Data Sheet
15
www.epluse.comv1.3 / Modification rights reserved
HTE501
In case a command without clock stretching has been issued, the slave does not acknowledge (NACK) a
read header as long as the calculation has not been finished:
I²C
Datenstruktur
7654321 76543210 76543210 7654321
S
W
0
A
0
A
0
A
0
PS
R
1
Without clock stretching
7654321
N
1
PS
R
1
A
0
With clock stretching
A
0
P
Next for both
76543210 76543210 76543210
A
0
A
0
A
0
76543210 76543210 76543210
A
0
A
0
N
1
P
!
R / W
R / W
!
R / W
!
I2C-ADDRESS
CMD MSB
NEXT1
NEXT2
1
I2C-ADDRESS
I2C-ADDRESS
SCL FREE FOR OTHER BUS MEMBERS
MEASUREMENT ONGOING
t
MEAS
MEASUREMENT FINISHED
NEXT2
1
SCL PULLED LOW
TEMPERATURE MSB
2
TEMPERATURE LSB CRC8
NEXT3
HUMIDITY MSB
3
HUMIDITY LSB CRC8
16 BIT COMMAND
CMD LSB
MEASUREMENT ONGOING
t
MEAS
ASTRID_I2C_Befehle_version2 - Kopie / 0x2C06_0x241D 19.10.2021 \ Haider A.
Figure 12: Poll for meauring values until ACK
After the calculation is finished, the slave responds to a read header with a pair of data words, each of
them is followed by an 8 bit checksum (CRC8). The first data word contains the temperature value while
the second word contains the relative humidity value. The master has to acknowledge each single data
byte by an acknowledge (ACK), otherwise the slave will stop sending any further data and wait for a stop
condition (P):
I²C
Datenstruktur
7654321 76543210 76543210 7654321
S
W
0
A
0
A
0
A
0
PS
R
1
Without clock stretching
7654321
N
1
PS
R
1
A
0
With clock stretching
A
0
P
Next for both
76543210 76543210 76543210
A
0
A
0
A
0
76543210 76543210 76543210
A
0
A
0
N
1
P
!
R / W
R / W
!
R / W
!
I2C-ADDRESS
CMD MSB
NEXT1
NEXT2
1
I2C-ADDRESS
I2C-ADDRESS
SCL FREE FOR OTHER BUS MEMBERS
MEASUREMENT ONGOING
t
MEAS
MEASUREMENT FINISHED
NEXT2
1
SCL PULLED LOW
TEMPERATURE MSB
2
TEMPERATURE LSB CRC8
NEXT3
HUMIDITY MSB
3
HUMIDITY LSB CRC8
16 BIT COMMAND
CMD LSB
MEASUREMENT ONGOING
t
MEAS
ASTRID_I2C_Befehle_version2 - Kopie / 0x2C06_0x241D 19.10.2021 \ Haider A.
Figure 13: Measured value readout
6.5 Periodic Measurement (0x201E)
Once issued, measurements and calculations are started automatically with a given measuring interval and
resolution.
The standard measurement interval is 1s and the resolution is 13 bit for RH and T. If necessary the
measurement frequency and the measurement resolution can be changed (see chapter 6.13).
This mode does not support clock stretching.
Command CMD Hex Code
Periodic measurement 201E
I²C
Datenstruktur
7654321 76543210 76543210
S
W
0
A
0
A
0
A
0
P
R / W
I2C ADDRESS
CMD MSB
16 BIT COMMAND
CMD LSB
ASTRID_I2C_Befehle_version2 - Kopie / 0x2024_0x2737 20.09.2021 \ Haider A.
Figure 14: Periodic measurement commands
A periodic measurement command with a different measurement interval / resolution can be issued at any
time, but the calculated value will be updated according the new settings earliest after a measurement with
the new settings has been performed. Please refer to Chapter 6.13.