Fullscreen HTML5Med Res (??MB)HTML4

Max’s Cool Beans By Max the Magnificent Weird & Wonderful Arduino Projects Part 14: enough playing games, it's time to play games! H ello there. But that's enough of the pleasantries. Hold on to your hat because I have exciting news. Believe it or not, we are finally ready to take all the disparate elements we’ve worked on in previous columns and bring them together to form our retro games console. As a reminder, in addition to our Arduino Uno, we have the 14 × 10 array of tri-colour light-emitting diodes (LEDs) that we created in Part 3 (March 2025). We also have our six 7-segment displays (implemented as three two-digit prebuilt modules) that we already mounted on the front panel in Part 13 (January 2026). Last, but not least, we have our switches, which we’ve already attached to the front panel, but have not yet wired up. As a further reminder, in these discussions I’m assuming that (like me) you will be using a laser-cut front panel and a 3D-printed enclosure. As previously noted, you could simply attach everything to a timber board using hot glue. If anyone asks, you can tell them it’s a prototype and then fix them with a steely glare (my dear old mother could give lessons in the art of the steely glare). A rush of power When running in standalone mode (not connected to a host computer via a USB cable), the Arduino Uno requires a 9V supply. This can be presented using its power jack or via its VIN pin. The Arduino will use its onboard voltage regulator to drop the 9V supply to the 5V it requires for its internal operations. Way back in the mists of time (April 2025), we decided to power our console using an external 9V supply. In my case, I’m using a very tasty NAN4 KADF (gesundheit) 30V 10A bench power supply. On the off chance you are in the market for one of these little beauties, the same unit is available on Amazon UK (https://pemag.au/ link/ac48). Our 14 × 10 LED array and our 7-segment display modules both require 5V to power them. To address this, we decided, in the April 2025 issue, to use a cheap-and-cheerful DCto-DC converter module (see Photo 1). These devices, available from Amazon UK (https://pemag.au/link/ ac2m), accept input voltages from 9V to 24V and claim to deliver up to 5A at 5V. In reality, the ones we tested struggled to deliver more than 2A. Happily, we require only around 1.5A for our games console, well within its capabilities. A high-level view of our proposed power supply setup is shown in Fig.1. Bits and pieces Before we leap into action, let’s take a moment to remind ourselves where all the bits and pieces go (Fig.2). When you look at the front of the console, as illustrated in Fig.2(a), you may note that I’ve transposed the Action and Direction control buttons compared to our original prototype. This wasn’t intentional. It was only after I’d attached the 7-segment display modules th at I r ealised I’d mounted them on the wrong side of the panel. I could have fixed this, but then I thought, “What the heck!”. When we look at the back of the console, shown in Fig.2(b), we see that I decided to mount the DC-toDC converter on the back of the 14 × 10 LED array panel (I used trusty hot glue for this purpose). Tips and tricks (and other stuff) Don’t forget that when you’re working with semiconductor devices, including LEDs (like our 7-segment display modules and our 14 × 10 array), you should always use an antistatic mat and an antistatic wrist band. Of course, these need to be properly grounded. We discussed this in our first Arduino Bootcamp column (January 2023). I’m assuming that you know how to solder. If not, may I be so bold as to recommend The Basic Soldering Guide Handbook (pemag.au/link/ ac9o), written by my friend and fellow PE contributor Alan Winstanley. Photo 1: this DC-toDC converter module can efficiently produce a regulated 5V output from a 9-24V input. Practical Electronics | February | 2026 9V VIN+ 0V (GND) VIN- 5V DC-DC Converter 14x10 LED Array 0V MCU (Arduino) 7-Segment Displays Fig.1: our power supply configuration. Whenever possible, use heatshrink tubing to protect your soldered joints. For example, in a moment, we’ll be soldering wires to a 25-way D-sub connector, and you should apply heatshrink tubing to each connection. This serves two purposes: it prevents unwanted short circuits, and it provides strain relief for the connections when the wires flex as you work with them. When I first embarked on this project, I imagined a solid enclosure with a removable front panel. The more I thought about it, however, the more I realised what a pain that was going to be. As you’ll see in the photos of the finished unit later in this column, I eventually decided to permanently mount the front panel to the front of the enclosure, leaving the rear open, with just a band of material around the back edge. My plan is to add a proper back panel later, but for now, this open rear gives me full access to wire everything from the back. Delightfully different Back in the 1980s and 1990s, most home game consoles were built around the concept of plug-in game cartridges. This was long before the age of the internet, digital distribution or downloadable content. If you wanted a new game, you bought a physical cartridge, slid it into the slot, and— assuming you’d chanted the correct incantations—off you went. In those days of yore, commercial game cartridges didn’t include processors. The main processor was built into the console itself. The cartridges were essentially clever little boxes of read-only memory (ROM) that held the game code and data. When you inserted a game, the console’s processor executed the code directly from the cartridge’s ROM. Having said that, some cartridges did get a bit fancy. To work around the limitations of the host console, manufacturers occasionally added extra hardware into the cartridges, such as bank-switching ‘mapper’ chips, additional RAM, custom audio chips, or even the occasional co-processor (the most famous being the Super FX chip used in Star Fox for the Super Nintendo). Even so, the core idea remained the same: the console provided the brainpower, while the cartridge provided the instructions. We dare to be different. In our case, each plug-in game cartridge will contain its own Arduino microcontroller with the game code stored in its flash memory, thereby making it an independent computing node. In this case, the console itself becomes more of a shared backplane that supplies power, buttons, and displays. The cartridge plugs in, commandeers the hardware, and away we go. The bottom line is that, although 25-way D-sub connector (game cartridges plug in here) 7-Segment Displays Power Jack From external supply VIN- (0V) Reset Button VIN+ (9V) 14 x 10 Tricolor LED Array 9V 0V DC-to-DC converter 0V 5V To array and displays R Y Action Controls N W G B E Direction Controls N (a) Front view 15-way D-sub connector (additional controls can plug in here) (b) Back view Fig.2: the main elements of the retro games console. Practical Electronics | February | 2026 5 9V 0V N S RCLK W SER E Vin 0V 5V D3 D5 D7 D9 D11 D13 1 3 2 4 5 6 7 8 9 Inside the case A1 A3 A5 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 24 0V 0V D2 D4 D6 D8 D10 D12 RES A0 R Y G A2 A4 SRCLK B To/from Arduino outside the case Inside the case NEOS RESET Fig.3: the connections that need to be made on the 25-way connector. our design isn’t a faithful recreation of how retro game cartridges worked internally, it does capture the spirit of slotting in a physical game module and instantly transforming the experience. And, honestly, that’s half the fun. Feeling connected Let’s start with the 25-way D-sub connector mounted at the top of the enclosure (Fig.2). If we imagine ourselves peering at it from the inside of the enclosure, the pinout we’d see is shown in Fig.3. In this first pass, I’m only going to wire (and use) the connections shown in black. I’ll add Photo 2: just call me a soldering fool. 6 the connections shown in red at a later date. The 9V and 0V (GND) power supply signals inside the enclosure will be wired to pins 1 and 2 on the connector, respectively. In turn, these supplies will be fed to the Arduino’s VIN and 0V (GND) pins on the game cartridge. The north (N), south (S), east (E) and west (W) direction control switches inside the enclosure will be wired to connector pins 4, 5, 6, and 7, respectively. In turn, these signals will be fed to the Arduino’s digital D3, D5, D7 and D9 pins on the game cartridge. The red (R), yellow (Y), green (G) and blue (B) action control switches inside the enclosure will be wired to connector pins 16, 17, 18, and 19, respectively. In turn, these signals will be fed to the Arduino’s digital D2, D4, D6 and D8 pins on the game cartridge. The black reset button on the side of the enclosure will be wired to pin 22 on the connector. This signal will be fed to the Arduino’s RESET input on the game cartridge. Meanwhile, the Arduino will con- trol the 14 × 10 array of tri-colour LEDs (aka Neopixels) using its digital pin D10, which will be fed from the cartridge to pin 20 on the connector. In turn, we will wire this pin to the input of our array. Similarly, the Arduino will control the 7-segment display modules using its digital pins D11, D12, and D13, which will be fed from the cartridge to pins 8, 21, and 9 on the connector. In turn, we will wire these pins to the SER (serial data in), SRCLK (shift register clock), and RCLK (output register clock) pins on our display modules, respectively. I messed up here because I started by jotting down my connection plans on a piece of paper, which eventually became Fig.3. I then wired things up as per my jottings (Photo 2). It was only after I’d finished that I realised I’d transposed the SRCLK and RCLK signals on my original diagram. That is, in our earlier programs, we used to drive each of these signals with the other’s pin (if you see what I mean). Fortunately, the solution to this was easy-peasy lemon squeezy; all I had to do was swap these pins in my code, but we will return to that later. For future reference For this initial trial, I didn’t bother wiring up the 15-way D-sub connector mounted at the bottom of the enclosure. As you may recall, this is intended to allow additional controls and sensors mounted on a mini console to be plugged in at some point in the future. You can, of course, wire your system up as you wish. For the sake of interest, the way I’m currently planning to wire my 15-way connector is illustrated in Fig.4. Once again, I’m imagining that we are peering at this connector from inside the enclosure. The way I’m envisaging things, we Outside 5V 0V N S E W would feed 5V and 0V the case (GND) from the main console to power any5V 0V A1 A5 D3 D5 D7 D9 thing that needs powering on the mini console. We could have a Inside 1 2 3 4 5 6 7 8 second set of action the case 9 10 11 12 13 14 15 and direction buttons mounted on the mini console, perA0 A2 A4 D2 D4 D6 D8 haps for use in twoplayer games. Alternatively, we could Outside R Y G B mount two four-way the case momentary-­c ontact joystick switches on Fig.4: the connections to the 15-way connector. Practical Electronics | February | 2026 0V RESET 22, RES 5 0V N 4, D3 6 0V 0V 0V 0V S E W R 5, D5 7 6, D7 8 7, D9 12 16, D2 13 0V 0V Y G 17, D4 14 18, D6 15 0V B 19, D8 25-Way 15-Way Fig.5: the console switch wiring. the mini console. In both these cases, the signals from these switches/joysticks would be wired in parallel to the switches inside the main console. Instead of using 4-way momentary-­ contact joystick switches, we could add two two-axis analog joysticks to the mini console. Each of these joysticks would have two analog outputs. We could feed these to the A0, A1, A2 and A4 pins on the connector. Inside the main console, these pins would be wired to the corresponding A0, A1, A2, and A4 pins on the 25-way connector, which would then feed them into the processor on the game cartridge. Did anything catch your eye in Fig.4 and in the preceding paragraph? You’re right; there’s no A3 pin. That’s because I ran out of pins on the connector. We could move to using a bigger connector, but I’m happy with the 15-way one we currently have. So, why do I show A0, A1, A2, A4, and A5 in Fig.4 (as opposed to A0, A1, A2, A3, and A4)? The reason is that on the Arduino Uno R3 (which we are using), the primary I2C pins are A4 (the data line, SDA) and A5 (the clock line, SCL). Maintaining access to these lines means we have the ability to deploy all sorts of I2C sensors (such as a threePractical Electronics | February | 2026 Photo 3: wiring is fun… axis accelerometer and/or a three­axis gyroscope) via our mini-console. As one final point, just as we can create multiple plug-in game cartridges, we can also create multiple plug-in mini consoles. The world truly is our lobster (or crustacean of your choice). The old switcheroo Last, but certainly not least, we have to wire our switches to the 25-way connector (and the 15-connector, at some stage), as illustrated in Fig.5. Switches are usually reliable. It’s relatively rare in the scheme of things that you end up with a duff switch. On the other hand, it can happen, so …but not as fun as finishing! it’s a good idea to use the continuity tester on your multimeter to verify that your switches work before you attach them to the console (or, at least, before you start soldering wires to them). This takes only a minute, and it can save much hair-pulling later. The result of my wiring frenzy is shown in Photo 3. A plan of action Once all the wiring was completed, the next thing I did was to create a plan of action (“If we don’t have a plan, we’re no better than the French”, as the old saying goes). [No doubt there’s a French saying that translates as “If we don’t have a plan, we’re 7 no better than the English” – Editor] There are three main aspects of the console that we need to test before proceeding further: • The 7-segment displays • The 14 × 10 array • The switches I decided to start with the low hanging fruit in the form of the 7-segment displays. I took the final program from our previous column (January 2026)— the one that displayed a level from 1 to 9 coupled with a score counting up from 0000 to 9999—and I tweaked the pins to match my wiring ‘gotcha’ as discussed earlier in this column. This means we now have the SER, SRCLK and RCLK signals connected to Arduino pins 11, 12, and 13, respectively. I uploaded this new program into the Arduino before I connected it to the console, just to be sure I had a clue what it would do when I powered everything up. I’ve made a copy of this updated version of the code available in the file named CB-feb26code-01.txt (as usual, all files mentioned in this column are available as part of the February 2026 download package from the PE website at https://pemag.au/link/ac9p). A roll of drums In our next column, we will create our Arduino-Uno-based game cartridge. In the meantime, I just happened to have a DB25 male-to-barewire connector in my treasure chest of parts (Photo 4). These are available on Amazon (https://pemag.au/link/ac9q). The great thing is that all the wires are different colours, and each end has a little band with the pin number printed on it. They are quite expensive, so I wouldn’t suggest buying one just for this project. On the other hand, if you happen to have one lying around… I chopped the existing pins off the ends of the wires (they were too big to plug into my Arduino’s headers), used my crimping tool to attach appropriate pins, and then plugged them into my Arduino. Next, I plugged the other end of the cable into my console. Remember that the Arduino will now be powered from the console, but we’ll still need to use the USB cable to upload future programs into it. This is the point in a project when one’s heart is in one’s mouth. When you apply power, will everything work as planned (hey, it could happen!), will your creation simply sit there sadly, or will it add a little excitement to your life by bursting into flames? When you’ve been at this game as long as I have, you’ll have sampled 8 Photo 4: a handy-dandy DB25 male-to-bare-wire connector. the delights of all three scenarios. The first thing I did was power up my bench power supply and set the voltage to 9V and the current to 2A. I connected the supply to the console, then I pressed the “Output” button. I was poised to power down if I heard or smelled anything untoward and… nothing happened. “Oh, bother”, I said (or words to that effect). I looked at the displays on the bench power supply. The voltage showed 9V, but the current showed 0A. Then I looked lower and realised that the positive wire had somehow become disconnected from the supply. Phew! So I powered it down, reconnected the errant wire, and repeated the power-up process. It worked! The count commenced as expected. I was wearing my happy face. I pressed the reset button on the console. That worked too. I felt a roll of drums was in order, but there’s never a drummer around when you need one, so I had to make do with an imaginary drum roll in my head (my ears are still ringing). Testing the main 14 × 10 array The next step was only a little more complicated. First, I took the latest and greatest program we created to drive our 14 × 10 array, from the May 2025 issue. This is the one that repeatedly draws randomly sized rectangles at random locations on the display. Furthermore, each rectangle has a random outline colour and a (different) random fill colour. I changed the pin number driving the Neopixel string to 10 to match the wiring in the console. I also copied just enough of the 7-segment display test code to clear the 7-segment displays and set their control pins to their inactive states. If I hadn’t done this, the control pins would have been left in high-impedance states, which would have resulted in the 7-segment Practical Electronics | February | 2026 If all 0s WFZ Note: All switches are active-low JGA If not all 0s Names of states If not all 1s WFZ = WAITING_FOR_ZEROS JGA = JUST_GONE_ACTIVE WFO = WAITING_FOR_ONES JGI = JUST_GONE_INACTIVE WFO Names of functions JGI UpdateSwitches() ProcessSwitches() If all 1s Fig.6: our new switch debounce state machine displays flickering annoyingly with random values. Oh Joy! This program also worked the first time. I was on a roll. I’ve made a copy of this code available in the file named CB-feb26-code-02.txt. Testing the switches My final test involved the switches. When we last looked at debouncing switches (August 2025), we were working with three breadboard-mounted momentary pushbuttons with a mix of active-high and active-low states. Since all the switches on our console are active low, I decided to update the state machine we are using. The new version is depicted in Fig.6. Next, I took a copy of our latest switch debounce code (August 2025) and modified it to handle our eight switches using our new state machine. VERY IMPORTANT: I don’t know if you noticed in Fig.5 that we aren’t using any pull-up resistors with our switches. In this case, we declare these pins as INPUT_PULLUP in our code, which activates the Arduino’s internal pull-up resistors (yes, of course we could have done this before, but where would the fun be in that?). Once again, I copied just enough of the 7-segment display test code to clear the 7-segment displays and set their control pins to their inactive states. Also, I copied just enough of the 14 × 10 array code to ensure that the array was initialised and deactivated. I’ve made a copy of this code available in the file named CB-feb26code-03.txt. As you may recall, in our switch handling code, we first call our UpdateSwitches() function, which cycles through all the switches, reads their states, and updates their state machines. Then we call our ProcessSwitches() function, which deals with any game-specific actions. For example, the game-specific code associated with the north (N) switch in our current test program is shown in Listing 3(a). Remember, we’re using the convention that the listing number (3 in this case) corresponds to the numerical part of the matching code file name (“03” here). The way we’ve architected this means we can use the same code across all our future game programs. All we will need to do is modify the ‘Optional (game-­specific)’ part of the code. For the moment, all we are doing is pressing the switches and ensuring that the appropriate messages appear in the serial monitor window. In my case, I’m seeing: 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 : Switch North just went active Switch North just went inactive Switch South just went active Switch South just went inactive Switch East just went active Switch East just went inactive Switch West just went active Switch West just went inactive : This is where we ensure the switches are wired to the correct pins on the connector. If we’ve made any mistakes, we can easily rectify them by tweaking the pin definitions in our code. Next time We’ve made great progress in getting the games console working this month! Our next column will be the final one in this project (although we will still add new games and things in the future). We will start by building our first game cartridge and creating our first game. In the meantime, you could create a test program of your own. How about a simple Etch-A-Sketch program? You could start by flashing a cell in the middle of the array with one of our four action button colours (red, yellow, green, or blue). Pressing one of the north, south, east, or west direction buttons could lock this colour into this cell and advance the cursor (the active flashing cell) in the specified direction. Pressing one of the action buttons could change the selected colour. If you have any thoughts on anything you’ve read here, please feel free to email PE me at max<at>clivemaxfield.com // Switch North if (Switches[SW_NORTH].swState == JUST_GONE_ACTIVE) { // Mandatory Switches[SW_NORTH].swState = WAITING_FOR_ONES; // Optional (game-specific) Serial.println("Switch North just went active"); } else if (Switches[SW_NORTH].swState == JUST_GONE_INACTIVE) { // Mandatory Switches[SW_NORTH].swState = WAITING_FOR_ZEROS; // Optional (game-specific) Serial.println("Switch North just went inactive"); } Listing 3(a): a portion of our new switch handling routine. Devices and components used in this issue Arduino Uno R3 microcontroller module Dual 7-segment display modules PCB spacer kit (black, M3) Pushbuttons (assorted colours) 2.1mm panel-mount DC power socket 2.1mm standard DC power plug 25-way D-Sub panel-mount socket 15-way D-Sub panel-mount socket 22 AWG multicore wire kit Practical Electronics | February | 2026 https://pemag.au/link/ac2g https://pemag.au/link/ac8i https://pemag.au/link/ac4u https://pemag.au/link/ac2t https://pemag.au/link/ac2v https://pemag.au/link/ac2w https://pemag.au/link/ac2x https://pemag.au/link/ac2z https://pemag.au/link/ac3m 9