SMD500 Datasheet, PDF (8/10 Pages) List of Unclassifed Manufacturers – Altimeter / Barometer Module ultra low power, low voltage

4.3 Starting temperature and pressure measurement
Figure 6 and 7 show the timing diagrams to start the measurement of the temperature value UT and pressure value UP. After
start condition the master sends the module address write, the register address and the control register. The SMD500 sends an
acknowledgement (ACKS) every 8 data bits when data is received. The master sends a stop condition after the last ACKS.
Clock Frequency selection:
Bit 2 of the control register selects the master clock prescaler, see table 4. When the bit is low, the external clock signal
32768 kHz is divided by two and the internal frequency will be 16384 Hz. If the master clock selection bit is high, the external
clock 1 MHz is divided by 64 and the internal clock frequency will be 15625 Hz. The conversion times for external clock 1 MHz
and 32768 Hz are about 34 ms for the pressure measurement and for temperature measurement.
SCL
SDA
Module address
write 0xEE
Register address
0xF4
Control register
0xEE or 0xEA
S
ACKS
ACKS
ACKS P
Figure 6: Timing diagram for starting temperature measurement
SCL
SDA
Module address
write 0xEE
Register address
0xF4
Control register
0xF4 or 0xF0
S
ACKS
ACKS
ACKS P
Figure 7: Timing diagram for starting pressure measurement
Abbreviations:
S
P
ACKS
ACKM
NACKM
Start
Stop
Acknowledge by Slave
Acknowledge by Master
Not Acknowledge by Master
Table 4: Control register values
measurement
temperature
pressure
Master cock
32.768 kHz
1 MHz
32.768 kHz
1 MHz
control register value
0xEE
0xEA
0xF4
0xF0
conversion time
34 ms
35 ms
34 ms
35 ms
8
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