HS401x Datasheet

R36DS0023EU0103 Rev.1.03

Jun 6, 2022

Page 14

Figure 16. Sequence to Retrieve the Latest Results in Periodic Measurement Mode

The frequency of the periodic measurements can be set using the configuration registers. Section 4.7 describes

how these registers are accessed, and section 4.8.2 provides the register settings needed to configure and

activate the periodic measurements.

When the periodic measurement mode is active, the only commands the chip will respond to are the data fetch

command, and a command to stop the periodic measurements. The command to stop periodic measurements is

commands.

Figure 17. Sequence to Stop Periodic Measurements

4.6

Alert Feature

The HS401x sensors have an optional Alert feature that can be configured in two ways as follows:

1.

The Alert pin can be used to indicate when a measurement is active in Periodic Measurement Mode. This is

the default behavior of the Alert pin upon power-up.

2.

The Alert pin can be used to trigger an interrupt on the system microcontroller so an appropriate action can

be taken if the temperature or humidity is outside of the desired limits.

These features are described in the following two sub-sections.

4.6.1.

Alert Pin – Measurement Active

The default behavior of the Alert pin is to indicate when a measurement is active if Periodic Measurement Mode

is used. Upon power-up, the Alert pin will have a logic high level. When periodic measurement mode is

activated, the Alert pin will have a logic low level between measurements and a logic high during measurements.

This behavior is shown in Figure 18, and the Alert pin will exhibit this functionality when the temperature and

humidity alerts are disabled (see Table 11).

If Periodic Measurement Mode is not active, the Alert pin will remain at a logic high level.

0

1

0

1

0

0

0

ACK

0

0

1

1

0

0

0

0

ACK P

I2C Address (7 bits) + write bit

Stop Periodic Meas. Command (0x30)