HTU21D Xplained Pro Datasheet by TE Connectivity Measurement Specialties

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SENSOR SOLUTIONS /// MEAS HTU21D XPLAINED PRO BOARD 062017
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MEAS HTU21D
XPLAINED PRO BOARD
Digital Humidity
Digital Component Sensor (DCS) Development Tools
The HTU21D Xplained Pro provides the necessary hardware to
interface the HTU21D digital relative humidity and temperature sensor
to any system that utilizes Xplained Pro compatible expansion ports
configurable for I2C communication. The HTU21D sensor is a self-
contained humidity and temperature sensor that is fully calibrated
during manufacture. The sensor can operate from 1.5V to 3.6V, has
selectable resolution, low battery detect, and checksum capability. The
HTU21D has a low power stand-by mode for power-sensitive
applications.
Refer to the HTU21D datasheet for detailed information regarding
operation of the IC:
http://www.te.com/usa-en/product-CAT-HSC0004.html
Specifications
Measures relative humidity from 0% to 100%
Measures temperature from -40°C to 125°C
I2C communication
Fully calibrated
Fast response time
Selectable resolution
Very low power consumption
Performance
0% to 100% relative humidity range
-40°C to 125°C temperature range
Very low power consumption
Operates from 1.5V to 3.6V
Fast response time – 5 seconds typical
Built-in heater for fast recovery from saturation
Recovers fully from condensation
Fast conversion time – 14ms typical
Features
20-pin Xplained Pro compatible connector
I2C interface
Xplained Pro Hardware identification Chip
Atmel Studio 6 Project available for download
µC C code available for download
Selectable 8-12 bit resolution for humidity
Selectable 12-14 bit resolution for temperature
Schematic
H H O y ‘8"(30mv‘) ‘.97”(SDr~‘m) A 2 25"(55mm)
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Digital Humidity DCS Development Tools
SENSOR SOLUTIONS /// MEAS HTU21D XPLAINED PRO BOARD 062017
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Connector Pin Assignments (I2C Communications)
System Plug
Dimensions (mm)
Detailed Description
I2C Interface
The peripheral module can interface to the host being plugged directly into an Xplained Pro extension port (configured for I2C)
through connector JP1.
External Control Signals
The IC operates as an I2C slave using the standard 2 wire I2C connection scheme. The IC is controlled either by the host
(through the Xplained Pro connector). In cases where one or more of the SCL and SDA signals are driven from an external
source, 10k resistors R1, R2 provide pull-up. However, this also increases the apparent load to the external driving source. If
the external source is not capable of driving these loads (10k), they should be removed.
Reference Materials
The complete software kit is available for download at: Link to HTU21D_CPROJ.zip
Connector JP1
Pin No.
Signal
Pin No.
Signal
Description
1
ID
11
SDA
TWI Serial Data
2
GND
12
SCL
TWI Serial Clock
3
N/C
13
N/C
Not Connected
4
N/C
14
N/C
Not Connected
5
N/C
15
N/C
Not Connected
6
N/C
16
N/C
Not Connected
7
N/C
17
N/C
Not Connected
8
N/C
18
N/C
Not Connected
9
N/C
19
GND
Ground
10
N/C
20
Vdd
Power Supply
MEAS HTU21D XPLAINED PRO BOARD
Digital Humidity DCS Development Tools
SENSOR SOLUTIONS /// MEAS HTU21D XPLAINED PRO BOARD 062017
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Drivers & Software
Detailed example software and drivers are available that execute directly without modification on a number of development
boards that support an integrated or synthesized microprocessor. The download contains several source files intended to
accelerate customer evaluation and design. The source code is written in standard ANSI C format, and all development
documentation including theory/operation, register description, and function prototypes are documented in the interface file.
Functions Summary
Enumerations
enum
htu21_i2c_master_mode {
htu21_i2c_hold,
htu21_i2c_no_hold
}
enum
htu21_status {
htu21_status_ok, htu21_status_no_i2c_acknowledge,
htu21_status_i2c_transfer_error, htu21_status_crc_error
}
enum
htu21_resolution {
htu21_resolution_t_14b_rh_12b = 0, htu21_resolution_t_12b_rh_8b,
htu21_resolution_t_13b_rh_10b, htu21_resolution_t_11b_rh_11b
}
enum
htu21_battery_status { htu21_battery_ok, htu21_battery_low }
enum
htu21_heater_status { htu21_heater_off, htu21_heater_on }
Functions
void
htu21_init (void)
Configures the SERCOM I2C master to be used with the HTU21 device.
bool
htu21_is_connected (void)
Reset the HTU21 device.
enum htu21_status
htu21_reset (void)
Reset the HTU21 device.
enum htu21_status
htu21_read_serial_number (uint64_t *)
Reads the htu21 serial number.
enum htu21_status
htu21_set_resolution (enum htu21_resolution)
Set temperature and humidity ADC resolution.
void
htu21_set_i2c_master_mode (enum htu21_i2c_master_mode)
Set I2C master mode. This determines whether the program will hold while ADC is accessed or will wait some time.
enum htu21_status
htu21_read_temperature_and_relative_humidity (float *, float *)
Reads the relative humidity value.
enum htu21_status
htu21_get_battery_status (enum htu21_battery_status *)
Provide battery status.
enum htu21_status
htu21_enable_heater (void)
Enable heater.
enum htu21_status
htu21_disable_heater (void)
Disable heater.
enum htu21_status
htu21_get_heater_status (enum htu21_heater_status *)
Get heater status.
float
htu21_compute_compensated_humidity (float, float)
Returns result of compensated humidity.
float
htu21_compute_dew_point (float, float)
Returns the computed dew point.
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Digital Humidity DCS Development Tools
SENSOR SOLUTIONS /// MEAS HTU21D XPLAINED PRO BOARD 062017
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Project Setup
This project is based on ATSAMD20J18 board with Measurement Specialties Xplained Pro extension board connected to
EXT1 pad as shown on figure below.
Running the Application
1. Download the HTU21D Xplained Pro example package on TE Website
2. Decompress the archive file
3. Open the .cproj project file with Atmel Studio 6
4. You will now be able to build the HTU21D example project -
5. Finally, run the build result on your Xplained Pro Board -
Application Code
This section is intended to provide a basic example of functionality.
/**
* \file main.c
*
* \brief HTU21 Temperature & Humidity monitoring application file
*
* Copyright (c) 2014 Measurement Specialties. All rights reserved.
*
*/
#include <asf.h>
uint64_t serial;
float temperature;
float relative_humidity;
float compensated_humidity;
float dew_point;
enum htu21_heater_status heater;
int main (void)
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Digital Humidity DCS Development Tools
SENSOR SOLUTIONS /// MEAS HTU21D XPLAINED PRO BOARD 062017
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{
enum htu21_status status;
float last_temperature = 0;
float variation = 0;
uint8_t n=0;
system_init();
delay_init();
// Configure device and enable
htu21_init();
if( !htu21_is_connected() )
return -1;
// Reset HTU21
status = htu21_reset();
if( status != htu21_status_ok)
return -1;
// Read serial number
status = htu21_read_serial_number(&serial);
if( status != htu21_status_ok)
return -1;
// Configure resolution
status = htu21_set_resolution(htu21_resolution_t_12b_rh_8b);
if( status != htu21_status_ok)
return -1;
// Monitor temperature every 500ms
while (1) {
// Enable heater for 10s
if( (n==10) ) {
status = htu21_enable_heater();
if( status != htu21_status_ok)
return -1;
}
// Disable heater after 20s
if( (n==20) ) {
status = htu21_disable_heater();
if( status != htu21_status_ok)
return -1;
}
// Check heater status
status = htu21_get_heater_status(&heater);
if( status != htu21_status_ok)
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Digital Humidity DCS Development Tools
SENSOR SOLUTIONS /// MEAS HTU21D XPLAINED PRO BOARD 062017
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return -1;
// Alternate between w and w/o hold temperature read
if( n&1 )
htu21_set_i2c_master_mode(htu21_i2c_no_hold);
else
htu21_set_i2c_master_mode(htu21_i2c_hold);
status = htu21_read_temperature_and_relative_humidity(&temperature, &relative_humidity);
if( status != htu21_status_ok)
return -1;
compensated_humidity = htu21_compute_compensated_humidity(temperature,relative_humidity);
dew_point = htu21_compute_dew_point(temperature,relative_humidity);
variation += temperature - last_temperature;
// Look for significant temperature variation
if ( variation >= 0.5 ) {
// Yes, so turn LED on.
port_pin_set_output_level(LED_0_PIN, LED_0_ACTIVE);
variation = 0;
} else if ( variation <= -0.5 ) {
// No, so turn LED off.
port_pin_set_output_level(LED_0_PIN, LED_0_INACTIVE);
variation = 0;
}
delay_ms(500);
last_temperature = temperature;
n++;
if(n==50) n=0;
}
return 0;
}
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MEAS HTU21D XPLAINED PRO BOARD
Digital Humidity DCS Development Tools
SENSOR SOLUTIONS /// MEAS HTU21D XPLAINED PRO BOARD 062017
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Ordering Information
Description
Part Number
MEAS HTU21D XPLAINED PRO BOARD
DPP301A000
PRODUCT SHEET
MEAS France SAS,
a TE Connectivity company.
Tel:+33 (0) 800-440-5100
Email: customercare.tlse@te.com
te.com/sensorsolutions
Measurement Specialties, Inc., a TE Connectivity company.
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products and/or company names referred to herein might be trademarks of their respective owners.
The information given herein, including drawings, illustrations and schematics which are intended for illustration purposes
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