ML610Q400 Series Sample Program AP Notes For Humidity

SQ003104E008
ML610Q400 Series
Sample Program AP Notes
For
Humidity Calculation Module
2nd edition
Issue Date : January 27, 2010
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Contents
1.
OVERVIEW............................................................................................................................................ 1
2.
HUMIDITY CALCULATION MODULE .............................................................................................. 2
2.1.
2.2.
2.3.
2.4.
2.5.
2.6.
3.
FUNCTION OVERVIEW ......................................................................................................................... 8
OPERATING CONDITIONS ..................................................................................................................... 8
SAMPLE PROGRAM .............................................................................................................................. 9
FLOWCHART OF HUMIDITY CALCULATION ..........................................................................................11
TYPICAL PERIPHERAL CIRCUIT DIAGRAM ......................................................................................... 12
HOW TO PREPARE THE HUMIDITY RATIO - HUMIDITY CONVERSION TABLE ....................................... 13
CELSIUS FAHRENHEIT CONVERSION MODULE........................................................................ 16
3.1.
3.2.
FUNCTION OVERVIEW ........................................................................................................................
16
OPERATION CONDITION .................................................................................................................... 16
i
1.
Overview
This document describes the application programming notes (hereafter called the AP notes) arranged to help customers
develop software that, by using the RC-ADC, which is hardware that the ML610Q400 Series MCU (hereafter called the
MCU) has, performs humidity sensor measurements.
APIs are provided for each function module. The AP notes describe the functions and operating conditions of each API
and samples of use of those APIs.
In connection with the AP notes, a sample program is provided that actually operates using APIs. on ML610Q400
Series Demo Kit.
* This AP note also describes about “Celsius Fahrenheit conversion module” that is included in the sample program in
the section 3.
Related Documents
The following are the related documents. Read them as required.
ML610Q400 Series Sample Program AP Notes For Sensor/Mesurement Application
ML610Q400 Series Sample Program API Manual
ML610Q431/ML610Q432 User’s Manual
ML610Q411/ML610Q412/ML610Q415 User’s Manual
ML610Q421/ML610Q422 User’s Manual
ML610Q482 User’s Manual
ML610Q400 Series Demo Kit Hardware User’s Manual
nX-U8/100 Core Instruction Manual
MACU8 Assembler Package User’s Manual
CCU8 User’s Manual
CCU8 Programming Guide
CCU8 Language Reference
DTU8 User’s Manual
IDEU8 User’s Manual
uEASE User’s Manual
uEASE Connection Manual ML610Qxxx
FWuEASE Flash Writer Host Program User’s Manual
LCD Image Tool User’s Manual
1
2.
Humidity calculation module
Humidity is measured from the resistor value of humidity sensor. The variable band of resistance value is from several
hundred ohm to several mega ohm. Therefore, to fix measurement time, use Resistance Measurement Method 1(*).
And humidity sensor has the temperature characteristics like the figure below. By making use of this characteristics,
calculate humidity. First, calculate humidity of 25 degrees centigrade as base, second revise humidity using current
temperature.
(*) For detailed description, refer “ML610Q400 Series Sample Program AP Notes For Sensor/Mesurement
Application”, topic ‘How to Measure Resistance Value’ of chapter 3.2 RC-ADC Control Module.
100000
Resistance (K ohm)
10000
1000
25°C
5°C
45°C
100
10
1
0
20
40
60
80
100
Relative Humidity (%RH)
Figure 2-1 The characteristic graph for resistance – humidity (C10-M53R, Shinyei Technology)
2
%rh
0°C
5°C
10°C
15°C
20°C
25°C
30°C
35°C
40°C
45°C
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
38000
14000
5012
2017
1014
544
313
183
104
63.8
38
23.5
15.8
10.6
7.41
5.3
24000
8619
3367
1469
751
406
230
139
80.2
49.3
29.9
18.4
12.3
8.32
5.49
4
14000
5821
2251
1076
583
320
183
111
62.5
37.8
23.8
15.3
10.2
6.89
4.85
3.5
8664
3870
1615
815
437
246
142
86.3
50.4
30.5
18.9
12.3
8.21
5.55
4.1
3
5549
2500
1248
649
352
191
112
66.2
39.2
24.3
15.4
10.3
7.18
4.82
3.37
2.5
3900
1880
960
495
270
150
87
50.2
31
19.8
13
8.65
5.8
4
2.9
2.11
2920
1401
734
380
213
121
68.7
40.1
24.9
16.2
10.5
7.42
5.09
3.49
2.57
1.9
2203
1126
579
322
177
98
55.9
33.8
19.9
13.2
9.04
6.37
4.35
3.09
2.26
1.7
1760
852
461
247
135
77.4
44.8
27.6
17.5
11.7
8.04
5.74
3.93
2.8
2.04
1.5
1304
699
353
193
108
63.8
37.8
24.5
15
10.2
7.03
5
3.42
2.41
1.8
1.35
* The data in the shade field is not a standard data.
Figure 2-2
The characteristic table for resistance – humidity (C10-M53R, Shinyei Technology)
3
50°C
1098
571
294
160
87.5
49.9
30.7
19.8
13
8.8
6.01
4.26
3.02
2.1
1.55
1.17
Unit：Kohm
First, the measured humidity range, the desired resolution, and the measured state need to be determined. They must
be determined by taking the functions and specification of the product that uses the MCU into account. When these
are determined, the value of humidity sensor Rh, connected to the microcomputer, the reference resistor Rs and the
reference capacitor Cs must be determined. Select a humidity sensor by taking its characteristics and the used
environments into account.
The value of Rs is defined by the humidity sensor. In this case of the humidity sensor which the sample program uses,
the value of Rs is 150Kohm. For more detail, please see the section “2.6.1. Selection of the reference registor”.
You must select enough capacity to gain the required oscillation frequenceis by CR oscillation.
Select Rh, Rs and Cs so that the oscillation frequencies within the measured temperature range can be measured within
the specification of the RC-ADC of the MCU. For instance, the following setting is acceptable:
If VDD = 3 V and Cs = 820 pF, Rh must be 1 kΩ or more.
If VDD = 1.5 V and Cs = 820 pF, Rh must be 2 K or more.
For detailed description, refer the chapter “RC Oscillation Type A/D Converter” of the User’s Manual for your
target MCU.
Next, make the conversion table between humidity and humidity-ratio.This humidity-ratio is the ratio of the below two
counter value.
a) The number of counter which is gained by the RC oscillation between Rt(humidity sensor) and Cs within base
time(This sample program uses 500ms.
b) The number of counter which is gained by RC oscillation between Rs(Base side) and Cs within same base time.
Define each symbol is as follows:
Rh:
the resistor of humidity sensor
H:
Humidity
frclk: the oscillation frequency by CR oscillation between Rh and Cs
fsclk: the oscillation frequency by CR oscillation between Rs and Cs.
Humidity-ratio (H-ratio) can calculate by frclk/fsclk.
Note:
This sample program multiplies the humidity-ratio by 1024 because of the calculation by an integer.
(If the humidity-ratio is 1024, the humidity is 50% at 25 degrees centigrade because the oscillation frequency of Rh is
equivalent to Rs)
The humidity changes by the temperature. For example, although if the humidity-ratio is 1024 at 25 degrees centigrade,
the humidity will be 45%, if the temperature is 45 degrees centigrade, the humidity will be approximately 36%.
Similarly, if the temperature is 5 degrees centigrade, the humidity will be 54%.
This sample program calculate the humidity by the below procedure.
1 Find the humidity of 25 degrees centigrade.
2 If current temperature is lower than 25 degrees centigrade, find the humidity of 5 degrees centigrade.
3 If current temperature is 25 degrees centigrade or higher, find the humidity of 45 degrees centigrade.
4 The difference between the humidity of 5 or 45 degrees centigrade and the humidity of 25 degrees centigrade
divided 20 makes the humidity per 1 degree centigrade.
5 Find current humidity by the below calculation.
Current humidity = the humidity of 25 degrees + (the difference between current temperature and 25 degrees
centigrade * humidity per 1 degree centigrade)
4
Resistor(Rt)
Resistor(Rh)
Humidity(H)
Characteristic of H－Hratio
Fig2-3 How to make the characteristic of H-rasio - H
From the Rh-H characteristics, resistance r1 for h1 is obtained. Next, from the Rh– H-rasio characteristics, find n1 (n1
= base count value (@150Kohm)/the count value for r1 * 1024) Similarly, n2 and n3 for h2 and h3, respectively, can be
obtained.
The humidity(H)– Humidity ratio (H-ratio) characteristics can be then obtained using the above information.
Repeat the above procedure, make the humidity raito table of 25 degrees centigrade, the upper limit table and lower
limit table of temperature where the revised calculation is needed. This sample program is using the table for 5 degrees
centigrade and 45 degrees centigrade.
5
The H-ratio – H characteristics are converted to multiple linear approximation formulas. Moreover store multiple linear
approximation formulas to revise humidity at 25 degrees centigrade by temperature in the program. The
approximation formula can be made by considering the following:
1 The maximum error between the linear approximation and the actual characteristics must be smaller than the
desired accuracy.
2 The slope of the linear approximation must be less than the desired maximum resolution of temperatures.
3 The linear approximation must be stored within the program area.
The following are examples of linear approximation.
The H– H-ratio characteristics are divided into several intervals (4 portions in this example).
Draw a straight line in each interval as a linear approximation. Linear approximations can be expressed by the
following:
Approximation characteristics of
H – H-ratio
Humidity
Humidity
Characteristics of
h5
h4
H – H-ratio
h5
h4
h3
h3
h2
h2
h1
h1
H25 = a45×(H-ratio – n4) + h4
H25 = a34×(H-ratio – n3) + h3
n1 n2
n3
n4
n5
H-ratio
H25 = a23×(H-ratio – n2) + h2
n1 n2
n3
n4
n5
H-ratio
An enlarged
e
graph
6
H25 = a12×(H-ratio – n1) + h1
Here, the maximum error between the linear approximation and actual characteristics is defined as “e”.
If “e” is larger than the maximum error for measuring humidity, it is necessary to make a finer portion and redo the
approximation procedure.
When all the program ROM areas are exhausted because there are too many approximate formulas, reduce the number
of approximate formulas by sacrificing accuracy.
The approximate formulas can be input as the ROM table data.
items:
The ROM table data are composed of the following 3
H-ratio
Slope a(5,25,45 degrees)
Offset h(5,25,45 degrees)
After finding the humidity using 25 degree’s table, decide applied expression h1 or hh from H-TEMP characteristics.
And calculate the humidity using applied expression.
Determine data length (= number of places) for the desired operation accuracy.
7
2.1.
Function overview
The humidity calculation module calculates the humidity value from the converted result of RC-ADC
and measured temperature based on the frequency ratio(that is, humidity ratio) – humidity conversion
table of the humidity sensor for C10-M53R made by Shinyei Technology. If you change the humidity
sensor, change this conversion table corresponded with the using humidity sensor.
Table2-1 Humidity calculation module API
Function name
Function
humid_calc
Calculate the humidity from the counter value of RC-ADC and temperature.
2.2.
Operating conditions
This section describes operating conditions, valid range, restrictions of this module.
-Valid temperature measurement range
-Humidity measurement range
：0~50 degrees centigrade (display character ‘–‘ of humidity means
that temperature is not within 0~50 degrees centigrade )
:20~95%
For the reference resistor Rs, 150K ohm is selected. Its resistance value is the same as the resistance value of the
humidity sensor at the condition of temperature 25 degrees centigrade and humidity 45%.
The following table shows the Humidity ratio - Humidity conversion table.
Table.2-1-2 Humidity ratio - Humidity Conversion Table
If you use this table in the program, use the shade field as data.
Table
address
0
1
2
3
4
5
6
7
8
9
10
11
12
13
Humidity
at 25 °C
105-95
95-80
80-75
74-70
69-60
59-55
54-45
44-40
39-35
34-30
29-25
24-20
19-18
17-16
Humidity
ratio
72796
26482
17757
11815
4954
3059
1024
568
310
160
81
39
17
6
25
°C
Slope
25 °C
264
340
601
882
1528
2767
5151
11520
20275
34882
66961
123894
123894
123894
Offset
25 °C
99614720
83886080
78643200
73400320
62914560
57671680
47185920
41943040
36700160
31457280
26214400
20971520
18299932
16884929
45
°C
8
Slope
45 °C
202
328
676
945
1469
2795
5227
11444
19269
35107
51425
123894
123894
123894
Offset
45 °C
91328599
76138872
70240883
64628578
54547315
49250937
38609802
33401393
28418816
23142116
19115612
13872732
11201144
9786141
5
°C
Slope
5 °C
360
398
577
922
1473
2646
5508
13322
21282
36767
63104
103632
188605
459052
Offset
5 °C
111995687
93548004
88510816
83034525
72927554
67913477
56699923
50637041
45133928
39607742
34666863
30281395
26214400
20971520
2.3.
Sample program
The below flowchart explains the procedure of humidity measurement using the humidity calculation module.
Main routine
Get the oscillaton counter value of
reference resistor RS1-CS1(Refer
‘AD conversion procedure’)
Get the oscillaton counter value of
sensor
RT1-CS1(Refer
‘AD
conversion procedure’)
Calculate Humidity
(Humid-calc function)
Fig2-4 Procedure of getting humidity
[Main routine]
z Change the circuit for the humidity sensor when the temperature measured.
z If the temperature is not within valid measurement range(50.1 degrees centigrade and up or under 0 degrees
centigrade), skip the measurement procedure, and display ‘- -%’.
1)Get the value of oscillation count for reference resistor RS1-CS1
Get the value of oscillation count for reference resistor RS1-CS1
(value of Counter B)
1 Mode of RC oscillation circuit: RS-CS oscillation mode
2 Base clock of counter A(BSCLK):LSCLK
3 Setting value of counter A: the base value of oscillation count for reference resistor RS-CS
(at interval of 500mS)
4 Setting value of counter B: 0
2)Get the value of oscillation count for sensor RT1-CS1
Get the value of oscillation count for sensor RT1-CS1
(value of Counter B)
1 Mode of RC oscillation circuit: RT-CS oscillation mode
2 Base clock of counter A(BSCLK):LSCLK
3 Setting value of counter A: the base value of oscillation count for reference resistor RS-CS
(at interval of 500mS)
4 Setting value of counter B: 0
3)Humidity calculation
Calculate the value of temperature by humid_calc function using the above mentioned oscillation count.
*For detailed procedure, refer “ML610Q400 Series Sample Program AP Notes For Sensor/Mesurement
Application” Section 3.2.3.1 A/D Conversion Procedure
9
［humid_calc］
1) Get a ratio for base value.
2) Calculate the ratio (H_ratio) from the below expression.
H_ratio = (the oscillation count base value of sensor RH-CS / the oscillation count value of sensor
RH-CS) × 1024
1024 means the revision for processing the integer calculation. Note that the circuit parameter Rh, Rs and
Cs must be selected in advance so that the value of H_ratio can not overflow its range when 1024 is
multiplied.
Next, search entries of humidity ratio from address 0 in the Humidity ratio–Humidity conversion table
until H_ratio is less than an entry of humidity ratio.
3) Calculate the distance between the searched humidity ratio and H_ratio by the following expression.
RH_distance = H_ratio - (the searched humidity ratio)
4) Calculate the humidity at 25 degrees centigrade (RH25) by using the slope and offset at 25 degrees
centigrade (Slope25 and Offset25), which correspond to the searched humidity ratio.
RH25 = (RH_distance × Slope25 + Offset25) >> 20
The value 20 is a multiplier that has already been multiplied to the slope and offset in the Humidity
ratio–Humidity conversion table in order to improve calculation accuracy.
5) Calculate the revised humidity RH from current temperature (T).
(a)If current temperature is 25 degrees centigrade and over, calculate the humidity at 45 degrees
centigrade (RH45) from the entries of 45 degrees centigrade in the Humidity ratio–Humidity conversion
table.
RH45 = (RH_distance × Slope45 + Offset45) >> 20
Calculate the humidity per temperature 1 degree between 25 and 45 degrees centigrade, and multiple it
by the difference between current temperature and 25 degrees centigrade, then it is possible to get current
humidity. The expression of this operation is as follows:
RH = RH25 - ((RH25 - RH45) / 20) × (T - 25)
(b)If current temperature is less than 25 degrees centigrade, calculate the humidity at 5 degrees
centigrade (RH5) from the entries of 5 degrees centigrade in the Humidity ratio–Humidity conversion
table.
RH5 = (RH_distance × Slope5 + Offset5) >> 20
Calculate the humidity per temperature 1 degree between 5 and 25 degrees centigrade, and multiple it by
the difference between current temperature and 25 degrees centigrade, then it is possible to get current
humidity. The expression of this operation is as follows:
RH = RH25 + ((RH5 - RH25) / 20) × (25 - T)
*After calculation, if the humidity is 100% and over, the result becomes 100%.
And if the humidity is 20% and under, the result becomes 20%.
Example:
In the case that the temperature is 40 degrees centigrade, a humidity ratio is 4000, it is possible to calculate the
humidity by the below procedure. In this case, use table address 5.
calculate the humidity at 25 degrees centigrade (RH25)
using RH25 = （RH_distance × Slope25 + Offset25） >> 20
RH25 = ((4000 - 3059) × 2767 + 57671680) >> 20 = 57
The temperature is over 25 degrees centigrade. Therefore calculate the humidity at 40 degrees
using the 45 degrees centigrade table
RH45 = ((4000 - 3059) × 2795 + 49250937) >> 20 = 49
Calculate an objective humidity (RH) from RH25 and RH45.
RH＝RH25 - （（RH25 - RH45） / 20）× （T - 25）
=57 - （57 - 49） / 20× (40 - 25)
=57 - 6
=51(%)
10
2.4.
Flowchart of humidity calculation
humid_calc
*hum=0
Search humidity ratio in the table from
the first entry.
temp<0 or temp>50
RH_distance = RH_ratio – (the
searched humidity ratio)
YES!
ret = -1
exit
NO!
Calculate the humidity of 25 degrees.
RH25=(Slope25*RH_distance + Offset25)>>
(coefficient for table revision)) << 16
*Multiply 0x10000 (shifts 16 bits) to improve the
precision of calculation.
base_ct=0 or
Humid_ct=0?
YES!
temp>=25?
NO!
ret = -1
YES!
exit
NO!
RH_ratio=(humid_ct <<11)/base_ct,
*Multiply 0x400 to improve the
precision of calculation.
RH_ratio>131281?
Calculate the humidity of 45 degrees.
RH45=((Slope45 * RH_distance + Offset45)>>
(coefficient for table revision)) << 16
Calculate the humidity of 5 degrees.
RH5=((Slope5 * RH_distance + Offset5)>>
(coefficient for table revision)) << 16
*Multiply 0x10000 (shifts 16 bits) to improve
the precision of calculation.
*Multiply 0x10000 (shifts 16 bits) to improve
the precision of calculation.
*hum=(RH25-((RH25-RH45)/20 * (T-25))
>> 16
*hum=(RH25+((RH5-RH25)/20 * (25-T))
>> 16
NO!
ret = -1
*hum>=100?
exit
YES!
NO!
*hum<=20?
YES!
*hum=100
*hum=20
NO!
ret = 0
exit
11
2.5.
Typical Peripheral Circuit Diagram
LCD
Coin Cell
NMI
VDD
COM0~3 (*)
SEG0~63 (*)
NMI
S1
S2
P00/CAP0
EXVDDV
P01/CAP1
EXGND
P02
S3
P03
S4
RESET_N
ML610Q4xx
P30/IN0
P31/CS0
CX
Cd
Cc
Cb
Ca
VDDX
P32/RS0
VL4
P33/RT0
VL3
P34/RCT0
VL2
P35/RCM
VL1
P44/IN1
C4
P45/CS1
C34
P46/RS1
C3
C2
1/4 Bias
P47/RT1
CS0
CVR0
RS0
RT0
CS1
CVR1
RS1
RT1
C12
C1
XT0
CGL
AVDD
AVref
XL
CDL
AVSS
XT1
32.768KHz
Xtal
P22
/MD0
P43 P41 P40
P42 P43
/RXD /TXD
AIN0
(Output) /SCL /SDA
Buzzer
ICL2332
GND R1In T1Out
4
3
V+
2
GND TXD RXD
V-
WP SCL SDA
9-pin D-SUB
A0 A1
CV
:1uF
:1uF
CL0
:0.1uF
CL1
:1uF
C1
CX
:0.1uF
Ca,Cb,Cc,Cd
:1uF
:1uF
C12,C34
: No ( 0 pF )
CGL
: No ( 0 pF )
CDL
Vcc
2
I C EEPROM
A2
Vss
RS0
CS0
CVR0
RT0
: 10 Kohm
: 560 pF
: 820 pF
: 103AT (Semitec) thermister
RS1
CS1
CVR1
RT1
: 150 Kohm
: 680 pF
: 820 pF
: C10-M53R (Shinyei) humidity sensor
Fig2-5 Peripheral Circuit Diagram
(*) The number of COM/SEG pin that can be connected to LCD panel depends on the type of the LCD driver built into
the MCU. Please see the chapter “LCD Driver” of the User’s Manual for your target MCU.
For more detail about the peripheral curcuit, please see the “ML610Q400 Series Demo Kit Hardware User’s Manual”.
12
2.6.
How to prepare the Humidity ratio - Humidity conversion table
2.6.1.
Selection of the reference resistor
This humidity calculation module calculates the humidity value by using the frequency count value from RC-ADC
oscillation of the humidity sensor and the reference resistor. Therfore it is necessary to estimate the frequency count
value of the humidity sensor, in advance.
If the frequency count value of the humidity sensor and the reference resistor is the same, we can regard that the
humidity sensor and the reference resistor have the same impedance. It means that the frequency count value of the
humidity sensor can be estimated as the ratio against the count value of the reference resister, from the
humidity-resistance characteristics of the humidity sensor.
Example:
In the following case,
the reference resistor = 150 Kohm
the frequency count value of the humidity sensor = 2040
the frequency count value of the reference resistor = 1024
the ratio of frequency count (the humidity sensor / the reference resistor) is about 2. The impedance of the humidity
sensor can be estimated to be about 300 Kohm.
* About the way of calculating the frequency count value from the resistance (impedance), refer to the chapter “RC
Oscillation Type A/D Converter (RC-ADC)” of the User’s Manual for your target MCU.
For the sample program, the resister of 150 Kohm is selected as the reference resistor so that the ratio of frequency
count is 1 on the condition that temparature is 25 degrees centigrade and humidity is 45%rh.
2.6.2.
Conversion from the Humidity-Resictance chracteristic to the Humidity-Count ratio charateristic
To estimate the RC-ADC frequency count value and calculate the humidity at each temparature (25, 45 and 5 degrees
centigrade), follow the procedure below.
1.
2.
3.
4.
Calculate the RC-ADC frequency count value of the reference resistor (150 Kohm), from the Humidity-Resistance
characteristic at 25 degrees centigrade.
Similarly, calculates the RC-ADC frequency count value of other impedances. Then, calculate the ratio (A) against
the count value that was calculated in the above procedure 1, and make the approximation formula (f25).
Extract the impedance of the humidity sensor from the Humidity-Resistance characteristic at 45 degrees centigrade.
Then, calculates the RC-ADC frequency count value and the ratio against the count value of the reference resistor
for each impedance of the humidity sensor.
Make the the approximate formula (f45) of the Humidity-Count ratio characteristic, from the result of the above
procedure 3.
Example:
%rh
40
45
50
55
60
Count ratio
against the
Impedance reference
at 45°C
resistor
250
100
500
60
1000
37
2000
24
4000
15
13
Humidity
Humidity-Count ratio characteristic (45°C)
60
55
50
f45＝a60×(Count ratio – n4)＋f45(n4)
45
f45＝a55×(Count ratio – n3)＋f45(n3)
40
f45＝a50×(Count ratio – n2)＋f45(n2)
n1 n2
n3
n4
f45＝a45×(Count ratio – n1)＋f45(n1)
n5
Count ratio
5.
Similarly, extract the impedance of the humidity sensor from the Humidity-Resistance characteristic at 5 degrees
centigrade. Then, calculates the RC-ADC frequency count value and the ratio against the count value of the
reference resistor for each impedance of the humidity sensor. From this result, make the the approximate formula
(f5) of the Humidity-Count ratio characteristic.
Note: If the RC-ADC frequency count value is not enough to calcurate the count ratio, it is necessary to consider
adjusting the reference registor and the capacitor (Cs).
2.6.3.
Making up into a table for humidity calculation
By the following procedure, calculate the slope and offset of the approximate formula of the Humidity-Count ratio
characteristic for 25, 45and 5 degrees centigrade, and make up them into a table. The resistance at the condition that
temparature is 25 degrees centigrade and humidity is 45%rh is selected as the reference register, and the count ratio
against this reference registor is searched in the table. Therefore it is necessary to calculate the humidity for 45 and 5
degrees centigrade, that corresponds to each entry of the count ratio in the Humidity-Count ratio characteristic for 25
degrees centigrade.
1. From the approximate formula (f45), calculate the humidity f45(n25), which corresponds to each entry of the
count ratio in the Humidity-Count ratio characteristic for 25 degrees centigrade.
Exampe:
%rh
40
45
50
55
60
Entry of count ratio
in 25°C
characteristic
n25
320
750
1200
2050
4010
Range of count ratio in
45℃ characteristic
250<= x < 500
500 <= x < 1000
1000 <= x < 2000
2000 <= x < 4000
Slope
Offset
a4540
a4545
a4550
a4555
b4540
b4545
b4550
b4555
14
When the count ratio is 320, the humidity at 45 °C is : f45(320) = a4540 * (320-250) + b4540
When the count ratio is 2050, the humidity at 45 °C is : f45(2050) = a4555 * (2050-2000) + b4555
By the above procedure, the humidity at 45 degrees centigrade, which corresponds to each entry of the count
ratio in the Humidity-Count ratio characteristic for 25 degrees centigrade, is caluculated as follows.
Humidity
2.
Humidity–Count ratio characteristic (45°C)
60
55
50
45
40
250 500 1000
320 750 1200
2000
2050
4000
Count ratio
Entries of count ratio in 25°C characteristic
3.
Similarly, calculates the humidity at 5 degrees centigrade, which corresponds to each entry of the count ratio in
the Humidity-Count ratio characteristic for 25 degrees centigrade.
4. Make up the following data into a table.
The count ratio at 25 degrees centigrade, that was calculated at the procedure 2 in the chapter 2.6.2.(A)
The slope in the Humidity-Count ratio characteristic at 25 degrees centigrade.
The offset in the Humidity-Count ratio characteristic at 25 degrees centigrade.
The slope in the Humidity-Count ratio characteristic at 45 degrees centigrade.
The offset in the Humidity-Count ratio characteristic at 45 degrees centigrade.
The slope in the Humidity-Count ratio characteristic at 5 degrees centigrade.
The offset in the Humidity-Count ratio characteristic at 5 degrees centigrade.
15
3. Celsius Fahrenheit conversion module
3.1. function overview
This module converts from Fahrenheit to Celsius.
Table3.1 API list
Function name
convertCtoF_asm
function
Convert from Celsius degrees centigrade to Fahrenheit degrees
centigrade.
3.2. Operation condition
This section describes operating conditions, valid range, restrictions of this module.
Calculation range
:105.0~-50.0 degrees centigrade
[Note]
U8 has a powerful ’Decimal adjustment instruction’. And this instruction is so useful for this module.
However, CCU8 compiler does not support this instruction. So, this module is made by assembler
language.
By using’ Decimal adjustment instruction’ and shift operation, it is possible to process this conversion
effectively
See the below description for more detail.
Operation overview
Transform the expression to process faster like the below:
1F=9/5C+32=1.8C+32
// Decompose 1.8C to C+8/10C
21.8C=C+8C/10=C+((C+C)×2)×2/10
// 8 can transform to 2x2x2. Then it is possible to use shift
operation instead of multiple operation.
3if C>=0 then
F= (C+((C+C)×2)×2/10)+32
else
F=32-(C+((C+C)×2)×2/10)
end
16
Revision History
17
Revision History
Edition
Page
Isuue Date
Contents
Before
After
1
June 26, 2009
–
–
First Edition
2
January 27, 2010
5
2
Description about the resistance mesurement method,
which is used by the temperature calculation module, is
corrected.
18