PNI RM3100 Sensor Suite - Manual (Page 36)

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RM3100 & RM2100 Sensor Suite User Manual Page 35 of 45
5.4 Confirm New Data Ready
There are several ways to determine if a measurement has been completed and data is
available in the Measurement Results Registers. One method is monitoring the DRDY line
for it to go HIGH. Recall that for continuous measurement mode, the DRDM bits of the
Continuous Measurement Command byte establish the conditions for DRDY to go HIGH.
Another option when using the SPI interface is monitoring the MISO pin for it to go HIGH.
(The MISO pin is unavailable when using the I
2
C interface, as it is used to set the slave
address of the device.) Another option is to read from the STATUS register, as discussed
below. Only one method need be used.
5.4.1 STATUS Register (0x34)
To read the Status Register, first send a read command to the STATUS register, 0xB4.
The return byte provides the contents of the Status Register:
Bit # 7 6 5 4 3 2 1 0
Value DRDY - - - - - - -
Bit 7 will be HIGH if data is available and LOW if it is unavailable. Bits 0 – 6 are
indeterminate and should be ignored.
5.5 Read the Measurement Results
Each sensor reading consists of 3 bytes of data which are stored in 2’s complement format
(range: -8388608 to 8388607) in the Results Registers within the MagI2C. These registers
are read by sending the Read Results byte, as defined below, where the values of A, B, C,
and D establish the register to be addressed, as given in Table 5-8.
Bit # 7 6 5 4 3 2 1 0
Value 1 0 1 0 A B C D