HTU21P Ver la hoja de datos (PDF) - Unspecified
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HTU21P Datasheet PDF : 21 Pages
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HTU21D(F) Sensor
Digital Relative Humidity sensor with Temperature output
Timing diagram for digital input/output pads
DATA directions are seen from the HTU21D(F) sensor. DATA line in bold is controlled by the sensor.
DATA valid read time is triggered by falling edge of anterior toggle.
COMMUNICATION PROTOCOL WITH HTU21D(F) SENSOR
Start-up sensor
The HTU21D(F) sensor requires a voltage supply between 1.5V and 3.6V. After power up, the device needs at
most 15ms while SCK is high for reaching idle state (sleep mode), i.e to be ready accepting commands from the
MCU. No command should be sent before that time. Soft reset is recommended at start, refer p.11.
Start sequence (S)
To initiate transmission, a start bit has to be issued. It consists of a lowering of the DATA line
while SCK is high followed by lowering SCK.
Stop sequence (P)
To stop transmission, a stop bit has to be issued. It consists of a heightening of the DATA line
while SCK is high preceded by a heightening of the SCK.
HTU21D(F) SENSOR LIST OF COMMANDS AND REGISTER ADRESSES
For sample source code, please request to humidity.application@meas-spec.com.
Sending a command
After sending the start condition, the subsequent I²C header consist of a 7-bit I²C device address 0x40 and a
DATA direction bit (‘0’ for Write access : 0x80). The HTU21D(F) sensor indicates the proper reception of a byte
by pulling the DATA pin low (ACK bit) after the falling edge of the 8th SCK clock. After the issue of a
measurement command (0xE3 for temperature, 0xE5 for relative humidity), the MCU must wait for the
measurement to complete. The basic commands are given in the table below:
HPC199_3 HTU21D(F) Sensor Datasheet
www.meas-spec.com
10/21
October 2013
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