HDC1008_15 Datasheet, PDF (12/30 Pages) Texas Instruments – HDC1008 Low Power, High Accuracy Digital Humidity Sensor with Temperature Sensor

HDC1008
SNAS649A – OCTOBER 2014 – REVISED NOVEMBER 2014
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4. Read the output data:
Read the temperature data from register address 0x00, followed by the humidity data from register address
0x01 in a single transaction as shown in Figure 14. A read operation will return a NACK if the contents of the
registers have not been updated as shown in Figure 13.
To perform another acquisition with the same measurement configuration simply repeat steps 2 through 4.
If only a humidity or temperature measurement is desired, the following steps will perform a measurement and
retrieve the result:
1. Configure the acquisition parameters in register address 0x02:
(a) Set the acquisition mode to independently measure temperature or humidity by setting Bit[12] to 0.
(b) For a temperature measurement, set the desired temperature measurement resolution:
– Set Bit[10] to 0 for 14 bit resolution.
– Set Bit[10] to 1 for 11 bit resolution.
(c) For a humidity measurement, set the desired humidity measurement resolution:
– Set Bit[9:8] to 00 for 14 bit resolution.
– Set Bit[9:8] to 01 for 11 bit resolution.
– Set Bit[9:8] to 10 for 8 bit resolution.
2. Trigger the measurement by executing a pointer write transaction. Refer to Figure 12.
– Set the address pointer to 0x00 for a temperature measurement.
– Set the address pointer to 0x01 for a humidity measurement.
3. Wait for the measurement to complete, based on the conversion time (refer to Electrical Characteristics for
the conversion time). Alternatively, wait for the assertion of DRDYn.
4. Read the output data:
Retrieve the completed measurement result from register address 0x00 or 0x01, as appropriate, as shown in
Figure 10. A read operation will return a NACK if the measurement result is not yet available, as shown in
Figure 13.
To perform another acquisition with the same measurement configuration repeat steps 2 through 4.
It is possible to read the output registers (addresses 0x00 and 0x01) during an Temperature or Relative Humidity
measurement without affecting any ongoing measurement. Note that a write to address 0x00 or 0x01 while a
measurement is ongoing will abort the ongoing measurement. If the newest acquired measurement is not read,
DRDYn stays low until the next measurement is triggered.
1
91
9
SCL
SDA
A6 A5 A4 A3 A2 A1 A0 R/W
P7 P6 P5 P4 P3 P2 P1 P0
Start by
Master
Frame 1
7-bit Serial Bus Address Byte
Ack by
Slave
Frame 2
Pointer Register Byte
Ack by
Slave
Figure 12. Trigger Humidity/Temperature Measurement
1
9
SCL
SDA
A6
Start by
Master
A5 A4 A3 A2 A1 A0 R/W
Nack by
Slave
Frame 3
7-bit Serial Bus Address Byte
Figure 13. Read Humidity/Temperature Measurement (Data Not Ready)
12
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