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Simon Says . . . Ahhhh! – nostalgia, it ain’t what it used to be. We take a look at how electronic games have changed over the last 25 years and describe a new “Simon Says” game for you to build. By CLIVE SEAGER R EMEMBER THE 70s? The BBC in the UK recently produced a series of television programs called “I Love 197x”. You certainly start to realise your age when you discover that 1978 was over 25 years ago! The 1978 program made reference to the cult toy of the year, “Simon”, made by MB Games, which was loved by children Fig.1: this page from the General Instruments 1977 catalog lists the PIC1650 as a “Programmable Intelligent Computer” 76  Silicon Chip and loathed by parents! This was one of the very first mass-produced electronic games and I remember playing it with friends and relatives. Simon For those too young to remember 1978, the idea behind the Simon game was quite simple. It was based on the old school playground game “Simon Says”. The game was made up of a big round plastic case with four coloured panels. Each panel concealed a switch and a light bulb. At the start of a game, the electronics inside would light up one of the four panels briefly and sound a tone. The player then had to press that panel, after which Simon would repeat, lighting the same panel briefly and adding another. Again, it was the player’s turn. He or she then had to press the two panels in the correct sequence. Each round, the number of panels increased by one until the player could no longer remember the correct sequence. Simon would then issue a harsh buzz and end the game. As I watched the TV program, it struck me that this vintage toy from 1978 could probably be reproduced with a PICAXE microcontroller at very low cost. So I set myself the task of building This is the original MB “Simon” game from 1978. my own PICAXE version of the “Simon Says” game, particularly as I thought it would provide a perfect example of how to remember sequences in a PICAXE BASIC program, something that many users find quite difficult. Internet trivia A quick Google search on the Internet soon revealed lots of trivia about the original “Simon” game. The first single-player game was released in 1978. Subsequently, MB released “Super Simon” in 1979, which had two sets of panels for two players. In 1980, a smaller version called “Pocket Simon” appeared. There was also a special edition Simon with a clear casing so that the internal workings could be seen. Apparently, “Super Simon” even makes an appearance in the film “ET”, where it can be seen on the shelf behind ET’s head when he first speaks! However, I was more interested in how the original game worked. I discovered it needed both a 9V PP3 and two large D cells to make it work, presumably to power the light bulbs and speaker, but could not discover much more online. Then using my “you can buy anything on eBay” philosophy, I did a quick search and sure enough, dissiliconchip.com.au covered that I could buy a real Super Simon, complete with box and instructions, for just £5. So five days later I was the proud owner of a vintage game, which I then, as you probably expect by now, completely disassembled! The original game Removing the cover exposed a sparsely populated PC board. It consisted only of a metal switch contact, eight bulbs buffered by a couple of standard logic gates, and a Texas Instrument “microcomputer” chip. These microcomputer chips were some of the first “single-chip” controllers widely used in mass-produced consumer products, and can be found in a wide range of early 80s equipment such as vending machines. They were the predecessors of the modern PIC microcontrollers. Many people think microcontrollers are a relatively new idea, when in actual fact this game was using very similar single-chip technology 25 years ago! What does “PIC” stand for? One of the most common questions we are asked is “what do PIC and PICAXE actually stand for?” Back in 1975, General Instruments Microelectronics Division developed a small 8-bit controller (PIC1650) based on the Harvard architecture, which itself had been created as part of an earlier inter-university Defence Department competition. Many sources quote the PIC1650 controller as being created primarily as a support input/ output device for the more powerful CP1600 16-bit processor and so quote PIC as standing for “Peripheral Interface Controller”. However, a rare scanned copy of the 1977 General Instruments “Micro-electronics” catalog tells a different story. Fig.1 shows the PIC1650 page from this catalog, which lists the device as a “Programmable Intelligent Computer”. The datasheet clearly shows that this device was the “first in breed” of all the later PICmicro devices, even though is was only available in masked ROM version using NMOS technology. In the early 80s, a venture capital group purchased 85% of the GI Microelectronics Division, including the Arizona manufacturing plant, and formed the Microchip company as it is known today. This new company combined the original PIC1650 techsiliconchip.com.au “Super Simon” came a year after the original “Simon” game and featured twoplayer support. A disassembled “Super Simon”, revealing the TI microcontroller (the larger 28pin chip) and not much more. nology with EPROM memory to create the one-time-programmable PICmicro “C” series parts known today. Later they added erasable EEPROM memory to create the PIC16C84, then the 16F84, and subsequently all of the “F” (FLASH) series parts. Therefore, PIC can stand for either January 2005  77 Fig.2: the circuit diagram for “Simon Says” is a PICAXE incarnation of the game. As with the original, a single-chip micro handles all the smarts but LEDs and a piezo sounder replace the incandescent bulbs and speaker. “Peripheral Interface Controller” or “Programmable Intelligent Computer” – take your pic(k)! PICAXE is easier to explain; it is simply a brand name based on a play of words! The new Simon game The circuit diagram for the PICAXE version of the game is shown in Fig.2. As you can see, it’s very straightforward indeed, consisting of just the micro, four LEDs, a piezo sounder, five pushbutton switches and a few resistors. PC board assembly is also quite straightforward. Use the overlay diagram in Fig.3 as a guide to component placement. Take care with the orientation of the four LEDs, which must have their flat (cathode) sides positioned as shown. Also, make sure the notched (pin 1) end of the PICAXE micro faces the serial link socket. Before soldering (1). Wait for the player to press a switch to start the game. (2). Generate a sequence of random numbers, ranging from 0-3 for the four LEDs. In this case, I will use 100 steps; many more than the seven or eight I can normally repeat in a game! These numbers are stored using the write command in the PICAXE-18A’s separate data memory, which actually has space for up to 256 steps. (3). Get the microcontroller to play back the numbers. To do this, the micro must know how many steps to play back in each round of the game. A variable called topstep will be used to remember the number of steps. If topstep = 1, one step will be played back, if topstep = 2, two steps will be played back, and so on. (4). When the player presses a switch, the microcontroller must light the correct LED for that switch and then compare the switch press to see if it is in sequence. The micro must therefore count the number of switches the the battery clip leads, thread them through the adjacent hole to provide strain relief. Power your completed project only from a 3 x AA alkaline cell (4.5V) battery pack or regulated 5V DC supply. Take particular care that you have the power leads around the right way, otherwise you’ll destroy the PICAXE! Programming introduction The programming task for the Simon game is fairly complicated but is a good example of how to “remember” sequences using the separate data memory (available in all the “A” and “X” series PICAXE micros). When approaching a complicated problem like this, it is essential to break the overall task down into small, manageable chunks and then put the whole program together at the end. The following tasks were identified: Table 1: Resistor Colour Codes o o o o o No.    2   1   1   4 78  Silicon Chip Value 10kΩ 22kΩ 4.7kΩ 330Ω 4-Band Code (1%) brown black orange brown red red orange brown yellow violet red brown orange orange brown brown 5-Band Code (1%) brown black black red brown red red black red brown yellow violet black brown brown orange orange black black brown siliconchip.com.au Parts List 1 Simon PC board 1 3.5mm stereo socket 1 miniature pushbutton switch (SW5) 4 pushbutton switches (SW1 – SW4) 1 battery clip 1 3 x AA battery holder 1 18-pin IC socket 1 miniature piezo transducer Semiconductors 1 PICAXE-18A microcontroller 1 5mm green LED 1 5mm red LED 1 5mm yellow LED 1 5mm blue LED Fig.3: follow this diagram when assembling the board. Take particular care with the orientation of all the LEDs, the PICAXE micro and the power input leads. Capacitors 1 100nF (0.1µF) MKT (code 100n or 104) Resistors (0.25W 5%) 2 10kΩ 1 4.7kΩ 1 22kΩ 4 330Ω 1 10kΩ trimpot (VR1) Also required (not in kit) PICAXE Programming Editor software (v4.1.0 or later) PICAXE download cable (part AXE026) 3 AA alkaline cells Obtaining kits and software This is what the completed PC board looks like. Power comes from an external 4.5V battery pack consisting of three AA alkaline cells. player has pressed. These are accumulated in the playerstep variable. (5). When the player reaches the end of the sequence, the microcontroller must acknowledge the success, add one to the value of topstep and then repeat the process from (3) above. If the player gets the sequence wrong, a buzzer will sound and the game will reset. Program The full program listing is shown siliconchip.com.au in the accompanying panel. Although the program is quite complex, we’ve included it here as an example of what can be achieved with PICAXE microcontrollers. Full comments are given in the program but a brief explanation is also included below. Note: to save typing the program in manually, you can download it from the SILICON CHIP web site at www.siliconchip.com.au. Section 1 in the program is a loop that lights all four LEDs, generates a The design copyright for this project is owned by Revolution Education Ltd. Complete kits (part AXE106K) for this project are available from authorised PICAXE distributors – see www.microzed. com.au or phone Microzed on (02) 6772 2777. The PICAXE Programming editor software can be downloaded free of charge from www.picaxe.co.uk or ordered on CD (part BAS805). random number and then waits for a switch to be pressed to start the game. By including the random command within the loop, it is constantly varying and so no two games will be the same. Section 2 uses a for…next loop to store 100 random numbers in the micro’s memory. As the PICAXE random command only works on word variables, it is called using the variable randword. However, as we only January 2005  79 Simon Says PICAXE BASIC Program ' *** Define the variables used *** symbol randword = w0 'random number (word) symbol randbyte = b0 'random number (byte, part of w0) symbol value = b2 'switch value 0-1-2-3 symbol playerstep = b3 'position of player in game symbol freq = b4 'sound variable symbol topstep = b5 'number of steps in sequence symbol counter = b6 'general purpose counter symbol speed = b7 'playback speed ' *** Section 1 ********************** ' Wait for any switch to be pushed init: let pins = %00001111 random randword if input0 = 1 then preload if input1 = 1 then preload if input6 = 1 then preload if input7 = 1 then preload goto init 'light all LEDs 'randomise 'check switches ' *** Section 2 **************************** ' Load EEPROM data memory with 100 numbers preload: let pins = %00000000 for counter = 0 to 100 'LEDs off 'for..next loop let value = 0 random randword 'get random number if randbyte > 180 then set0 if randbyte > 120 then set1 if randbyte > 60 then set2 set3: let value = value + 1 set2: let value = value + 1 set1: let value = value + 1 set0: write counter,value next counter '1+1+1 = 3 '1+1 = 2 '1 '0 'save in data memory 'next loop ' *** Section 3 **************************** ' This section plays back a sequence let pins = %00000000 let topstep = 1 playback: readadc 2,speed for counter = 1 to topstep read counter,value gosub beep pause 300 next counter 'LEDs off 'reset step number to 1 'read speed value from preset 'for...next loop 'get value 'make the noise 'short delay 'loop ' *** Section 4 ************************************** ' Now the user responds playerstep = 1 ' If playerstep is greater than topstep then all done 80  Silicon Chip gameloop: if playerstep > topstep then success read playerstep,value 'recall correct value loop: if input7 = 1 then pushed0 'wait for switch press if input0 = 1 then pushed1 if input1 = 1 then pushed2 if input6 = 1 then pushed3 goto loop ' Now check correct value depending on which switch was pressed pushed0: if value <> 0 then fail let playerstep = playerstep + 1 gosub beep goto gameloop pushed1: if value <> 1 then fail let playerstep = playerstep + 1 gosub beep goto gameloop pushed2: if value <> 2 then fail let playerstep = playerstep + 1 gosub beep goto gameloop pushed3: if value <> 3 then fail let playerstep = playerstep + 1 gosub beep goto gameloop ' Failed so make noise and jump back to start fail: let pins = %0000000 'all LEDs off sound 7,(80,100) 'make a noise sound 7,(50,100) goto init 'back to start ' Succeeded so add another step to sequence and loop success: pause 100 'short delay let pins = %00001111 'all LEDs on sound 7,(120,50) 'success beep let pins = %00000000 'all LEDs off pause 100 'short delay let topstep = topstep + 1 'add another step goto playback 'loop again ' *** Section 5 **************** 'Sub-procedure to light correct LED and make beep beep: high value freq = value + 1 * 25 sound 7,(freq,speed) low value return 'switch on LED ‘generate sound freq. 'play sound 'switch off LED 'return siliconchip.com.au require a byte value, we later use the variable randbyte (one half of randword). We only require the numbers 0-3 (for the four LEDs) but randbyte can contain the value 0-255 and so we carry out a simple comparison test to get the four desired values. Section 3 switches all four LEDs off and then uses a for..next loop to play back the sequence (up to the variable topstep). The “beep” sub-procedure in section 5 is used to light the appropriate LED and make a sound for each step. Note that the sound is different for each LED to aid memory during the game. The length of the beep is determined by the setting of trimpot VR1, which can therefore be used to increase or decrease the speed of the game. Section 4 first resets the player’s position to 1. A test is then carried out to see if the player has completed all the required steps. If all steps have been done, the “success” section of the code flashes all four LEDs, adds one more step to the topstep value and then loops back to section 3. If there are still steps to do, the correct target value is retrieved from memory for comparison. The program then enters a loop, waiting for a switch to be pressed. When a switch is pressed it is compared to the target value retrieved from memory. If the values are the same, everything is correct and so the LED is lit via the “beep” sub-procedure, the players position is increased by one and the program loops back for another switch press. If the value is incorrect, the “fail” section of the code makes a noise and then resets the game. Summary Single-chip controllers are not new, as this game was using them 25 years ago! However, electronics has changed dramatically since then and modern microcontrollers are much cheaper and easier to use than the original micros. Modern microcontrollers such as the PICAXE reduce large complex circuits down to simple, clean designs and dramatically reduce the cost of these products. LED technology has improved and no game would ever be manufactured now with bulbs due to cost, safety and power consumption. Microcontrollers are here to stay! SC Want cheap, really bright LEDs? We have the best value, brightest LEDs available in Australia! Check these out: Luxeon 1, 3 and 5 watt All colours available, with or without attached optics, as low as $10 each Low-cost 1 watt Like the Luxeons, but much lower cost. •Red, amber, green, blue and white: Just $6 each! Lumileds Superflux These are 7.6mm square and can be driven at up to 50mA continuously. •Red and amber: $2 each •Blue, green and cyan: $3 each Asian Superflux Same as above, but much lower cost. •Red and amber: Just 50 cents each! •Blue, green, aqua and white: $1 each. Go to www.ata.org.au or call us on (03)9419 2440. 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