Hope RF
HP01-TQ
BAROMETER MODULE
2010-6-3
PRELIMINARY
Version: 2.1
. Integrated pressure sensor
. Pressure Range 750-1100hpa
. 16 Bit
ADC
. I
2
C Serial Interface
. One system clock line (32768Hz)
. Low voltage, low power
Description
The HP01 pressure module includes a piezo-resistive pressure sensor and an ADC
interface. It provides 16 bit word data for pressure and temperature related voltage. HP01
is a low power, low voltage device with automatic power down switching. I
2
C Serial
Interface is used for communications with a microprocessor.
Features
. 14 Bit ENOB ADC resolution
. Supply voltage 2.2-3.6v
. -40C to + 85C operating range
Applications
. Pressure measurement and control systems
. Weather forecast products
Block Diagram
1
Hope RF
HP01-TQ
BAROMETER MODULE
2010-6-3
PRELIMINARY
Version: 2.1
Pin Name
VSS
VDD
MCLK
XCLR*
SDA
SCL
Pin Number
1
2
3
4
5
6
Type
G
P
I
I
I/O
I
Function
power ground
power VCC
master clock(32k) input
ADC reset inpu
. I²C data input and output
I
2
C clock input
* XCLR is to reset the AD converter (active low). During the AD conversion phase, XCLR should stay
high. After AD conversion end, keep XCLR pin low before another AD conversion starts.
Absolute Maximum Ratings
Parameter
Supply Voltage
Over pressure
Storage Temperature
Symbol
VDD
P
Tstg
Min
-0.3
-40
Max
4.0
5
125
Unit
V
Bar(abs)
C
Recommended Operating Conditions
Parameter
Supply Voltage
Supply Current
During conversion
Stand by
Operating Pressure Range
Operating Temperature Range
Conversion Time
Duty Cycle of MCLK
Serial Date Rate
P
T
T
SCL
MCLK=32k
40%
50%
900
-40
25
Symbol
VDD
I
Conditions
VDD=3V
500
1
1100
85
35
60%
100
Min
2.2
Typ
3
Max
3.6
Unit
V
V
Hpa (abs)
C
ms
%
KHZ
Pressure and Temperature Output Characteristics
HP01 system is able to reach the following characteristics:
Parameter
Resolution
Accuracy
Pressure Sensitivity
Maximum Error Over Temperature
Long Term Stability
VDD Dependency
Temperature coefficient of sensitivity
TCS
Symbol
Conditions
900-1100
SNS
900-1100
0~+55
12 month
2.0~5.0
Min
0.1
-8
25
-5.0
-1.5
-0.45
1
0
-0.55
Typ
Max
+10
27
30
5.0
1.5
-0.6
Unit
hpa
hpa
Cnts/mbar
hpa
hpa
hpa
∆D1∆D2
2
Hope RF
HP01-TQ
BAROMETER MODULE
2010-6-3
PRELIMINARY
Version: 2.1
Pressure Measurement
The main function of HP01 system is to convert the uncompensated pressure and
temperature signal from a pressure sensor. After the conversion, the following two values
can be obtained:
. measured temperature
“D2”
. measured pressure
“D1”
As the sensor is strongly temperature dependent, it is necessary to compensate for these
effects. Therefore necessary temperature compensation is needed to achieve nominal
accuracy.
Pressure and Temperature Compensation Calculation:
The following information is just a guide line for temperature
compensate, the end user of this module should not be confined
to this method. Many other methods can be deployed to achieve
best accuracy.
Step 1: (set relative pressure starting reference point, normally this step be done after
power up or reset relative pressure)
P0=1013.2hp
D1(P0)=D1
D2(P0)=D2
Step 2: (normal pressure calculation with first order temperature compensation)
dUT=D2-D2(P0)
dTCS=TCS*dUT
dUP=D1-dTCS-D1(P0)
P2=dUP/SNS
P=P0+P2
Example:
D1(P0)=30000
D2(P0)=4100
TCS=-0.55
SNS=27
D1=30036
D2=4107
(obtained after power up reading: D1)
(obtained after power up reading: D2)
(nominal module value from this data sheet)
(nominal module value from this data sheet)
(current pressure AD reading from module)
(current temperature AD reading from module)
; calculate current temperature difference with reference temperature
; calculate compensated pressure offset with temperature coefficients
;
calculate temperature compensated pressure reading
; calculate pressure difference referred to starting pressure P0
; calculate current relative pressure
dUT = 4107-4100 = 7
dTCS=-0.55*7=-3.85
dUP=30036+3.85-30000=39
3
Hope RF
HP01-TQ
BAROMETER MODULE
2010-6-3
PRELIMINARY
Version: 2.1
P2=39/27=1.44
P=1013.2+1.44=1014.6
Serial Interface
The I
2
C interface is used for reading measurement result from AD conversion:D1 and D2.
Reading Temperature and Pressure value:D1,D2
AD chip I
2
C address is set to 0xEE (device write address), 0xEF (device read
address). In order to get the AD value D1 and D2, you have to follow the following
timing sequence:
Pressure Measure:
S 11101110
A
11111111
A
11110000
A
P D S 11101110
A
11111101
A
S 11101111
A
MSB
A
LSB
N P
Select pressure measurement
Temperature Measure:
Read AD value back
S 11101110
A
11111111
A
11101000
A
P D S 11101110
A
11111101
A
S 11101111
A
MSB
A
LSB
N P
Select temperature measurement
Read AD value back
S: I
2
C bus START (refer to AT24C02 EEPROM start command)
P: I
2
C bus STOP (refer to AT24C02 EEPROM stop command)
A (bold):
I
2
C bus acknowledge by slave (SDA pull low: slave send out bit 0)
A: I
2
C bus acknowledge by master (SDA pull low: master send out bit 0)
N: I
2
C bus no acknowledge from master (SDA keep high: master send out bit 1 instead)
D : delay for 38ms or above
MSB: conversion result (MSB bit clocked out first)
LSB: conversion result (MSB bit clocked out first).
Remark:
Before start an AD conversion cycle, remember to set XCLR pin high so that the system
is no longer in the reset state (not valid for HP01).
4
Hope RF
HP01-TQ
BAROMETER MODULE
2010-6-3
PRELIMINARY
Version: 2.1
All data read from the module is in hex format.
After first power on, the first read data should be disregarded, and only the second value
be used. This can assure that unstable reading after power on reset can be filtered out.
Like any other semiconductor device, the sensor is sensitive to light. During the
application of this sensor, please keep the sensor in dark place to achieve best accuracy.
Since the module is not calibrated for sensitivity and temperature, thus only relative pressure can be
calculated. If you need higher accuracy with temperature, please refer to our HP02 or HP03 series
pressure module accordingly.
Typical Application Circuit Diagram:
5
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