HS300x Datasheet

© 2020 Renesas Electronics Corporation

12

April 22, 2020

6.6 Data Fetch (DF)

At the end of a measurement cycle, valid data can be fetched. The status bits of the DF results can be used to detect if the data is valid or stale

(see section 6.7); otherwise, wait for the measurements to complete before performing the DF.

The DF command starts with the 7-bit slave address followed by an eighth bit = 1 (READ). The HS300x as a slave sends an acknowledge

(ACK) indicating success.

The number of data bytes returned by the HS300x is determined by when the master sends the NACK and STOP condition. The full 14 bits of

the humidity data are fetched in the first two bytes. The two MSBs of the first byte are the status bits.

The 14 bits of temperature data follow the humidity data. The last two bits (LSBs) of the fourth data byte are undetermined and should be

masked off. In the event that the temperature data is not needed, the read can be terminated by sending a NACK after the second byte.

followed by a stop bit. The measurement time depends on the configured sensor resolution. The table below lists examples when the resolutions

for the relative humidity and temperature measurements are the same. For different relative humidity and temperature resolution settings, the

measurement times in 3 should be used, along with the 0.1 ms wake-up time.

For example, an 8-bit relative humidity measurement and a 12-bit temperature measurement results in a total measurement time of:

0.1 ms + 0.55 ms + 4.5 ms = 5.15 ms.

RH+T measurement times (including wake-up time) at different resolution settings.

(bits)

Measurement

time (ms)

8

1.20

10

2.72

12

9.10

14

33.90

1

Same resolutions are assumed for both relative humidity and temperature.

Figure 17.

Data Fetch

Device Slave Address [6:0]

Humidity Data [13:8]

Humidity Data [7:0]

Humidity Data [13:8]

Humidity Data [7:0]

Temp. Data [15:8]

Slave Address Bit (MSB first)

Commandor Data Bit (Example: Bit 2)

Status Bit

Start Condition

Stop Condition

Acknowledge (ACK)

Not Acknowledge

Read/Write

(NACK)

(Read = 1)

S

S

R

N

Wait for

Slave ACK

Master ACK

Master ACK

Master NACK

14 13

11

12

10

8

9

A

6 5

7

3

4

2

N

1 0

S

1

S

0 0

1

0

0

R

(1)

0

A 15

1

S

0

1 0

R

(1)

0

A

14 13

15

11

12

10

8

9

A

6 5

7

3

4

2

A

1 0

14 13

15

11

12

10

A

9 8

0

0

Device Slave Address [6:0]

A

2

Temp. Data [7:2]

6 5

7

3

4

2

S

N

1 0

Mask [1:0]