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PICList Project

Andrew D. Vassallo's Simon game.

This is based on an old handheld electronic game "Simon." Through 4 pushbutton switches, the user attempts to mirror an increasingly difficult sequence of blinking LEDs and speaker tones. Upon successful game completion (of 63 moves), the game sounds a cycling series of tones. Upon failed input at any point in the game, the correct move will be displayed, the error tone will sound, and then the maximum move number reached is sounded out on the speaker: first, low tones will sound the "tens" and then a higher tone will sound the "ones." So, for 12 moves reached, one single low tone will sound followed by two higher tones.

Each move is stored in memory and matched against 4 user input switches. The "moves" generated by the program are obtained from the TMR0 register at the time of the last user input, preventing the user from intentionally pushing a switch at a specific time to generate a predictable LED turn-on.

Each "move" is recorded in EEPROM data memory, 1 "move" per memory register (since location 0x00 isn't used, we really only have 63 moves possible). Upon mismatch of a switch input from the user and a recorded (expected) "move," the correct LED will turn on while a buzzer sounds the error tone. Also, if the user takes more time than allowed (~5 seconds), the timeout will indicate failed match. Note that if the user waits 4.9 seconds to press the button, then he has another 4 seconds to release it, as TMR_Overflow is reset. This gives a total of 10 seconds time to think between moves if the user is really careful.

(Note: It is possible to fit 4 "moves" per register (shifted in) to maximize the storage capacity at 252 moves, but at this point, 63 moves are enough. If anyone wants to try to increase this to 126 moves (swap the moves into the storage registers) or more (up to 252 moves by shifting the 2 LED bits), go right ahead. I wrote the core of this in a day, and added some options later, so there's probably some room for improvement. On the other hand, if you can remember more than 63 moves in sequence, you probably shouldn't be playing this game :)

Note the use of TMR0 interrupts to generate the different tones. This effectively allows continuous asynchronous control of switch input polling and speaker oscillation. I tried to comment this as completely as possible to help out those new to PIC programming. If there's something you don't understand, drop me an e-mail and I'll try to help.


If anyone does build one of these, I would be happy to hear about it. Please send me an e-mail at

Included is a very nice schematic with included recommended parts. For the piezo speaker, what I did was to scavenge one from an old internal computer modem that I had laying around. What is needed is an externally driven piezo buzzer. The specified P9924-ND speaker from Digi-Key ( works great, and it's only ~$2. You can also use a regular 7 or 8 ohm miniature audio speaker if you are careful to limit the current with a 100 ohm series resistor. Any momentary switches would work, too, but the ones recommended have a larger profile with a good sized button surface. Just build it up on perfboard or, like I did, a project box with included perfboard from Radio Shack for $4.00.

To get the +5V supply, you can use 4 AAA batteries if you like, or a couple of 3V lithium coin cells, a 6V "N" size battery, or a 4.8V rechargeable NiCD pack. Or, you can make a voltage regulator circuit using a 7805 type regulator or equivalent (like an LM2931) and power the entire circuit using a 9V battery sitting in the bottom of the Radio Shack project box. The circuit only calls out +5V supply lines. How you get there is up to you.

Also, the schematic does NOT show an On/Off power switch. I included one in the Bill of Materials. Just put it in the +5V line going to the Vdd pin. If you use this, you don't need a separate Reset Switch (SW5), but you could leave one in for convenience.

Another thing to note is that the 16F84 datasheet recommends using a 50-100 ohm resistor in series with the MCLR when it's pulled to ground. I haven't had any problems with pulling it directly to ground, but it's probably better to be safe. Just connect a 100 ohm resistor between the switch SW5 and ground.

As far as the code is concerned, particularly note the asynchronous speaker oscillation and input button polling. There are some examples of fine code (as well as some not-so-great code) in the program. Also, EEPROM data recall code is pretty solid, and use of the FSR register is nice. If you are a beginner, you might learn something from this program. If you're an expert, write your own code if you don't like it!




Bill of Materials (with Digi-Key part number and quantity):
PIC16F84	PIC16F84			PIC16F84-04/P-ND	1
SW6		on/off and difficulty switch	SW101-ND		2
SW1-4		momentary buttons		SW421-ND		4
SW5		momentary reset button		SW401-ND		1
L1		Piezo Buzzer			P9924-ND		1
D1		Red LED				160-1045-ND		1
D2		Green LED			160-1049-ND		1
D3		Yellow LED			160-1053-ND		1
D4		Orange LED			160-1109-ND		1
(Note: These above LEDs have resistors ALREADY INSIDE the LED housing.)
(If you want to use another type of LED, you'll have to use the 220-820 ohm)
(resistor network shown on the schematic.  If you use the above specified)
(LEDs, you do not need the resistor network, just connect them directly to)
(ground.  Also, I indicated a Blue LED on the schematic and in the ASM code)
(but the orange one is brighter and is available with the integral resistor.)
18pF Capacitor			BC1004CT-ND		1
4.7K resistor			4.7KEBK-ND		1
10K resistors			10KEBK-ND		2
10K resistor network		4606X-1-103-ND		1
Total parts cost: less than $10.00, not including PIC or project box


See also:



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