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Colour Maximite Computer Part 4 Words: Phil Boyce Design: Geoff Graham A retro 80s home computer with modern-day features Graphics capabilities, demo programs and hardware control I n Part 3, we covered the three Maximite modes: Immediate, Editor, and Run (and how to switch between them) allowing you to test commands, enter code, or run a program. We also showed how to save and load a program from the SD card – this included running the game Donut Dilemma, which demonstrated just how versatile MMBASIC really is. In this final part of the project we will work through a number of other demo programs; some will show the graphics capabilities of the Colour Maximite Computer, and others will challenge you, with some fun thrown in! We will finish by explaining how to access the GPIO pins to control external hardware, with a quick practical project: the Maximite Mood Light. The topics covered this month are deliberately kept at a high level because we want you to explore your Colour Maximite Computer. Do download the User Manual (http://geoffg.net/maximite. html) – it contains extra detail and useful examples of hardware interfacing. This month’s download There are many programs that we will be referencing and using in this final part of the Colour Maximite Computer project, so this month’s download contains more files than usual. Start by downloading the CMC_DemoPrograms folder from the February 2020 page of the PE website. Unzip the folder, and then copy the contents (comprising multiple files and directories) directly 42 onto your SD card. Next, power up your Maximite, insert your SD card, and you will see the usual flashing cursor (command prompt) meaning that the Maximite is in Immediate mode and waiting for a command to be entered. To check that your SD card has been prepared correctly, type FILES (Enter) and you should see a list of folders (shown as a list of <DIR> folder_name) followed by a list of files (.bas, .fnt, .spr, .mod, .txt) listed alphabetically. If you don’t see this, then make sure you correct things before proceeding. At various points throughout this article, we will reference a specific program (by filename) that you need to run. Before you run the program you will first need to locate the appropriate .bas file (the .bas extension means program code). There are two possible scenarios: 1. It is in the initial FILES list when you first power up the Colour Maximite Computer – think of this as the ‘root folder’ 2. It is in a dedicated folder (<DIR>) which has a folder name similar to the filename (more on this shortly). Taking these two scenarios in turn: 1. Some programs will comprise just a .bas file. These are typically found in the root folder – try it now by typing FILES (Enter) and check that you can see MODES.BAS 2. Several of the demo programs require extra support files such as sprites (.spr), bitmaps (.bmp), fonts (.fnt), and/or sounds (.mod) – this is in addition to the .bas file. To keep things tidy, these multi-file programs have all of the required files inside their own dedicated folder (shown as <DIR> folder_name when you type FILES in the root folder). So in order to locate the .bas file for a multi-file program, you will first need to switch to the relevant folder with the change-directory command, CHDIR folder_name (as we did last month when running the Donut Dilemma game from the DONUT folder). Typing FILES (Enter) shows you all the files that make up the multi-file program. To return back to the root folder, type CHDIR .. (Enter). In effect, this goes up a folder level. An alternative is to simply reset the Maximite (power off, then back on) – by default, the root folder is always accessed first. Once you have located the relevant .bas file, you could run the program by typing (at the command prompt) LOAD "filename.bas" (Enter), and then RUN (Enter). However, MMBASIC lets you shorten this by typing RUN filename (Enter). Note that the double quotes around the filename can be omitted, as well as the .bas file extension. Please note that some programs will use screen MODE 4 (240 × 216 pixels) and/or different-sized font characters. This can mean that when you stop the program and return to the command prompt (Ctrl-C), the characters that appear on the screen will be much bigger than normal. Typing MODE 3 Practical Electronics | February | 2020 (Enter) will generally return the characters to normal size – alternatively, reset the Maximite by temporarily removing power (or by typing WATCHDOG 1 to reset the processor). All this may seem a bit confusing at first, but all we’re doing here is keeping things tidy on the SD card. After running the first few programs from this month’s article, things will become very straightforward – I promise! Graphics capabilities We’ve already explored some of the easier graphics commands in the User Manual, but do have a play with the commands CLS, PIXEL, LINE, and CIRCLE directly from the command prompt (for starters, just try something as simple as CLS RED). There are many more graphical features that are available on the Maximite, so let’s begin by working through four of the demo programs to see some of these features. Graphics The Graphics.bas program is located in the root folder – run it with RUN Graphics.BAS (Enter). It demonstrates the speed of various Maximite graphics commands. It works through PIXEL, LINE and CIRCLE commands, and finishes with some nice animations using the BLIT command. Press any key to progress through the demonstration. As with all the programs, we recommend you look at the code to see how various commands are used. C16 Modes The Modes.bas program (in root) nicely demonstrates the four different screen modes available on the Maximite Practical Electronics | February | 2020 by showing them all simultaneously on one screen. The different modes allow you to balance speed, resolution, colour range and memory usage, as explained in the User Manual. For high-resolution (along with access to all eight colours), you would use MODE 3. For games, MODE 4 is recommended as the bigger pixels are processed faster, meaning onscreen objects move quicker – examine the code to see how different elements are drawn. More importantly, play with the code to alter effects using the User Manual to guide you. (To be clear, we are referring to screen modes here – not the Maximite’s three modes: Immediate, Editor, or Run.) BlitDemo BlitDemo.bas is a multi-file program, so first type CHDIR BlitDemo (Enter) and then RUN BlitDemo (Enter). To stop the program, press Ctrl-C. This will return you to the command prompt, with the SD card access still pointing to the BlitDemo folder (you can see this by typing FILES (Enter), after which you will see all the files that BlitDemo.bas uses). To return to the main folder on the SD card, type CHDIR .. (Enter). Typing FILES (Enter) will again show a list of all the demo programs / directories ready for you to try the next program. Follow this process for all multi-file demo programs. BlitDemo shows how some fantastic animation effects can be generated by using the BLIT command. Check out the colour mixing in the lower right corner. Why not try changing the colour of the ‘scrolling waveform’ to ensure you understand how the BLIT command works. (This program runs in MODE 3.) SprtDemo This is another multi-file program. SprtDemo shows how sprites (blocks of pixels) can be drawn on the screen without affecting the background. In this demo, little ‘Pacman ghosts’ wander over a bitmap (.bmp) image of a well-known landscape. See if you can change the background to one of your own – hint: use something like Microsoft Paint to save a .bmp file with the appropriate pixel resolution and colour depth. These four graphics demonstrations have shown you something new, and given you a chance to explore code and make changes. If you mess something up, simply re-copy the original program onto the SD card. Further demo programs Now take some time to try some of the other demo programs. One of the great things with MMBASIC is that it is easy to customise the code to suit your own requirements. Remember, all programs are written in BASIC – there is absolutely no machine code or complex C code! There are actually more programs in the download folder than shown here in the screenshots, so do be sure to try them all out. As you have just seen, some programs nicely demonstrate how to use the Maximite’s graphical commands, while other programs provide some mind challenges; for example, Tetris, Checkers, and Four-in-a-row. Plus, there’s a handful of action games, some that you can play straight away, and others requiring you to build a simple hardware controller (comprising a potentiometer and a button). Remember, the Maximite is easy to hook up to external hardware, and these particular games demonstrate the interaction between hardware and software in a fun way. Important note: if a multi-file program uses any .mod sound files then you may have to perform a manual process before the program will run correctly – see next section! All of the programs in the download folder have been collated from various authors around the world and we thank them all for making their code publically available. In some cases, the code has been written from scratch, specifically for the Maximite, whereas other programs are simply conversions of old BASIC code that was originally written for 80s home computers such as the BBC micro. If you look at the code, you will see that some incorporate line numbers. This raises an important point worth stressing – you can literally take any old BASIC program (with or without 43 FileMngr.bas – A simple file explorer utility. You use the arrow keys to navigate to a .bas program file (or a folder), and then press Enter to launch the program (or open a folder). Julia.bas – Generates a colourful image that is mathematically similar to the famous Mandelbrot set. Be patient, it takes about 15 minutes to completely generate the image. MoonLand.bas – Use the arrow keys to land your spacecraft on the landing pad. Ensure you land as gently as possible by minimising the speed. (Multi-file program – manually copy .mod files). HighIQ.bas – This version of the classic Solitaire game challenges you to remove all but one of the 32 counters. You can jump either horizontally or vertically by entering the grid reference numbers. Checkers.bas – This is another variation of solitaire, and is similar to HighIQ. However, in this version you can only jump in a diagonal direction, and there are more counters to remove. Sudoku.bas – Challenge yourself to this popular number puzzle. Try to populate the empty squares with digits 1-9 so that no digit is repeated in a row, column, or 3×3 cell. Three difficulty levels await. line numbers), and migrate the code to MMBASIC without too much effort. Drive B is the only other ‘drive’ on the Maximite, and this refers to the SD card itself. Drive B is the default drive when the Maximite is powered on (or reset). you (in code). The MUSIC demo program is a good example of this (it automatically copied T1.mod, T2.mod, and T3.mod into Drive A). However, other programs require you to copy the files manually. To understand if you need to copy the files yourself, just run the program, and see if an error message like ‘PlayMOD Error: Cannot find file’ appears – if so, you will need to do transfers manually. We will now work through the process involved by using the MoonLand demo program (which has three .mod files that need copying to Drive A). Begin by pointing to the MoonLand folder by typing CHDIR MoonLand (Enter), and then list the .mod files with FILES (Enter). Before we go any further, lets see the error message generated when the .mod files are missing from Drive A. Type RUN MoonLand (Enter), and press any key to start the game (you will then see a screen similar to the above screenshot). Press the UP arrow key and you will see an error message as the program is trying to play the ‘missing’ turbine.mod sound file. You will see large characters on the screen – so type MODE 3 (Enter) to return to normal size characters (ignoring any error message). Now type FILES (Enter) and you will .mod sound files Playback of a .mod sound file results in very impressive sound, as witnessed back in Part 2 when you tested your Maximite with the MUSIC demo. However, for the Maximite to be able to perform this task in the background, the data in a .mod sound file needs to be accessed very quickly by the PIC processor. Reading the .mod data directly from the .mod file on the SD card is just too slow, hence the .mod file needs to reside in (ie, copied to) the PIC’s ultra-fast memory. However, the amount of ultra-fast memory available is very limited, so if there are any existing .mod files from a previous program, then these files need to be deleted from the fast memory first to make space for new sound files. Otherwise, you will likely see an ‘out of memory’ message. The memory space where .mod files need to be placed is referred to as ‘Drive A’. To access this, type DRIVE A (Enter) and then type FILES (Enter) to see if any files are currently there. Note that the number of files, and the number of ‘bytes free’ are displayed. For completeness, 44 Deleting .mod files To delete a file from Drive A, use the KILL "filename" command (this causes the screen to blank temporarily). To gain the maximum possible space in Drive A for new files, the KILL command should ideally be repeated to delete each file until there are none left. You can check how many files are left by typing FILES (Enter) at any time. If you have been following this project, and if you successfully ran the MUSIC demo, then you will likely see T1.mod, T2.mod, and T3.mod listed. You should now delete these files to free up space. When no files are left, type DRIVE B to point back to the SD card (and then type FILES (Enter) to list the files and folders (<DIR>) stored on the SD card). Installing .mod files Once we have space in Drive A for new .mod files, we now potentially need to copy the files from the SD card to Drive A. ‘Potentially’, because some programs will actually do this automatically for Practical Electronics | February | 2020 FourRow.bas – The classic four-in-a-row program; in this version you play against the Maximite. Use the < and > keys to select a column, and then drop your counter by pressing the spacebar. MaxiTrek.bas – A retro game in which you travel the galaxy. You mission is to destroy the fleet of Arduitrons that have attacked your planet. Press I to see the keyboard controls. MaxiTrek – Pressing M displays a map of the galaxy. Navigate to different parts in order to attack the enemy. (The code automatically copies the .mod file into Drive A (and renames it title.mod)). Breakout.bas – This game is a variation of the classic breakout game but with a difference – you need to build a game controller! Details are provided at the start of the program code. Arcade.bas – An arcade-style game in which you need to shoot the enemy. Requires a DIY controller (potentiometer and button – see start of code for details). (Copy the two .mod files to Drive A). Invaders.bas – A copy of the classic Space Invaders game. This also requires the DIY controller (potentiometer and button – see start of code for details). (Copy the two .mod files to Drive A). see that the Maximite is pointing to Drive A (probably containing 0 files) – this is because the program crashed while trying to locate the turbine.mod file which needs to be in Drive A. So point the Maximite back to Drive B with DRIVE B (Enter), and then type FILES to list the files in the MoonLand folder. Next, use the COPY "source" TO "destination" command on each .mod file. Start with COPY "explode. mod" TO "A:explode.mod" (Enter). (The screen will go blank temporarily while the file is copied.) Copy the other two files with COPY "landed.mod" TO "A:landed.mod" (Enter) and COPY "turbine.mod" TO "A:turbine. mod" (Enter). Use KILL to delete any misspelt file names. When all three .mod files have been copied into Drive A correctly, type DRIVE B (Enter) to point back to the SD card. You can now type RUN MoonLand to play the game and this time you will not see the error message). Note: After running a multi-file program, ensure that you’re pointing to Drive B (SD card) and not Drive A (fast Maximite memory). To do this, use the command DRIVE B (Enter). Then use CHDIR .. to go up a level to see all the other demo programs, and folders (<DIR>) in the root folder. The above topic has been discussed in detail since several of the demo programs use .mod sound files and the program won’t run properly if there is not enough space in Drive A for the .mod files. In summary, there are possibly two tasks that need to be performed – clear space in Drive A, then (potentially) copy the .mod file(s) manually into Drive A. Once you have done this a couple of times, it will become second nature! Now it’s time for you to explore the other demo programs. Remember, there are more programs contained on the SD card than are shown here as screenshots. end the Colour Maximite Computer project with an example of software controlling some externally connected hardware. The example is based on the Blinkt! RGB LED module featured in this month’s Make it with Micromite (MIWM), and we’ll use the SPI command to control eight ultra-bright RGB LEDs. Before we start, please refer to Fig.2 in MIWM Part 2 (PE, December 2019) to see how to build a simple logic probe comprising an LED, 470Ω resistor, and some jumper leads. Next, assemble this simple (and useful) test device. You can check it works correctly by inserting the test probe onto either 5V or 3.3V (and the LEDs cathode to GND) – if the LED lights then all is good. If the LED does not light up, then first check the LEDs polarity, and also check the resistor is the correct value (or between 270Ω and 1kΩ). Practical Electronics | February | 2020 GPIO hardware control As we have often said, it is very easy to interface external hardware with the Colour Maximite Computer. The User Manual provides various examples on the commands used (especially SETPIN and PIN) so we won’t repeat that information here. Instead, we will explain how you address the 40 available I/O pins (20 external on the rear-panel connector, and 20 internal on an Arduino footprint connectors). We will The rear-panel connector At the back of the Colour Maximite Computer, there is a centrally mounted 26-way connector. This connector makes 20 GPIO pins available, along with GND, 3.3V and 5V power outputs. The pinout is shown in Fig.1 45 5 19 20 8 17 18 7 15 16 10 9 13 14 G n d 3 6 11 G n d 4 1 G n d 3 .3 V G n d 5 V 2 12 Fig.1. The pinout for the 26-way connector on the rear panel (as viewed outside box). It provides 20 GPIO pins (numbered 1 to 20) and also 3.3V and 5V power for powering external hardware. (as viewed when looking at the rear panel). The numbers in orange boxes are the pin numbers that are used to reference these twenty GPIO pins. If we connect the LED test probe to Pin 1 (the third pin along from top left) and the other end to GND, then to be able to control the LED with software, we would first need to configure Pin 1 as a digital output (DOUT) by using the command SETPIN(1),DOUT. Then, to turn the test LED on (set Pin 1 to a high logic level), you would use PIN(1)=1. Likewise, to turn it off, use PIN(1)=0. Use the test probe to confirm this works as expected. The Arduino connector Inside the case, you will see two 6-way, and two 8-way sockets that make up the Arduino footprint connector. Alongside each socket you will see the Arduino pin references highlighted on the silkscreen. This is shown in Fig.2, along with the pin numbers that are used to reference these twenty GPIO pins. If we were to connect the test probe to the lower left socket (marked D0), then in order to use software to control the LED we would first configure pin D0 (pin 21) as a digital output with SETPIN (21),DOUT. Note that with the Arduino pins we can also reference the pins by the silkscreen A 5 V IN G N D G N D 5 V 3 .3 V R E S A 0 27 26 28 29 31 D 9 D 1 0 D 1 1 D 1 2 D 1 3 G N D 25 24 D 8 D 5 23 35 D 4 D 3 D 2 D 1 D 0 21 22 36 37 D 7 38 39 D 6 40 A 1 A 2 A 3 A 4 A 5 A 4 30 33 32 34 Fig.2. The pinout for the 20 GPIO pins available on the internal Arduino connector. These pins are numbered 21 to 40, and can also be referenced by the ‘Arduino name’ (D0-D13, A0-A5). 46 legend – so SETPIN(D0),DOUT will perform exactly the same result. Then to turn the LED on, simply use either PIN(21)=1 or PIN(D0)=1. Likewise, to turn it off, use either PIN(21)=0 or PIN(D0)=0. Once again, go ahead and check that both these pin references work as expected to control the test LED. Now that we know how to address the 40 available GPIO pins (and where they are physically located), we next need to explain that some pins perform specific or special tasks. These pins (and their functions) are: Pin 12 = I2C Data (SDA) and IR receiver Pin 13 = I2C Clock (SCL) Pin 15 = COM1 Rx Pin 16 = COM1 Tx Pin 17 = COM1 RTS Pin 18 = COM1 CTS Pin D0/21 = COM2 Rx Pin D1/22 = COM2 Tx SPI and one-wire can use any digital I/O pin – the pin numbers are specified in the relevant MMBASIC command (as commented in the SPI example below). We recommend you work through some of the examples in the User Manual to get used to how to control hardware. And for readers following the Make it with Micromite (MIWM) series: a lot of the topics and projects covered in that series can be migrated to the Colour Maximite Computer with minimal change. However, there are two important points that need to be highlighted: 1. The Colour Maximite Computer is based on a 100-pin PIC micro-controller, whereas the Micromite is based on a 28-pin PIC. Therefore, the pin numbers quoted in the MIWM series will not apply to the Maximite. Instead, any external hardware will need to be connected to the appropriate Maximite pins. The MIWM code then simply needs to be updated (to reflect the new pin numbers) before it will run properly on the Maximite. This is much easier than it sounds. 2. MMBASIC can only connect to a single display. Since the Maximite has a dedicated VGA monitor for its ‘display’, no other external display can be added. Therefore, any program code for MIWM projects that incorporate the IPS display (or any other display) will need to be modified to write and draw to the VGA monitor instead. This will generally mean having to use different commands and/or parameters for the graphical commands. Have a look at the MIWM series and convert some of the projects to run on your Maximite. To help you get started, let’s modify parts of the Mood Light from this month’s article and control the RGB LEDs from the Maximite. Fig.3. The Maximite Mood Light is built around the Blinkt! module (see page 67) and is connected to the rear-panel connector via a short ribbon cable. A suitable adaptor board keeps everything tidy. Maximite Mood Light! Here’s a practical example, explaining how to connect a Blinkt! module to the Maximite and control it with a small program. We won’t repeat the Blinkt! operational details other than to say that we need four connections – 0V, 5V, SPI Data, and SPI Clock. Do read this months MIWM article to understand the SPI data that we need to send to the Blinkt! to control LED brightness and colour. We can connect the Blinkt! to the Maximite’s rear-mounted connector by using a short ribbon cable, and a breadboard to keep everything tidy. To make it easier to connect hardware to the rear-mounted connector, we recommend the use of a T-Cobbler module. The T-Cobbler simply allows a ribbon cable to be plugged into a breadboard. An alternative to the T-cobbler is something like that shown in Fig.3. The four pins we need to connect to on the Blinkt! are shown in MIMW, Fig.4, page 67. At the Maximite end, the positions of 0V and 5V on the rear-panel connector are shown in Fig.1. SPI Data and SPI Clock can be connected to any available I/O pin (the selection is specified in the SPI command). Here, we have chosen to use pins 2 and 3 respectively. Once these four connection have been made, we need to send 41 bytes of data to set a colour on the eight RGB LEDs (see Fig.6 on Page 67). We have written a very short program to do this – MoodLite.bas. Download and run it, follow the on-screen instructions and you should soon see some action on the LEDs. We will not explain the code in detail here – comments are scattered throughout the program. Try adding new features such as controlling colour with an IR remote control. A good exercise is to make the MIWM Mood Light software fully operational on the Maximite. This is not as daunting as it sounds, and as usual, if you need help, just drop me an email! Practical Electronics | February | 2020