Physical Computing Quick Reference for the PIC (18F452)

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Digital Input 

' 
in PicBasic Pro, we need these lines at the top of our program ' to set the pin 
that we're debugging on, and the baud rate at which ' to send debug messages: 
INCLUDE "modedefs.bas" DEFINE DEBUG_REG PORTC DEFINE DEBUG_BIT 6 DEFINE DEBUG_BAUD 
9600 DEFINE DEBUG_MODE 1 ' declare a variable called X: X var byte ' make pin 
B0 an input pin: Input portb.0 Main: ' read the value of pin B0 into the variable 
X: X = portB.0 Debug ["X = ", DEC X, 10, 13] Goto main

 

Digital Output

Flashing Led
 
Relays for turning anything on and off. Used most commonly with AC power. 
Transistor Circuit for turning on and off DC devices.
  

' Put pins into input mode: input 
portB.0 input portB.1 input portB.2 MyLoop: ' turn off the "switches off" LED: 
Low portC.1 'if all the switches are on then turn off the "switches off" LED ' 
and go to the flash routine: if portb.0 = 1 and portb.1 =1 and portb.2 = 1 then 
' Turn on the flashing LED, and turn off the "switches off" LED: High portC.2 
Low portc.1 Pause 100 ' flash the flashing LED: Low portC.2 Pause 100 High portC.2 
Pause 100 Low portC.2 else ' if any switches is not on, turn on the "Switches 
off" LED: High portC.1 ' turn off flashing LED: Low portC.2 endif Goto MyLoop

 

Analog Input

Standard ADC Input Circuit for use with any variable resistor with two leads

ADC Circtuit for use with a pot.
  

' 
Set Debug pin port DEFINE DEBUG_REG PORTCB ' Set Debug pin BIT DEFINE DEBUG_BIT 
6 ' Set Debug baud rate DEFINE DEBUG_BAUD 9600 ' Set Debug mode: 0 = true, 1 = 
inverted DEFINE DEBUG_MODE 1 ' Define ADCIN parameters DEFINE ADC_BITS 10 ' Set 
number of bits in result DEFINE ADC_CLOCK 3 ' Set clock source (3=rc) DEFINE ADC_SAMPLEUS 
20 ' Set sampling time in uS ' declare a variable to hold the result: ADCVar var 
word TRISA = %11111111 ' Set PORTA to all input ADCON1 = %10000010 ' Set PORTA 
analog and right justify result Pause 500 ' Wait .5 second main: ' read ADC channel 
0: adcin 0, ADCVar ' debug the raw value (the value 13 makes the return): debug 
"ADCVar: ", DEC ADCVar, 13, 10 GoTo main
RC Circuit for use with variable resistors. You would use this if your microcontroller does not have ADC capabilities or you you have run out of ADC pins. 
' 
since RCTime doesn't depend on an ADC, we can use any pin. ' This example uses 
pin B0: ' Set Debug pin port DEFINE DEBUG_REG PORTB ' Set Debug pin BIT DEFINE 
DEBUG_BIT 6 ' Set Debug baud rate DEFINE DEBUG_BAUD 9600 ' Set Debug mode: 0 = 
true, 1 = inverted DEFINE DEBUG_MODE 1 ' set up a variable to hold the result: 
RCVar var word Main: ' Take pin 0 high to discharge capacitor: high portB.0 ' 
hold 1 millisecond to make sure capacitor is discharged pause 1 ' Measure time 
it takes to charge again. Rctime portB.0,1,RCVar ' debug the result: debug "RCVar: 
", DEC RCVar, 10, 13 goto main

 

Analog Output

For Dimming an LED. Doesn't work very well.
' 
the LED to be dimmed on pin RC3. period var byte output portc.3 main: for period 
= 0 to 255 ' pulse LED (pulsout 1 = 2 microseconds) pulsout portc.3, period ' 
pause in microseconds; ' pause time gets longer as pulse gets shorter ' pauseus 
pauses for microseconds, not milliseconds: pauseus 2*(255 - period) next
 
goto main
Tone Generation

 
' 
declare an array of 12 word variables: pitch var word(12) ' declare other variables: 
note var byte ADCVar var word thisNote var word ' the 12 elements of the array 
called pitch are the 12 notes of a scale: pitch(0) = 262 ' middle C pitch(1) = 
277 ' C# pitch(2) = 294 ' D pitch(3) = 311 ' D# pitch(4) = 330 ' E pitch(5) = 
349 ' F pitch(6) = 370 ' F# pitch(7) = 392 ' G pitch(8) = 415 ' G# pitch(9) = 
440 ' A pitch(10) = 466 ' A# pitch(11) = 494 ' B main: For note = 0 to 11 ' so 
we put the pitch into a normal word variable: thisNote = pitch(note) ' play note: 
freqout portc.4, 1000, thisNote, thisNote next goto main
RC Servo Motor
' 
the servo is on pin C3 ' note: if you use a crystal other than 4MHZ, ' it changes 
the pulsewidth of pulsout. ' For a 20MHZ crystal, for example, pulsout is five 
times as ' fast, so you'd need to multiply the pulse widths by 5 ' with a 20 Mhz 
crystal. DEFINE OSC 4 angleVar VAR word ' set up constants with the minimum and 
maximum pulse widths minAngle con 50 maxAngle con 250 ' set up a constant with 
the time between pulses: refreshPeriod con 20 ' set an initial pulsewidth: angleVar 
= minAngle main: 'take the output pin low so we can pulse it high Low portc.3 
' pulse the pin PulsOut portc.3, angleVar ' pause for as long as needed: pause 
refreshPeriod ' change the angle for the next time around: if angleVar > maxAngle 
Then angleVar = minAngle else angleVar = angleVar + 1 endif GoTo main

Serial Connections

Programming your chip

 

 

Having your program talk to other computers.

Power Connections

These are pinouts for a 7508 +5Volt Voltage Regulator. Necessary for the PIC.Decoupling your power supply by adding these two capacitors will smooth out the flow which is important when you are using things like motors and not a bad idea in general

 

ASCII Highlights

0) NULL33) !41) }48) 055) 765) A
7) BELL34) "42) *49) 1 56) 890) Z

9) TAB

35) #43) +50) 2 57) 991) [

10) LF LineFeed

36) $44) ,51) 3 58) :92) \
13) CR Carriage Return37) %45) _52) 4 60) <97) a
27) ESCAPE38) &46) .53) 5 61) =122) z
32) SPACE 39) '47) /54) 6 63) ?127) DEL

Schematic
Highlights

Pinout Abbreviations

+Voltage:Vdd, Vin, Vcc, V+
Ground: VSS, VEE, Gnd

Transmit: TX
Receive: RX

Oscillator:OSC
Reset: RES, MCLR

(A line over an abbreviation means connection to ground to make it happen)

Chip Select: CS
Master Out, Slave In: MOSI
Master In, Slave Out: MISO
Clock: CLK, SCLK, SCL
Serial Data Input: SDI
Serial Data Output: SDO

 

Capacitor Markings
CodeMicrofarads
1020.001
1030.01
1040.1
1051

 

Resistor Stuff

Color ValueMultiplier
Black0x1
Brown
1x10
Red2x100
Orange3x1k
Yellow4x10k
Green5x100k
Blue6x1M
Violet7x10M