
the message frame. The purpose of this is to make the I
2
C
implementation easier, since the I
2
C address can be lost by the I
2
C
hardware. This address is provided without the read/write bit, with zero
as the MSB.
Table 13 GMP231 Device Address
0 0 0 0 1 0 0 1
MSB Device type Sub-address
NOTE Make sure there are no addressing conflicts if other I
2
C devices are put
on the same bus. The GMP231 address can be changed, see Table 40 on
page 67.