AN1950 Water Level Monitoring

Freescale Semiconductor
Application Note
AN1950
Rev 4, 11/2006
Water Level Monitoring
by: Michelle Clifford, Applications Engineer
Sensor Products, Tempe, AZ
INTRODUCTION
Many washing machines currently in production use a
mechanical sensor for water level detection. Mechanical
sensors work with discrete trip points enabling water level
detection only at those points. The purpose for this reference
design is to allow the user to evaluate a pressure sensor for
not only water level sensing to replace a mechanical switch,
but also for water flow measurement, leak detection, and other
solutions for smart appliances. This system continuously
monitors water level and water flow using the temperature
compensated MPXM2010GS pressure sensor in the low cost
MPAK package, a dual op-amp, and the MC68HC908QT4,
eight-pin microcontroller.
SYSTEM DESIGN
Pressure Sensor
The pressure sensor family has three levels of integration
— Uncompensated, Compensated and
Integrated. For this design, the MPXM2010GS compensated
pressure sensor was selected because it has both
temperature compensation and calibration circuitry on the
silicon, allowing a simpler, yet more robust, system circuit
design. An integrated pressure sensor, such as the
MPXV5004G, is also a good choice for the design eliminating
the need for the amplification circuitry.
measuring is between 0–40 cm. This corresponds to a
pressure range of 0–4 kPa. Therefore, the MPXM2010GS
was selected for this system. The sensor sensitivity is
2.5 mV/kPa, with a full-scale span of 25 mV at the supply
voltage of 10 VDC. The full-scale output of the sensor changes
linearly with supply voltage, so a supply voltage of 5 V will
return a full-scale span of 12.5 mV.
(VS actual / VS spec) * VOUT full-scale spec = VOUT full-scale
(5.0 V/ 10 V) x 25 mV = 12.5 mV
Since this application will only be utilizing 40 percent of the
pressure range, 0–4kPa, our maximum output voltage will be
40 percent of the full-scale span.
VOUT FS * (Percent FS Range) = VOUT max
12.5 mV * 40% = 5.0 mV
The package of the pressure sensor is a ported MPAK
package. This allows a tube to be connected to the sensor and
the tube is connected to the bottom of the tub. This isolates the
sensor from direct contact with the water. The small size and
low cost are additional features making this package a perfect
fit for this application.
Figure 2. A Ported Pressure Sensor
Figure 1. Water Level Reference Design Featuring a
Pressure Sensor
The height of most washing machine tubs is 40 cm,
therefore the water height range that this system will be
© Freescale Semiconductor, Inc., 2006. All rights reserved.
Table 1. MPXM2010D OPERATING CHARACTERISTICS (VS = 10 VDC, TA = 25°C unless otherwise noted, P1 > P2)
Characteristic
Symbol
Min
Typ
Max
Unit
Pressure Range
POP
0
—
10
kPa
Supply Voltage
VS
—
10
16
Vdc
Supply Current
IO
—
6.0
–
mAdc
Full Scale Span
VFSS
24
25
26
mV
Voff
-1.0
—
1.0
mV
DV/DP
—
2.5
—
mV/kPa
—
-1.0
—
1.0
%VFSS
Offset
Sensitivity
Linearity
Amplifier Induced Errors
The sensor output needs to be amplified before being
inputted directly to the microcontroller through an eight-bit A/D
input pin. To determine the amplification requirements, the
pressure sensor output characteristics and the 0-5 V input
range for the A/D converter had to be considered.
The amplification circuit uses three op-amps to add an
offset and convert the differential output of the MPXM2010GS
sensor to a ground-referenced, single-ended voltage in the
range of 0–5.0 V.
The pressure sensor has a possible offset of ±1 mV at the
minimum rated pressure. To avoid a nonlinear response when
a pressure sensor chosen for the system has a negative offset
(VOFF), we added a 5.0 mV offset to the positive sensor output
signal. This offset will remain the same regardless of the
sensor output. Any additional offset the sensor or op-amp
introduces is compensated for by software routines invoked
when the initial system calibration is done.
To determine the gain required for the system, the
maximum output voltage from the sensor for this application
had to be determined. The maximum output voltage from the
sensor is approximately 12.5 mV with a 5.0 V supply since the
full-scale output of the sensor changes linearly with supply
voltage. This system will have a maximum pressure of 4 kPa
at 40 cm of water. At a 5.0 V supply, we will have a maximum
sensor output of 5 mV at 4 kPa of pressure. To amplify the
maximum sensor output to 5.0 V, the following gain is needed:
Gain = (Max Output needed) / (Max Sensor Output
and Initial Offset) = 5.0 V / (0.005 V + 0.005) = 500
The gain for the system was set for 500 to avoid railing from
possible offsets from the pressure sensor or the op-amp.
The Voltage Outputs from the sensor are each connected
to a non-inverting input of an op-amp. Each op-amp circuit has
the same resistor ratio. The amplified voltage signal from the
negative sensor lead is VA. The resulting voltage is calculated
as follows:
VA = (1+R8/R6) * V4
= (1+10/1000) * V4
The amplified voltage signal from the positive sensor lead
is VB. This amplification adds a small gain to ensure that the
positive lead, V2, is always greater than the voltage output
from the negative sensor lead, V4. This ensures the linearity
of the differential voltage signal.
VB = (1+R7/R5) * V2 – (R7/R5) * VCC
= (1+10/1000) * V2 + (10/1000)*(5.0 V)
= (1.001) * V2 + 0.005 V
The difference between the positive sensor voltage, VB,
and the negative sensor voltage, VA is calculated and
amplified with a resulting gain of 500.
VC = (R12/R11) * (VB – VA)
= (500 K/1K) * (VB – VA)
= 500 * (VB – VA)
The output voltage, VC, is connected to a voltage follower.
Therefore, the resulting voltage, VC, is passed to an A/D pin of
the microcontroller.
The range of the A/D converter is 0 to 255 counts. However,
the A/D Values that the system can achieve are dependent on
the maximum and minimum system output values:
Count = (VOUT – VRL) / ( VRH – VRL) x 255
where VXdcr = Transducer Output Voltage
VRH = Maximum A/D voltage
VLH = Minimum A/D voltage
Count (0 mm H20) = (2.5 – 0) / (5.0 – 0) * 255 = 127
Count (40 mm H20) = (5.0 – 0) / (5.0 – 0) * 255 = 255
Total # counts = 255 – 127 = 127 counts.
The resolution of the system is determined by the mm of
water represented by each A/D count. As calculated above,
the system has a span of 226 counts to represent water level
up to and including 40 cm. Therefore, the resolution is:
Resolution = mm of water / Total # counts
= 400mm/127 counts = 3.1 mm per A/D count
= (1.001) * V4
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Freescale Semiconductor
R6
10K
V4sensor
R8
10Ω
6
5
-
7
VA
R12
500K
+
VCC
R11
1K
13
R7
10Ω
VCC
12
R9
1K
R5
10K
V2sensor
2
3
-
1
+
C5
0.1µF
VC
14
4
-
9
10
8
VOUT
+
11
R10
500K
VB
+
Figure 3. Amplification Scheme
Microprocessor
To provide the signal processing for pressure values, a
microprocessor is needed. The MCU chosen for this
application is the MC68HC908QT4. This MCU is perfect for
appliance applications due to its low cost, small eight-pin
package, and other on-chip resources. The MC68HC908QT4
provides: a four-channel, eight-bit A/D, a 16-bit timer, a
trimmable internal timer, and in-system FLASH programming.
The central processing unit is based on the high
performance M68HC08 CPU core and it can address 64
Kbytes of memory space. The MC68HC908QT4 provides
4096 bytes of user FLASH and 128 bytes of random access
memory (RAM) for ease of software development and
maintenance. There are five bi-directional input/output lines
and one input line shared with other pin features.
The MCU is available in eight-pin as well as 16-pin
packages in both PDIP and SOIC. For this application, the
eight-pin PDIP was selected. The eight-pin PDIP was chosen
for a small package, eventually to be designed into
applications as the eight-pin SOIC. The PDIP enables the
customer to reprogram the software on a programming board
and retest.
Display
Depending on the quality of the display required, water
level and water flow can be shown with two LEDs. If a higher
quality, digital output is needed, an optional LCD interface is
provided on the reference board. Using a shift register to hold
display data, the LCD is driven with only three lines outputted
from the microcontroller: an enable line, a data line, and a
clock signal. The two LEDs are multiplexed with the data line
and clock signal
PTA3
PTA4
PTA5
HC908QT4
R2
1K
A
B
CLK
HC164
R3
1K
EN
RS
RW
LCD
DB0
DB1
DB2
DB3
DB4
DB5
DB6
DB7
Figure 4. Multiplexed LCD Circuit
Multiplexing of the microcontroller output pins allows
communication of the LCD to be accomplished with three pins
instead of eight or 11 pins of I/O lines usually needed. With an
eight-bit shift register, we are able to manually clock in eight
bits of data. The enable line (EN) is manually accepted when
eight bytes have been shifted in, telling the LCD the data on
the data bus is available to execute.
The LEDs are used to show pressure output data by
displaying binary values corresponding to a pressure range.
Leak detection, or water-flow speed, is displayed by blinking a
green LED at a speed relating to the speed of water flow. The
red LED displays the direction of water flow. Turning the red
LED off signifies water flowing into the tub. Turning the red
LED on signifies water flowing out of the tub, or alternatively,
there is a leak.
Digital values for water height, rate of water flow, and
calibration values are displayed if an LCD is connected to the
board
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OTHER
This system is designed to run on a 9.0 V battery. It
contains a 5.0 V regulator to provide 5.0 V to the pressure
sensor, microcontroller, and LCD. The battery is mounted on
the back of the board using a space saving spring battery clip.
Table 2. Parts List
Ref.
Qty
Description
Value
Vendor
Part No.
U2
1
Pressure Sensor
1
Freescale
MPXM2010GS
C1
1
Vcc Cap
0.1µf
Generic
—
C2
1
Op-Amp Cap
0.1µf
Generic
—
C3
1
Shift Register Cap
0.1µf
Generic
—
D1
1
Red LED
—
Generic
—
D2
1
Green LED
—
Generic
—
S2, S3
2
Pushbuttons
—
Generic
—
U1
1
Quad Op-Amp
—
ADI
AD8544
U3
1
Voltage Regulator
5.0 V
Fairchild
LM78L05ACH
U4
1
Microcontroller
8-pin
Freescale
MC68HC908QT4
R1
1
¼ W Resistor
22 K
Generic
—
R2
1
¼ W Resistor
2.4 K
Generic
—
R3, R6
2
¼ W Resistor
1.2 M
Generic
—
R4, R5
2
¼ W Resistor
1.5 K
Generic
—
R7, R8
2
¼ W Resistor
10 K
Generic
—
R9, R10
2
¼ W Resistor
1.0 K
Generic
—
U6
1
LCD (Optional)
16 x 2
Seiko
L168200J000
U5
1
Shift Registor
—
Texas Instruments
74HC164
Smart Washer Software
This application note describes the first software version
available. However, updated software versions may be
available with further functionality and menu selections.
Software User Instructions
When the system is turned on or reset, the microcontroller
will flash the selected LED and display the program title on the
LCD for five seconds, or until the select (SEL) button is
pushed. Then the menu screen is displayed. Using the select
(SEL) pushbutton, it is easy to scroll through the menu options
for a software program. To run the water level program, use
the select button to highlight the Water Level option, then
press the enter (ENT) pushbutton. The Water Level program
will display current water level, the rate of flow, a message if
the container is Filling, Emptying, Full, or Empty, and a
scrolling graphical history displaying data points representing
the past forty level readings.
The Water Level is displayed by retrieving the digital
voltage from the internal A/D Converter. This voltage is
converted to pressure in millimeters of water and then
displayed on the LCD.
buttons on system power-up enters the calibration mode. At
this point, the calibration menu is displayed with the previously
sampled offset voltage. To recalibrate the system, expose the
sensor to atmospheric pressure and press the SEL button
(PB1). At this point, the zero offset voltage will be sampled and
saved to a location in the microcontroller memory. To obtain
the second calibration point, place the end of the plastic tube
from the pressure sensor to the bottom of a container holding
40 mm of water. Then press the ENT button (PB2). The
voltage output will be sampled, averaged and saved to a
location in memory. To exit the calibration mode, press the
SEL (PB1) button.
Calibration and Calibration Software
To calibrate the system, a two-point calibration is
performed. The sensor will take a calibration point at 0 mm
and at 40 mm of water. Depressing both the SEL and ENT
Figure 5. Water Level System Set-Up
for Demonstration
AN1950
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Freescale Semiconductor
Converting Pressure to Water Level
Hydrostatic pressure being measured is the pressure at the
bottom of a column of fluid caused by the weight of the fluid
and the pressure of the air above the fluid. Therefore, the
hydrostatic pressure depends on the air pressure, the fluid
density and the height of the column of fluid.
P= Pa + ρ g ∆h
where P = pressure
Pa = pressure
ρ = mass density of fluid
g = 9.8066 m/s^2
h = height of fluid column
To calculate the water height, we can use the measured
pressure with the following equation, assuming the
atmospheric pressure is already compensated for by the
selection of the pressure sensor being gauge:
∆h = P \ ρ g
The function first clears the 40 pressure readings it updates
for the Graphical History. The history then enters the loop first
displaying eight special characters, each containing five data
points of water level history. The function adcbyta is called to
obtain the current averaged A/D value. The function LfNx is
called to convert the A/D value to a water level. It is then
compared to the calibration points, the maximum and
minimum points, to determine if the container is full or empty.
If true, then it displays the corresponding message. The
current water level is compared to the previous read and
displays the message filling if it has increased, emptying if it
has decreased, and steady if it has not changed.
The water level calculation has to be converted to decimal
in order to display it in the LCD. To convert the water level
calculation to decimal, the value is continually divided with the
remainder displayed to the screen for each decimal place. To
display the Rate of Water Flow, the sign of the value is first
determined. If the value is negative, the one's complement is
taken, a negative sign is displayed, and then the value is
continually divided to display each decimal place. If the
number is positive, a plus sign.
Software Function Descriptions
Level Function
Main Function
The Level function initializes the graphics characters. Once
this is complete, it continues looping to obtain an
average A/D reading, displaying the Water Level, the Water
Flow, and a Graphical History until simultaneously depressing
both PB1 and PB2 to return to the main function.
The function first clears the 40 pressure readings it updates
for the Graphical History. The history then enters the loop first
displaying eight special characters, each containing five data
points of water level history. The function adcbyta is called to
obtain the current averaged A/D value. The function LfNx is
called to convert the A/D value to a water level. It is then
compared to the calibration points, the maximum and
minimum points, to determine if the container is full or empty.
If true, then it displays the corresponding message. The
current water level is compared to the previous read and
displays the message filling if it has increased, emptying if it
has decreased, and steady if it has not changed.
The water level calculation has to be converted to decimal
in order to display it in the LCD. To convert the water level
calculation to decimal, the value is continually divided with the
remainder displayed to the screen for each decimal place. To
display the Rate of Water Flow, the sign of the value is first
determined. If the value is negative, the one's complement is
taken, a negative sign is displayed, and then the value is
continually divided to display each decimal place. If the
number is positive, a plus sign is displayed to maintain the
display alignment and the value is continually divided to
display each decimal place.
The most complicated part of this function is updating the
graphics history display. The characters for the 16x2 LCD
chosen for this reference design are 8x5 pixels by default.
Therefore, each special character that is created will be able
to display five water level readings. Since the height of the
special character is eight pixels, each vertical pixel position
will represent a water level in increments of 20 mm.
The main function calls an initialization function Allinit calls
a warm-up function, Warmup, to allow extra time for the LCD
to initialize, then checks if buttons PB1 and PB2 are
depressed. If they are depressed concurrently, it calls a
calibration function Calib. If they are not both pressed, it
enters the main function loop. The main loop displays the
menu, moves the cursor when the PB1 is pressed and
enters the function corresponding to the highlighted menu
option when PB2 is depressed.
Calibration Function
The calibration function is used to obtain two calibration
points. The first calibration point is taken when the head tube
is not placed in water to obtain the pressure for 0 mm of water.
The second calibration point is obtained when the head tube
is placed at the bottom of a container with a height of 160 mm.
When the calibration function starts, a message appears
displaying the A/D values for the corresponding calibration
points currently stored in the flash. To program new calibration
points, press PB1 to take 256 A/D readings at 0 mm of water.
The average is calculated and stored in a page of flash. Then
the user has the option to press PB1 to exit the calibration
function or obtain the second calibration point. To obtain the
second calibration point, the head tube should be placed in
160 mm of water, before depressing PB2 to take 256 A/D
readings. The average is taken and stored in a page of flash.
Once the two readings are taken, averaged, and stored in the
flash, a message displays the two A/D values stored.
Level Function
The Level function initializes the graphics characters. Once
this is complete, it continues looping to obtain an average A/D
reading, displaying the Water Level, the Water Flow, and a
Graphical History until simultaneously depressing both PB1
and PB2 to return to the main function.
Resolution = (H1 – H0) / D
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5
where H1 and H2 are the maximum and minimum water levels
respectively and D is the possible datapoints available per
character.
Resolution = (160mm– 0mm) / 8.0 = 20 mm / data point.
The graphical history is displayed using the eight special
characters. To update the graphics, all the characters have to
be updated. The characters are updated by first positioning a
pixel for the most recent water level reading in the first column
of the first character. Then the four right columns of the first
character are shifted to the right. The pixel in the last column
of that character is carried to the first column of the next
character. This column shifting is continued until all 40 data
points have been updated in the eight special characters.
LfNx Function
The LfNx function calculates the water level from the
current A/D pressure reading. The A/D Pressure value is
stored in Register A before this function is called. Using the
A/D value and the calibration values stored in the flash, the
water level is calculated from the following function:
RBRA: = (NX –N1) * 160 / (N2 – N1),
where NX is the current A/D Value
N1 is the A/D Value at 0 mm H20
N2 is the A/D Value at 160 mm H20
To simplify the calculation, the multiplication is done first.
Then the function NdivD is called to divide the values.
NdivD Function
The NdivD function performs a division by counting
successive subtractions of the denominator from the
numerator to determine the quotient. The denominator is
subtracted from the numerator until the result is zero. If there
is an overflow, the remainder from the last subtraction is the
remainder of the division.
wrflash and ersflsh Functions
The wrflash and ersflsh functions are used to write to and
erase values from the flash. For more information regarding
flash functionality, refer to Section Four, Flash Memory from
the MC68HC908QY4/D Databook.
ALLINIT Function
The Allinit function disables the COP for this version of
software, sets the data direction bits, and disables the data to
the LCD and turns off the LCD enable line. It also sets up the
microcontroller's internal clock to half the speed of the bus
clock. See Section 15, Computer Operating Properly, of the
MC68908QT4 datasheet for information on utilizing the COP
module to help software recover from runaway code.
bintasc Function
The binasc function converts a binary value to its ascii
representation.
A/D Functions
The A/D functions are used to input the amplified voltage
from the pressure sensor from channel 0 of the A/D converter.
The function adcbyti will set the A/D control register, wait for
the A/D reading and load the data from the A/D data register
into the accumulator. The function adcbyta is used to obtain an
averaged A/D reading by calling adcbyti 256 times and
returning the resulting average in the accumulator.
LCD Functions
The LCD hardware is set up for multiplexing three pins from
the microcontroller using an eight-bit shift register. Channels
three, four, and five are used on port A for the LCD enable (E),
the LCD reset (RS), and the shift register clock bit,
respectively. The clock bit is used to manually clock data from
channel four into the eight-bit shift register. This is the same
line as the LCD RS bit because the MSB of the data is low for
a command and high for data. The RS bit prepares the LCD
for instructions or data with the same bit convention. When the
eight bits of data are available on the output pins of the shift
register, the LCD enable (E) is toggled to receive the data.
The LCD functions consist of an initialization function lcdinit
which is used once when the system is started and five output
functions. The functions lcdcmdo and lcdchro both send a
byte of data. The function shiftA is called by both lcdcmdo and
lcdchro to manually shift eight bits of data into the shift register.
The function lcdnibo converts the data to binary before
displaying. The lcdnibo displays a byte of data by calling
lcdnibo for each nibble of data. The function lcdnibo enables
strings to be easily added to the software for display. The
function accepts a comma- delimited string of data consisting
of 1–2 commands for clearing the screen and positioning the
cursor. It then continues to output characters from the string
until the @ symbol is found, signally the end of the string.
CONCLUSION
The water level reference design uses a MPXM2010GS
pressure sensor in the low cost MPAK package, the low cost,
eight-pin microcontroller, and a quad op-amp to amplify the
sensor output voltage. This system uses very few
components, reducing the overall system cost. This allows for
a solution to compete with a mechanical switch for water level
detection but also offer additional applications such as
monitoring water flow for leak detection, and the other
applications for smart washing machines.
WARMUP Function
The Warmup function alternates the blinking of the two
LEDs ten times. This gives the LCD some time to warm up.
Then the function warmup calls the LCD initialization function,
lcdinit.
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SOFTWARE LISTING
;NitroWater 2.0 24Jan03
;-------------;
;Water Level Reference Design
;****************************
; - uses 908QT4 (MC68HC908QT4) and MPAK (MPXM2010GS)
; CALIB: 2-point pressure calibration (0mm and 160mm)
; LEVEL: displays water level, flow, and graphics
; UNITS: allows user to select between cm and inches
;
;__________________________________________________________
ram
equ $0080
;memory pointers
rom
equ $EE00
vectors equ $FFDE
;__________________________________________________________
porta equ $00
;registers
ddra
equ $04
config2 equ $1E
config1 equ $1F
tsc
equ $20
tmodh equ $23
icgcr equ $36
adscr equ $3C
adr
equ $3E
adiclk equ $3F
flcr
equ $FE08
flbpr equ $FFBE
;__________________________________________________________
org $FD00
;flash variables
N1
db $96
;1st calibration pt. = 0mm
org $FD40
N2
db $F6
;2nd calibration pt. = 160mm
org $FD80
;__________________________________________________________
org vectors
dw cold
;ADC
dw cold
;Keyboard
dw cold
;not used
dw cold
;not used
dw cold
;not used
dw cold
;not used
dw cold
;not used
dw cold
;not used
dw cold
;not used
dw cold
;not used
dw cold
;TIM Overflow
dw cold
;TIM Channel 1
dw cold
;TIM Channel 0
dw cold
;not used
dw cold
;IRQ
dw cold
;SWI
dw cold
;RESET ($FFFE)
;__________________________________________________________
org ram
BB
ds 1
;variables
flshadr ds 2
flshbyt ds 1
memSP ds 2
mem03 ds 2
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CNT
ds 1
Lgfx
ds 1
weath ds 1
UnitType ds 1
UnitDiv ds 1
UnitEmpt ds 1
UnitFull ds 1
ram0
ds 1
NC
ds 1
NB
ds 1
NA
ds 1
DC
ds 1
DB
ds 1
DA
ds 1
MB
ds 1
MA
ds 1
OB
ds 1
OA
ds 1
RB
ds 1
RA
ds 1
P0C
ds 1
P0B
ds 1
P0A
ds 1
NPTR
ds 1
ramfree ds 80
;used both for running RAM version of wrflash & storing 40 readings
;__________________________________________________________
;__________________________________________________________
;__________________________________________________________
org rom
cold: rsp
;reset SP if any issues (all interrupt vectors point here)
jsr ALLINIT
;general initialization
jsr WARMUP
;give LCD extra time to initialize
brset 1,porta,nocalib
brset 2,porta,nocalib
jmp CALIB
;only do calibration if SEL & ENT at reset
nocalib: ldhx #msg01
;otherwise skip and show welcome messages
jsr lcdstro
;"Reference Design" msg
jsr del1s
;wait 1s
ldhx #msg01a
;"Water Level" msg
jsr lcdstro
jsr del1s
;wait 1s
initCM: ldhx #$A014
sthx UnitType
ldhx #$039E
sthx UnitEmpt
MENU:
jsr
clr
lda
jsr
luke:
;initialize default units to cm ($A0=cm, $3F=in)
;UnitType set to $A0; UnitDiv set to $14
;UnitEmpt set to $03; UnitFull set to $9E
ldhx #msg01b
lcdstro
;Menu msg
RA
;menu choice=0 to begin with
#$0D
lcdcmdo
;blink cursor on menu choice
ldx RA
;get current menu choice
clrh
lda menupos,x
;and look up corresponding LCD address
jsr lcdcmdo
;reposition cursor
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warm:
brclr 1,porta,PB1 ;check for SEL
brclr 2,porta,PB2 ;or for ENT
bclr 4,porta
;otherwise
bset 5,porta
;turn on "SEL" LED
jsr del100ms
;delay
bset 4,porta
;toggle LEDs
bclr 5,porta
;"ENT" now on: means choice is SEL ***or*** ENT
jsr del100ms
;delay and repeat until SEL or ENT
bra warm
PB1:
inc RA
;***SEL*** toggles menu choices
lda RA
cmp #$02
;menu choices are $00 and $01
bne PB1ok
clr RA
;back to $00 when all others have been offered
PB1ok: bclr 4,porta
bclr 5,porta
;LEDs off
jsr del100ms
;wait a little bit
brclr 1,porta,PB1ok ;make sure they let go of SEL
bra luke
PB2:
bclr 4,porta
;***ENT*** confirms menu choice
bclr 5,porta
;LEDs off
lda RA
;get menu choice
bne skip00
jmp LEVEL
;do ===LEVEL=== if choice=$01
skip00: jmp UNITS
;do ===UNITS=== if choice=$00
;__________________________________________________________
;__________________________________________________________
CALIB: lda #$01
jsr lcdcmdo
clr ram0
ldhx #msg05
;===CALIB=== 2-point calibration
jsr lcdstro
;Calibration current values
lda N1
;0mm
jsr lcdbyto
lda #'/'
jsr lcdchro
lda N2
;160mm
jsr lcdbyto
bset 4,porta
bset 5,porta
;LEDs on
lego1: brclr 1,porta,lego1
lego2: brclr 2,porta,lego2
bclr 4,porta
bclr 5,porta
;LEDs off when both SEL & ENT are released
jsr del1s
jsr del1s
;wait 2s
ldhx #msg05a
jsr lcdstro
;show instructions
waitPB1: brset 2,porta,no2 ;if ENT is not pressed, skip
jmp nocalib
;if ENT is pressed then cancel calibration
no2:
brclr 1,porta,do1st ;if SEL is pressed then do 1st point cal
bra waitPB1
;otherwise wait for SEL or ENT
do1st: ldhx #msg05b
;1st point cal: show values
jsr lcdstro
clr CNT
;CNT will count 256 A/D readings
clr RB
clr RA
;RB:RA will contain 16-bit add-up of those 256 values
AN1950
Sensors
Freescale Semiconductor
9
do256: lda #$C9
jsr lcdcmdo
;position LCD cursor at the right spot
lda CNT
deca
jsr lcdbyto
;display current iteration $FF downto $00
lda #':'
jsr lcdchro
jsr adcbyti
;get reading
add RA
sta RA
lda RB
adc #$00
sta RB
;add into RB:RA (16 bit add)
jsr lcdbyto
;show RB
lda RA
jsr lcdbyto
;then RA
dbnz CNT,do256
;and do 256x
lsl RA
;get bit7 into carry
bcc nochg
;if C=0 then no need to round up
inc RB
;otherwise round up
nochg: lda RB
;we can discard RA: average value is in RB
ldhx #N1
;point to flash location
jsr wrflash
;burn it in!
ldhx #msg05c
;ask for 160mm
jsr lcdstro
waitPB2: brset 2,porta,waitPB2 ;wait for ENT
ldhx #msg05d
;2nd point cal: show values
jsr lcdstro
clr CNT
;ditto as 1st point cal
clr RB
clr RA
do256b: lda #$C9
jsr lcdcmdo
lda CNT
deca
jsr lcdbyto
lda #':'
jsr lcdchro
jsr adcbyti
add RA
sta RA
lda RB
adc #$00
sta RB
jsr lcdbyto
lda RA
jsr lcdbyto
dbnz CNT,do256b
lsl RA
bcc nochg2
inc RB
nochg2: lda RB
cmp N1
;compare N2 to N1
bne validcal
;if different, we are OK
ldhx #msg05e
;otherwise warn of INVALID CAL!
jsr lcdstro
jsr del1s
jsr del1s
jsr del1s
;wait 2s
jmp CALIB
;try cal again
AN1950
10
Sensors
Freescale Semiconductor
validcal: ldhx #N2
jsr wrflash
;burn N2 into flash
ldhx #msg05
;and display new current cal values from flash
jsr lcdstro
lda N1
;0mm value
jsr lcdbyto
lda #'/'
jsr lcdchro
lda N2
;160mm value
jsr lcdbyto
jsr del1s
jsr del1s
jmp nocalib
;done!
;__________________________________________________________
;__________________________________________________________
LEVEL: lda #$01
;===LEVEL=== main routine: displays level, flow & graphics
jsr lcdcmdo
;clear screen
lda #$0C
jsr lcdcmdo
;cursor off
lda #$88
;position cursor at LCD graphics portion
jsr lcdcmdo
;(2nd half of first line)
clra
;and write ascii $00 through $07
fillgfx: jsr lcdchro
;which contain the graphics related to
inca
;40 different readings
cmp #$08
;do all 8
bne fillgfx
LVL:
ldhx #ramfree
;point to 40 pressure readings
lda #$28
;count down from 40
purge: clr 0,x
;clear all those locations
incx
;next (H cannot change: we are in page0 RAM)
dbnza purge
jsr adcbyta
;get averaged A/D reading (i.e. NX)
jsr LfNx
;convert to level and
sta Lgfx
;store in "Level graphics"
LVLwarm: bset 4,porta
bset 5,porta
;LEDs on during this cycle
ldhx #ramfree
;point to 40 pressure readings
mov #$27,RA
;count down from 39
shiftgfx: lda 1,x
;take location+1
sta 0,x
;and move to location+0, i.e. shift graphics left
incx
;next X (once again: we are in page 0, no need to worry about H)
dbnz RA,shiftgfx ;do this 39x
jsr adcbyta
jsr LfNx
mov RA,OA
;get averaged A/D reading (i.e. NX)
;LX:=(NX-N1)*ConversionValue/(N2-N1)
;store result in OA
clr RB
;RB will contain graphic pixels (default=$00)
cmp UnitEmpt
;if <UnitEmpty (preset value = empty or almost)
bcs Lzero
;then "empty" (no pixels)
cmp UnitFull
;if >=UnitFull (preset value = full or almost)
bcc Lsat
;then "full" (pixel $80=bit 7)
clrh
;otherwise determine one of 8 graphic values
ldx UnitDiv
;UnitDiv is roughly full range/8
div
;in order to give 8 values
mov #$01,RB
;but now value has to be converted to pixel
AN1950
Sensors
Freescale Semiconductor
11
cmp #$01
;if result is $01
beq Lzero
;then display it directly
makeRB lsl RB
;otherwise shift 1 pixel bit to the right place
dbnza makeRB
;by counting down result of division
bra Lzero
Lsat: mov #$80,RB
;if full then position highest pixel
Lzero: lda RB
ldhx #ramfree+$27 ;last of the 40
sta 0,x
;put it at then end of the 40 bytes (new value), all others were shifted left
clr weath
;weath will contain dynamic change based also on value of RB
lda RB
beq donew
;if RB=$00 then weath=$00: "empty"
cmp #$80
bne notfull
;
mov #$01,weath ;if $80 then weath=$01: "full"
bra donew
notfull mov #$02,weath ;prepare for "steady" if L(i)=L(i-1)
lda OA
;get current level value L(i)
cmp Lgfx
;compare to previous level value L(i-1)
beq donew
mov #$03,weath ;"filling" if L(i)>L(i-1)
bcc donew
mov #$04,weath ;"emptying" otherwise
donew: lda OA
;current level L(i)
sub Lgfx
;minus previous level L(i-1)
sta MA
;establishes rate: L(i)-L(i-1)
mov RA,Lgfx
;update L(i-1)
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - golevel: lda #$80
;******** now let's display the level in decimal ********
jsr lcdcmdo
;start on 1st character of 1st line
lda OA
;get current level value
clrh
ldx #$64
;and divide by 100
div
bne over100
;if result is >0 then handle "hundreds"
lda #$20
;otherwise display space (remove leading 0)
jsr lcdchro
bra lnext
over100: jsr lcdnibo
;display "hundreds" digit
lnext: pshh
pula
;move remainder into A
clrh
ldx #$0A
;divide by 10
div
jsr lcdnibo
;display "tens" digit
lda #'.'
jsr lcdchro
;display decimal point
pshh
pula
jsr lcdnibo
;and first decimal
lda UnitType
;check for cm ($A0) vs. in (#3F)
cmp #$3F
beq dsplIN
dsplCM: lda #'c'
jsr lcdchro
lda #'m'
AN1950
12
Sensors
Freescale Semiconductor
jsr lcdchro
bra goflow
;display "cm" for centimeters
dsplIN: lda #'i'
jsr lcdchro
lda #'n'
jsr lcdchro
;display "in" for inches
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - goflow: lda #$C0
;******** now let's display the flow in decimal ********
jsr lcdcmdo
;position cursor on 1st character 2nd line
lda MA
;get flow
lsla
;test sign of rate (in MA)
bcc positiv
;if positive, then it's easy
lda MA
coma
inca
sta MA
cmp #$64
bcs not2lo
lda #'<'
jsr lcdchro
lda #$63
sta MA
bra goconv
;otherwise 1's complement of MB
;check to see if >100
;if not we are OK
;otherwise display that we exceeded min rate
;that LCD can display (<9.9)
;force value to 99
not2lo: lda #'-'
jsr lcdchro
bra goconv
positiv: lda MA
cmp #$64
bcs not2hi
lda #'>'
jsr lcdchro
lda #$63
sta MA
bra goconv
;display that minus sign
;check to see if >100
;if not we are OK
;otherwise display that we exceeded max rate
;that LCD can display (>9.9)
;force value to 99
not2hi: lda #'+'
jsr lcdchro
goconv: lda MA
clrh
ldx #$0A
div
jsr lcdnibo
lda #'.'
jsr lcdchro
pshh
pula
jsr lcdnibo
lda UnitType
cmp #$3F
beq dsplINf
;display the plus sign (to keep alignment)
;get flow
;and divide by 10
;display "tens" digit
;display decimal point
;and first decimal
;check for cm ($A0) vs. in (#3F)
dsplCMf: lda #'c'
jsr lcdchro
lda #'m'
bra reusef
AN1950
Sensors
Freescale Semiconductor
13
dsplINf: lda #'i'
jsr lcdchro
lda #'n'
reusef: jsr lcdchro
lda #'/'
jsr lcdchro
lda #'s'
jsr lcdchro
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - gfxupdt: lda #$40
;======== Graphics Update: tough stuff ===========
jsr lcdcmdo
;prepare to write 8 bytes into CGRAM starting at @ $40
ldhx#ramfree;point to 40 pressure readings (this reuses wrflash RAM)
mov #$08,DA
;DA will count those 8 CGRAM addresses
cg8:
lda 0,x
sta NC
lda 1,x
sta NB
lda 2,x
sta NA
lda 3,x
sta DC
lda 4,x
staDB;readings 0-4 go into NC,NB,NA,DC,DB and will form 1 LCD special
character
mov #$08,RA
;RA will count the 8 bits
fill:clrRB;start with RB=0, this will eventually contain the data for CGRAM
rol NC
rolRB
rol NB
rolRB
rol NA
rolRB
rol DC
rolRB
rol DB
rolRB;rotate left those 5 values and use carry bits to form RB (tough part)
lda RB
jsrlcdchro;and put it into CGRAM
dec RA
;do this 8 times to cover all 8 bits
bne fill
incx
incx
incx
incx
incx ;now point to next 5 values for next CGRAM address (5 values per
character)
dec DA
;do this for all 8 CGRAM characters
bne cg8
ldaweath;get weather variable and decide which message to display
cmp #$04
bne try3210
ldhx #msg02e
;if $04
bra showit
try3210: cmp #$03
bne try210
ldhx #msg02d
;if $03
bra showit
try210: cmp #$02
AN1950
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Sensors
Freescale Semiconductor
bne try10
ldhx #msg02c
;if $02
bra showit
try10: cmp #$01
bne try0
ldhx #msg02b
;if $01
bra showit
try0: ldhx #msg02a
;otherwise this one
showit: jsr lcdstro
jsr del1s
;1s between pressure/altitude readings
brset 1,porta,contin ;exit only if SEL
brset 2,porta,contin ;and ENT pressed together
jmp MENU
contin: jmp LVLwarm
;__________________________________________________________
LfNx: sub N1
;*** PX=f(NX,N2,N1) ***
ldx UnitType
;$A0=160 for cm, $3F=63 for in
mul
sta NA
stx NB
clr NC
;NCNBNA:=(NX-N1)* (conversion value: 160 or 63)
lda
sub
sta
clr
clr
jsr
N2
N1
DA
DB
DC
NdivD
;RBRA:=(NX-N1)*(conversion value)/(N2-N1)
lda RA
cmp #$C8
;check to see if result is negative
bcs noovflw
;if <$C8 we are OK
ovflw: clr RA
;otherwise force level to 0!
noovflw: lda RA
rts
;__________________________________________________________
NdivD: clr RA
;RBRA:=NCNBNA/DCDBDA
clr RB
;destroys NCNBNA and DCDBDA
keepatit: lda RA
add #$01
sta RA
lda RB
adc #$00
sta RB
;increment RB:RA
lda NA
sub DA
sta NA
lda NB
sbc DB
sta NB
lda NC
sbc DC
sta NC
;NC:NB:NA:=NC:NB:NA-DC:DB:DA
bcc keepatit
;keep counting how many times until overflow
lda RA
sub #$01
sta RA
lda RB
sbc #$00
sta RB
;we counted once too many, so undo that
AN1950
Sensors
Freescale Semiconductor
15
lsr DC
ror DB
ror DA
;divide DC:DB:DA by 2
lda NA
add DA
sta NA
lda NB
adc DB
sta NB
lda NC
adc DC
sta NC
;and add into NC:NB:NA
lsla
bcs nornd
;if carry=1 then remainder<1/2 of dividend
lda RA
add #$01
sta RA
lda RB
adc #$00
sta RB
;otherwise add 1 to result
nornd: rts
;__________________________________________________________
;__________________________________________________________
UNITS: brclr 2,porta,UNITS ;let go of ENT first
lda #$01
;===UNITS=== Allows user to select units: inches or cm
jsr lcdcmdo
;clear screen
ldhx
jsr
jsr
clr
lda
jsr
uluke:
#msg03
lcdstro
;Unit Choice menu
del100ms
RA
;menu choice=0 to begin with
#$0D
lcdcmdo
;blink cursor on menu choice
ldx RA
;get current menu choice
clrh
lda menupos,x
;and look up corresponding LCD address
jsr lcdcmdo
;reposition cursor
uwarm: brclr 1,porta,uPB1 ;check for SEL
brclr 2,porta,uPB2 ;or for ENT
bclr 4,porta
;otherwise
bset 5,porta
;turn on "SEL" LED
jsr del100ms
;delay
bset 4,porta
;toggle LEDs
bclr 5,porta
;"ENT" now on: means choice is SEL ***or*** ENT
jsr del100ms
;delay and repeat until SEL or ENT
bra uwarm
uPB1:
inc RA
;***SEL*** toggles menu choices
lda RA
cmp #$02
;menu choices are $00 and $01
bne uPB1ok
clr RA
;back to $00 when all others have been offered
uPB1ok: bclr 4,porta
bclr 5,porta
;LEDs off
jsr del100ms
;wait a little bit
brclr 1,porta,uPB1ok ;make sure they let go of SEL
bra uluke
AN1950
16
Sensors
Freescale Semiconductor
uPB2:
bclr 4,porta
;***ENT*** confirms menu choice
bclr 5,porta
;LEDs off
lda RA
;get menu choice
bne SelIN
SelCM: ldhx #$A014
;initialize default units to cm ($A0=cm, $3F=in)
sthx UnitType
;UnitType set to $A0; UnitDiv set to $14
ldhx #$039E
sthx UnitEmpt
;UnitEmpt set to $03; UnitFull set to $9E
lda #$01
jsr lcdcmdo
;clear LCD
ldhx #msg03a
jsr lcdstro
;and show choice selection to be cm
jsr del1s
;wait 1s
jmp LEVEL
;let's do LEVEL now...
SelIN:
ldhx #$3F08
;initialize default units to in ($A0=cm, $3F=in)
sthx UnitType
;UnitType set to $3F; UnitDiv set to $08
ldhx #$033D
sthx UnitEmpt
;UnitEmpt set to $03; UnitFull set to $3D
lda #$01
jsr lcdcmdo
;clear LCD
ldhx #msg03b
jsr lcdstro
;and show choice selection to be in
jsr del1s
;wait 1s
jmp LEVEL
;let's do LEVEL now...
;__________________________________________________________
;__________________________________________________________
;__________________________________________________________
;********************************************************************
;********************************************************************
;******** GENERAL Routines ******************************************
;********************************************************************
;********************************************************************
;-------- INITIALIZATION Routines ----------------------------------;
ALLINIT: initializes HC08, sets I/O, resets LCD and LEDs
;
------ALLINIT: bset 0,config1
;disable COP
mov #$38,ddra
;PTA0=MPAK,PTA1=SEL,PTA2=ENT,PTA3=E,PTA4=RS,PTA5=clk
mov #$30,adiclk ;ADC clock /2
bclr 3,porta
;E=0
bclr 4,porta
;grn=OFF; RS=0
bclr 5,porta
;red=OFF; CLK=0
rts
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
WARMUP: waits half a second while it flashes LEDs, and allows LCD to get ready
;
-----WARMUP: bclr 4,porta
bclr 5,porta
;LEDs off
lda #$0A
;prepare to do this 10x
tenx: jsr del25ms
;delay
bclr 4,porta
bset 5,porta
;alternate on/off
jsr del25ms
bset 4,porta
bclr 5,porta
;and off/on
dbnza tenx
;10 times so the LCD can get ready (slow startup)
jsr lcdinit
;now initialize it
AN1950
Sensors
Freescale Semiconductor
17
bclr 4,porta
bclr 5,porta
;LEDs off
rts
;-------- WRITE TO EEPROM Routines ---------------------------------;
wrflash: burns A into flash at location pointed by H:X
;
------wrflash: sthx flshadr
;this is the address in the flash
sta flshbyt
;and the byte we want to put there
tsx
sthx memSP
;store SP in memSP, so it can be temporarily used as a 2nd index register
ldhx #ramfree+1 ;SP now points to RAM (remember to add 1 to the address!!!, HC08 quirk)
txs
;SP changed (careful not to push or call subroutines)
ldhx #ersflsh
;H:X points to beginning of flash programming code
doall: lda 0,x
;get 1st byte from flash
sta 0,sp
;copy it into RAM
aix #$0001
;HX:=HX+1
ais #$0001
;SP:=SP+1
cphx #lastbyt
;and continue until we reach the last byte
bne doall
ldhx memSP
;once done, restore the SP
txs
jsr ramfree
;and run the subroutine from RAM, you cannot write the flash while
rts
;running a code in it, so the RAM has to take over for that piece
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;*************** THE FOLLOWING CODE WILL BE COPIED INTO AND WILL RUN FROM RAM ******
ersflsh: lda #$02
;textbook way to erase flash
sta flcr
lda flbpr
clra
ldhx flshadr
sta 0,x
bsr delayf
lda #$0A
sta flcr
bsr delayf
lda #$08
sta flcr
bsr delayf
clra
sta flcr
bsr delayf
pgmflsh: lda #$01
;textbook way to program flash
sta flcr
lda flbpr
clra
ldhx flshadr
sta 0,x
bsr delayf
lda #$09
sta flcr
bsr delayf
lda flshbyt
ldhx flshadr
sta 0,x
bsr delayf
lda #$08
sta flcr
bsr delayf
clra
sta flcr
AN1950
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Sensors
Freescale Semiconductor
bsr delayf
rts
delayf: ldhx #$0005
;wait 5x20us
mov #$36,tsc
;stop TIM & / 64
sthx tmodh
;count H:X x 20us
bclr 5,tsc
;start clock
delayfls: brclr 7,tsc,delayfls
rts
;this RTS will move from RAM back into EEPROM
lastbyt: nop
;*************** END OF CODE THAT WILL BE COPIED INTO AND WILL RUN FROM RAM ******
;-------- DELAY Routines -------------------------------------------;
del1s: generates a 1s delay
;
----del1s: pshh
pshx
ldhx #$C350
;1 second delay=$C350=50000 x 20us
bra delmain
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
del100ms: generates a 100ms delay
;
-------del100ms: pshh
pshx
ldhx #$1388
bra delmain
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
del50ms: generates a 50ms delay
;
------del50ms: pshh
pshx
ldhx #$09C4
bra delmain
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
del25ms: generates a 25ms delay
;
------del25ms: pshh
pshx
ldhx #$04E2
bra delmain
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
del5ms: generates a 5ms delay
;
-----del5ms: pshh
pshx
ldhx #$00FA
bra delmain
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
del1ms: generates a 1ms delay
;
-----del1ms: pshh
pshx
ldhx #$0032
bra delmain
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
del100us: generates a 100us delay
;
----del100us: pshh
pshx
ldhx #$0005
bra delmain
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
AN1950
Sensors
Freescale Semiconductor
19
;
delmain: main delay routine; generates delay equal to H:X x 20us
;
------delmain: mov #$36,tsc
;stop TIM & / 64
sthx tmodh
;count H:X x 20us
bclr 5,tsc
;start clock
delwait: brclr 7,tsc,delwait ;wait for end of countdown
pulx
pulh
rts
;this RTS serves for all delay routines!
;-------- A/D Routines ---------------------------------------------;
adcbyti: gets single A/D reading from PTA0 and returns it in A
;
------adcbyti: mov #$00,adscr ;ADC set to PTA0
brclr 7,adscr,*
;wait for ADC reading
lda adr
;result in adr
rts
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
adcbyta: gets averaged A/D reading from PTA0 and returns it in A
;
------adcbyta: clr CNT
;average 256 readings
clr RB
;will be addint them up
clr RA
;in RB:RA
do256a: bsr adcbyti
add RA
sta RA
lda RB
adc #$00
sta RB
;16-bit add into RB:RA
dbnz CNT,do256a ;do all 256
lsl RA
;if RA<$80
bcc nochga
;then RB result is correctly rounded
inc RB
;otherwise round off to next value
nochga: lda RB
rts
;-------- LCD Routines ---------------------------------------------;
lcdinit: initializes LCD
;
------lcdinit: lda #$3C
;set 8-bit interface, 1/16 duty, 5x10 dots
bsr lcdcmdo
lda #$0C
;display on, cursor off, blink off
bsr lcdcmdo
lda #$06
;increment cursor position, no display shift
bsr lcdcmdo
lda #$01
;clear display
bsr lcdcmdo
rts
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
lcdcmdo: sends a command to LCD
;
------lcdcmdo: bsr shiftA
bclr 4,porta
;RS=0 for command
bset 3,porta
bclr 3,porta
;toggle E
bsr del5ms
;some commands require 2ms for LCD to execute
rts
;so let's play it safe
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
lcdchro: sends a character (data) to LCD
;
------lcdchro: bsr shiftA
bset 4,porta
;RS=1 for data
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20
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bset 3,porta
bclr 3,porta
;toggle E
bsr del100us
;data only requires 40us for LCD to execute
rts
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
shiftA: shifts A into shift register and provides 8-bits to LCD
;
-----shiftA: psha
mov #$08,BB
;will be shifting 8 bits
all8: lsla
;get bit
bcc shift0
;if bit=0 then shift a 0
shift1: bset 4,porta
;otherwise shift a 1
bra shift
shift0: bclr 4,porta
;bit 4 is data to shift register
shift: bclr 5,porta
;bit 5 is shift register clock
bset 5,porta
bclr 5,porta
;toggle CLK
dbnz BB,all8
;do all 8 bits
pula
rts
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
lcdnibo: displays 1 character (0-9,A-F) based on low-nibble value in A
;
------lcdnibo: psha
;convert 4 bits from binary to ascii
add #$30
;add $30 (0-9 offset)
cmp #$39
;is it a number (0-9) ?
bls d0to9b
;if so skip
add #$07
;else add $07 = total of $37 (A-F offset)
d0to9b: bsr lcdchro
pula
rts
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
lcdbyto: displays 2 characters based on hex value in A
;
------lcdbyto: psha
psha
;remember A (for low nibble)
lsra
;shift right 4 times
lsra
lsra
lsra
bsr lcdnibo
;high nibble
pula
and #$0F
bsr lcdnibo
;low nibble
pula
rts
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;
lcdstro: displays message ending in '@', but also sends commands to LCD
;
------lcdstro: psha
lda 0,x
lcon: cmp #$80
;if ASCII >=$80
bhs iscmd
cmp #$1F
;or <=$1F then
bls iscmd
;assume it is a command to LCD
isdta: bsr lcdchro
;otherwise it is data to LCD
reuse1: aix #$0001
;next character
lda 0,x
;indexed by x
cmp #$40
;continue until
bne lcon
;character = '@'
AN1950
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21
pula
;we are done
bclr 4,porta
;so
bclr 5,porta
;turn off LEDs
rts
iscmd: bsr lcdcmdo
bra reuse1
;-------- ROM DATA: contains all LCD messages ----------------------msg01 db $01,$80,'*MPAK & 908QT4* '
db
$C0,'Reference Design','@'
msg01a db $01,$80,'Water Level & '
db
$C0,'Flow
v2.0','@'
msg01b db $01,$80,'1:Level/Flow '
db
$C0,'2:Set Units ','@'
msg05 db $01,$80,'* Calibration! *'
db
$C0,'Curr lo/hi:','@'
msg05a db $01,$80,'1st point: 0mm'
db
$C0,'SEL:cal ENT:quit','@'
msg05b db $01,$80,'Calibrating... '
db
$C0,' 0mm: ','@'
msg05c db $01,$80,'2nd point: 160mm'
db
$C0,'ENT:continue ','@'
msg05d db $01,$80,'Calibrating... '
db
$C0,' 160mm: ','@'
msg05e db $01,$80,'INVALID
'
db
$C0,'CALIBRATION! ','@'
msg02a db
$C8,' EMPTY','@'
msg02b db
$C8,' FULL','@'
msg02c db
$C8,' steady','@'
msg02d db
$C8,' H20 in','@'
msg02e db
$C8,' H20 out','@'
msg03 db $01,$80,'1: unit=cm H20 '
db
$C0,'2: unit=in H20 ','@'
msg03a db
$80,'Unit is now: cm','@'
msg03b db
$80,'Unit is now: in','@'
menupos db $80,$C0
end
REFERENCES
Baum, Jeff, “Frequency Output Conversion for MPX2000
Series Pressure Sensors,” Application Note AN1316/D.
Hamelain, JC, “Liquid Level Control Using a Pressure
Sensor,” Application Note AN1516/D.
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NOTES
AN1950
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23
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AN1950
Rev. 4
11/2006
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