SHT35 datasheet(12/20 Pages) ETC2

12 / 20 page

Datasheet SHT3x-DIS

www.sensirion.com

August 2016 - Version 3

12/20

Interface Reset

If communication with the device is lost, the following

signal sequence will resetthe serial interface:While

leaving SDA high,toggle SCL nine or more times.This

mustbe followed by a Transmission Start sequence

preceding the nextcommand.This sequence resets the

interface only. The status register preserves its content.

Soft Reset / Re-Initialization

The SHT3x-DIS provides a soft reset mechanism that

forces the system into a well-defined state without

removing the power supply. When the system is in idle

state the soft reset command can be sentto the SHT3x-

DIS. This triggers the sensor to reset its system

controller and reloads calibration data from the memory.

In order to start the soft reset procedure the command

as shown in Table 13 should be sent.

It is worth noting that the sensor reloads calibration data

prior to every measurementby default.

Command

Hex Code

Soft Reset

0x30A2

Table 13 Soft reset command (Clear blocks are controlled

by the microcontroller, grey blocks by the sensor).

Reset through General Call

Additionally, a reset of the sensor can also be generated

using the “general call” mode according to I2C-bus

specification12. This generates a reset which is

functionally identical to using the nReset pin. It is

important to understand that a reset generated in this

way is not device specific. All devices on the same I2C

bus that support the general call mode will perform a

reset. Additionally, this command only works when the

sensor is able to process I2C commands. The

appropriate command consists of two bytes and is

shown in Table 14.

Reset through the nReset Pin

Pulling the nReset pin low (see Table 6) generates a

reset similar to a hard reset. The nResetpin is internally

connected to VDD through a pull-up resistor and hence

active low. The nReset pin has to be pulled low for a

minimum of 1 µs to generate a reset of the sensor.

Command

Code

Address byte

0x00

Second byte

0x06

Reset command using the

general call address

0x0006

Table 14 Reset through the general call address (Clear

blocks are controlled by the microcontroller, grey blocks by

the sensor).

Hard Reset

A hard reset is achieved by switching the supply voltage

to the VDD Pin off and then on again.In order to prevent

powering the sensor over the ESD diodes,the voltage to

pins 1 (SDA), 4 (SCL) and 2 (ADDR) also needs to be

removed.

4.10 Heater

The heater can be switched on and offbycommand,see

table below. The status is listed in the status register.

After a reset the heater is disabled (defaultcondition).

Command

Hex Code

MSB

LSB

Heater Enable

0x30

Heater Disabled

Table 15 Heater command (Clear blocks are controlled by

the microcontroller, grey blocks by the sensor).

4.11 Status Register

The status register contains information on the

operational status of the heater, the alert mode and on

the execution status of the last command and the last

write sequence. The command to read out the status

the contentcan be found in Table 17.

S General Call Address

Reset Command

General Call 1st byte

General Call 2nd byte

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