Using PICAXE with Inputs Using PICAXE with Analog Inputs Using PICAXE
Document Sample
Using PICAXE with Inputs
You can also use inputs with a PICAXE. Here we use a simple top switch block. The
switch is in a potential divider circuit so that the output of the block is normally held low
(zero), but when the switch is pressed the block’s output goes high (one). You can test
this with the PICAXE. The switch is on input pin 1.
main: if input1=1 then light ‘ if switch pressed jump
low 4 ‘ make sure LED is off
goto main ‘ do it again
light: high 4 ‘ new label – turn LED on
goto main ‘ check switch again
Here is another program which flashes a different LED depending on whether the switch
is pressed.
main: if input1=1 then flash1 ‘ jump if input is high
high 7 ‘ output 7 on
goto flash7
flash1: high 1 ‘ output 1 on
flash7: pause 200 ‘ wait 0.2 seconds
let pins=%00000000 ‘ turn all outputs off
pause 200 ‘ wait 0.2 seconds
goto main ‘ jump back to start
Using the 7 segment display can you create a circuit which counts the number of times
the switch is pressed? Here is the first part:
init: symbol count = b0 ‘ set up an alias
count = 0 ‘ start count at zero
main: if input1 = 1 then add1 ‘ jump if key pressed
pause 50 ‘ give key time to settle
... ‘ you do the rest!
Using Analog Inputs
You can use standard sensor blocks with any
PICAXE input, perhaps using a comparator to set
the switching level. However a PICAXE 18 has
analog inputs on pins 0, 1 and 2. Connecting directly
to the core block will use pin 1. If you put the
sensing block before one of the 4 key units then the
input will be on pin 2.
main: readadc 1,b0 'read input 1 into b0
debug b0 'send value to computer
b1=b0/20 'change into 8 levels
if b1<8 then skip
b1=7
skip: let pins=0 'turn current LED off
high b1 'show value on 8 LEDs
goto main
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The following code reads the light sensor on pin 2 and displays the result on the
LCD display. Analog input is low resolution for PICAXE18 and high resolution for
18A.
init: pause 500
main: readadc 2,b1
serout 4,N2400,(254,128,"Input 2 is ",#b1," ") 'show number
pause 200
goto main
This code takes an analog input and displays it as 8 levels on LEDs.
main: readadc 1,b0 'read input 1 into variable b0
debug b0 'check value on computer
b1=b0/20 'change into 8 levels
if b1<8 then skip
b1=7
skip: let pins=0 'turn current LED off
high b1 'show value on 8 LEDs
goto main
This program sets two LEDs according to the analog input.
main: readadc 1,b0 'read channel 2 into variable b0
debug b0
if b0 > 90 then top 'if b0 > 90 then do top
if b0 < 50 then bot 'if b0 < 50 then do bot
low 1 'else switch off 1
low 2 'and switch off 2
goto main 'jump back to the start
top: high 1 'switch on 1
low 2 'switch off 2
goto main
bot: high 2 'switch on 2
low 1 'switch off 1
goto main
Instead of an LDR you could use a thermistor or potentiometer input.
Using the DS18B20 Temperature Sensor
This Dallas One-Wire sensor provides the
temperature in degrees centigrade when
interrogated by the PICAXE ReadTemp instruction.
Here is a simple example displaying the result on an
LCD screen. The pcb passes 4 inputs through to a
preceding block.
loop: pause 500
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readtemp 1,b1
if b1>127 then neg
serout 4,N2400,(254,128,"Temp is ",#b1," ")
goto loop
DS18B20
neg: let b1=b1-128
serout 4,N2400,(254,128,"Temp is ","-",#b1," ")
goto loop
Using an Infra-red Remote Control
You can use a TSOP1836 device to receive signals
from an ordinary remote control. As long as it uses the
standard RC5 coding system then the Picaxe can
understand it using Infrain and Infra commands. The
first program turns LEDs on and off depending on
which keys on the remote are pressed. The pcb looks
more complicated than it is really because it passes
through 4 of the inputs.
loop: infrain ‘always uses pin 0
if infra = 1 then swon1
if infra = 2 then swon2
if infra = 3 then swon3 330R 4k7
if infra = 4 then swoff1 TSOP
1840
if infra = 5 then swoff2
if infra = 6 then swoff3
goto loop
swon1: high 1
goto loop
swon2: high 2 Key Value
goto loop 1 1
swon3: high 3
2 2
goto loop
swoff1: low 1 3 3
goto loop 4 4
swoff2: low 2 5 5
goto loop 6 6
swoff3: low 3 7 7
goto loop 8 8
9 9
This program takes the key press and displays it on an LCD P+ 10
display. It would need extending to display more keys. 0 11
V+ 12
init: pause 500 P- 13
loop: let pins=0 ‘clear outputs
10+ 14
infrain V- 15
if infra = 1 then swon1 Mute 16
if infra = 2 then swon2 Power 17
if infra = 3 then swon3
goto loop
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swon1: high 1
serout 4,N2400,(254,128,"Key pressed ",#1," ")
goto loop
swon2: high 2
serout 4,N2400,(254,128,"Key pressed ",#2," ") ‘show number
goto loop
swon3: high 3
serout 4,N2400,(254,128,"Key pressed ",#3," ")
goto loop
The next program uses the P+ and P- keys (along with V+ and V-) to set the level
of two variables and display them on the LCD.
symbol P = b0
symbol V = b1
init: pause 500 'allow LCD to initialise
serout 4,N2400,("Ready")
P=50 'initial value set half way
V=50
main: infrain
if infra=10 then increaseP 'P+
if infra=13 then decreaseP 'P-
if infra=12 then increaseV 'V+
if infra=15 then decreaseV 'V-
goto main
increaseP: if P=100 then display '100 is max possible value
P=P+1
goto display
decreaseP: if P=1 then display '1 is minimum value
P=P-1
goto display
increaseV: if V=100 then display
V=V+1
goto display
decreaseV: if V=1 then display
V=V-1
display: serout 4,N2400,(254,128,"P is set at ",#b0," ")
serout 4,N2400,(254,192,"V is set at ",#b1," ")
goto main
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Shared by: Jun Wang
Jun Wang
Prof.
Dr
China Agricultural ...
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