ECE Homework #3

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Coleen Long
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1 ECE Homework #3 Flow Charts, Binary Inputs, Binary Outputs (LEDs). Due Monday, January 29th The temperature sensor in your lab kits has the temperature-resistance relationship of R = 1000 exp T 298 Ω where T is the temperature in degrees Kelvin (C + 273) 1) Design a circuit which outputs 0V when the temperature is below 0C when the temperature is above 0C At 0C, R = 3381Ω Assume a voltage divider with a 3300 Ohm resistor. Then V = R R+3300 As temperature goes up... = V R goes down Vin goes down Vout goes up Connect the divider to the - input Connect V to the + input V MCP602 Y R Vin 0V 0V 2.53V Hot 0C Cold

2 2) Design a circuit with hysteresis which outputs 0V when the temperature goes below 0C and when the temperature goes above 5C Assume a voltage divider with a 3300 Ohm resistor like problem #1 At 0C R = 3381 Ohms Vin = V Vout goes low At 5C R = 2604 Ohms Vin = Vout goes high As Vin goes low, Vout goes high. Connect the voltage divider to the - input The gain you need is gain = V out V in gain = 0V V = When the output is 0V, you switch at Set the + input to k 3300 Vin 2.20V 10k Y Vout R 10k Vin 0V 0V 2.20V 2.53V 153k hot 5C 0C cold

3 The characteristics for a piranha RGB LED is Red: Vf = 20mA 10,000 20mA Green: Vf = 20mA 10,000 20mA Blue: Vf = 20mA 10,000 20mA 3) Design a circuit so that the PIC can turn on and off each LED at 20mA. Assign the I/O pins to: RC0: Red RC1: Green RC2: Blue Red Green Blue R r = 1.8V 20mA = 160Ω R g = 3.0V 20mA = 100Ω R b = 3.0V 20mA = 100Ω RC2 RC1 RC0 anode Rb Rg Rr cathode 3.0V 3.0V 1.8V blue green red Piranah Package common cathode + cathode + 3.0V - + blue 3.0V green 1.8V red anode Rb Rg Rr RC2 RC1 RC0 Piranah Package common anode

4 The following program turns your PIC into an multi-function flashlight: Requirements: Input: Buttons RB0.. RB5 Output: Piranha RGB LED connected to pins RC0..RC1 Relationship: When you press a button, the color changes to: RB0: All colors off RB1 Red RB2 Green RB3 Blue RB4 White (R, G, B all on) RB5: Random color "On" is defined as 20mA +/- 5mA. Analysis:

5 4) Write an assembler program to implement this LED flashlight #include <p18f4620.inc> COLOR equ 0 ; Start of code: org 0x800 clrf TRISA movlw 0xFF movwf TRISB clrf TRISC clrf TRISD clrf TRISE clrf COLOR movlw 0x0F movwf ADCON1 Main: movf COLOR, W btfsc PORTB,0 ; off movlw 0 btfsc PORTB,1 ; red movlw 1 btfsc PORTB,2 ; green movlw 2 btfsc PORTB,3 ; blue movlw 4 btfsc PORTB,4 ; white movlw 7 btfss PORTB,5 ; random goto Output Random: addlw 1 btfsc PORTB,5 goto Random andlw 0x07 Output: movwf COLOR movff COLOR, PORTC goto Main RB0 RB1 RB2 Start Initialize PORTC = Input PORTC = Output Recall Present Color Button Pressed? none Off Red Green Blue White Random Output Color to PORTC RB3 RB4 RB5 end Compilation Results: Loaded C:\Documents and Settings\Administrator\My Documents\ECE376\Assembler\Flashlight.cof. Debug build of project `C:\Documents and Settings\Administrator\My Documents\ECE376\Assembler\1234.mcp' succeeded. Language tool versions: MPASMWIN.exe v5.51, mplink.exe v4.49, mplib.exe v4.49 Preprocessor symbol ` DEBUG' is defined.mon Jan 22 07:00: BUILD SUCCEEDED

6 If you look at the.lst file: LOC OBJECT CODE VALUE LINE SOURCE TEXT #include <p18f4620.inc> LIST ;========================================================================== ; MPASM PIC18F4620 processor include ; ; (c) Copyright Microchip Technology, All rights reserved ;========================================================================== LIST COLOR equ ; Start of code: org 0x A clrf TRISA EFF movlw 0xFF E movwf TRISB A clrf TRISC A clrf TRISD 00080A 6A clrf TRISE 00080C 6A clrf COLOR E 0E0F movlw 0x0F EC movwf ADCON Main: movf COLOR, W B btfsc PORTB, E movlw B btfsc PORTB, A 0E movlw C B btfsc PORTB, E 0E movlw B btfsc PORTB, E movlw B btfsc PORTB, E movlw AA btfss PORTB, A EF1C F goto Output 00082E Random: 00082E 0F addlw BA btfsc PORTB, EF17 F goto Random B andlw 0x Output: E movwf COLOR 00083A C000 FF movff COLOR, PORTC 00083E EF09 F goto Main MPASM 5.51 FLASHLIGHT.ASM :00:45 PAGE 2

7 If you look at the.hex file : FA : AFF0E936E946A956A966A006A0F0E5A : C16E005081B0000E81B2010E81B4020E93 : B6040E81B8070E81AA1CEF04F0010FF7 : BA17EF04F0070B006E00C082FF09EFCA : F0C2 : FF That's your program. It taks 29 lines of assembler to make a flashlight. Validation: 5) Compile and download your code to your PIC board. Collect data to verify that you met the requirements: The current through each color is 20mA +/- 5mA Each button changes the output color RB5 produces a 'random' color (i.e. a random number from 0 to 7 is output to PORTC when you release RB5)

8 6) For your resulting program... How long does it take your program to loop? (toggle a bit you're not using, such as RC4, in the main loop. Check on the oscilloscope how fast this bit is toggling). How many lines of assembler does it take to implement an LED flashlight?

Flow Charts and Assembler Programs

Flow Charts and Assembler Programs Flow Charts: A flow chart is a graphical way to display how a program works (i.e. the algorithm). The purpose of a flow chart is to make the program easier to understand.