Transcript Some “facts” about software…

Embedded Systems
Introduction to Circuit Design
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Hardware/Circuit Design
• You won’t be a circuit designer upon completion
of this class
– You will [hopefully] become comfortable working
around hardware circuits
– This is how software engineers become circuit
designers, albeit sometimes bad ones
• More often than not, we become system integrators
– Conversely, working with software is how hardware
engineers become programmers, albeit sometimes bad
ones
• We will consider the basics
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Hardware/Software Integration
• We will be studying hardware/software
integration using the Basic Stamp
development board
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The Basics
(no pun intended)
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Electo-Static Discharge (ESD)
• Static electricity
– It’s the shock you get when rubbing your feet across the
carpet then touching the person next to you
– It can destroy electronic components
• Ideally we work with hardware in a static safe lab
– we are not working in an ideal situation here
• Therefore, prior to working with hardware you
should touch a metal, grounded object prior to
touching the hardware
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Power
• Make sure the power is OFF (unplugged)
when you are putting components onto the
board!!!
• Check your work carefully prior to
supplying power to the board
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Supply Voltage
• Vdd – equivalent to the “+” terminal of a
battery (Voltage Drain Drain)
• Vss – equivalent to the “-” terminal of a
battery (Voltage Source Source)
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Solderless Breadboard
(Proto Board)
• This is used to create circuits without
having to solder parts or have special boards
manufactured, thus the name
– Used for prototyping circuits, thus the alternate
name
• Rows on either side of the vertical center
are connected together and thus are
considered a SINGLE connection
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Solderless Breadboard
(Proto Board)
These 5 holes are
connected together
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Resistor
• Resists the flow of electrical current
– Some components don’t like a lot of electrical current
– Creates a voltage drop across the resistor
– Ohm’s Law: V = IR
• Amount of resistance is specified in ohms, “Ω”
– Resistors come in many values
• Two leads (legs)
• Resistors are bidirectional
– It doesn’t matter which way you insert them into the
circuit
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Resistor
First 3 color bands represent the value in ohms
Last color band represents the accuracy in percentage
Schematic symbol
470 Ω
See: http://www.ealnet.com/m-eal/resistor/resistor.htm
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Light Emitting Diode (LED)
• One way current valve
• Important to insert them in the proper
direction
• Color means nothing in terms of circuit
connection
• Two leads (legs)
– Anode (labeled “+”)
– Cathode
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Light Emitting Diode (LED)
Cathode
Anode
+
Schematic symbol
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Push Button
• Simple input device
• Four leads (legs)
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Push Button
1,2
3,4
When not pressed, 1
is connected to 4 and
2 is connected to 3
1,3
2,4
1,4
2,3
Schematic symbol
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1
4
2
3
When pressed, the 1
is connected to 2 and
3, and 4 is connected
to 2 and 3
Speaker
Piezoelectric Speaker
(beeper)
Schematic symbol
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Activity
• Create a [very] simple circuit (see next slide)
• DO NOT APPLY POWER UNTIL YOU ARE
DONE CONNECTING UP THE CIRCUIT!!!
• This one requires no software
• Board have a 3-way power switch
– Position 0 – off
– Position 1 – on but only to circuits
– Position 2 – on to circuits and servo drivers
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A Simple Circuit
Vdd
Vss
470 Ω
One lead from
each component
plugged into
same row
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Ice Breaker
• Build the following three circuits on the
proto-board
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Ice Breaker Circuits/No Code
Vdd
Vss
470 Ω
Vdd
Vss
1,4
2,3
470 Ω
1,4
Vdd
2,3
Vss
470 Ω
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Circuits and Code
P9
Vss
470 Ω
HIGH 9
PAUSE 2500
LOW 9
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Circuits and Code
Vdd
P9
1,4
220 Ω
2,3
10k Ω
DO
DEBUG ? IN9
PAUSE 250
LOOP
btnpin VAR Byte
btnwrk VAR Byte
btnpin = 9
Main:
PAUSE 5
BUTTON btnpin, 0, 200, 20, btnwrk, 0, No_Press
DEBUG "*"
Vss
No_Press:
GOTO Main
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Circuits and Code
P9
Vss
FREQOUT 9, 1500, 2000
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Development Environment
• The Basic integrated development
environment (IDE) has been installed on all
computers
– Parallax group in Start menu
• If you are doing this at home (or laptop) you
should download the latest Basic Stamp
IDE from www.parallax.com
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Assignment – The “wordy” version
•
•
•
Two buttons (call them B1 and B2)
Three LEDs,1 yellow, 1 red, 1 green (call them Y, R, and G)
System specification
–
Start in “home position”
–
Press B1 one time
•
•
•
•
•
–
Press B2 one time – flash R slow
Press B2 two times in succession – flash R medium
Press B2 three times in succession – flash R fast
Press B1 – return to “home position”
Press B1 three times in succession
•
•
•
•
–
Press B2 one time – flash Y slow
Press B2 two times in succession – flash Y medium
Press B2 three times in succession – flash Y fast
Press B1 – return to “home position”
Press B1 two times in succession
•
•
•
•
–
LEDs off
Press B2 one time – flash G slow
Press B2 two times in succession – flash G medium
Press B2 three times in succession – flash G fast
Press B1 – return to “home position”
Press B1 four times in succession
•
•
•
Press B2 one time – flash LEDs in order Y-R-G-Y-R-G-…
Press B2 two times in succession – flash LEDs in order G-R-Y-G-R-Y-…
Press B1 – return to “home positin”
Notes
• “one time”, “two times”, “three times” means
button presses in “rapid” succession
• So for example
– <home - all LEDs off>, B1 <pause>, B2-B2 <pause>,
<Y flashes at medium speed>, B1, <home - all LEDs
off>
– <home - all LEDs off>, B1-B1-B1 <pause>, B2
<pause>, <G flashes at slow speed>, B2 <nothing
changes – G continues to flash at slow speed>, B1,
<home - all LEDs off>
Deliverables
• A state-machine diagram depicting the
operation of the system
• Source code
• A schematic diagram of the circuit
• A working demonstration on the Basic
Stamp development board (in class)