Fullscreen HTML5Med Res (??MB)HTML4

Make it with Micromite Phil Boyce – hands on with the mighty PIC-powered, BASIC microcontroller Part 27: Having fun with a Micromite Plus – Part 2 L ast month, we prepared a piece of stripboard to form the basis of a fun Micromite Plus (MM+) project – driving an RGB LED matrix panel. Having made the appropriate track cuts, installed the relevant wire links and soldered all the connectors in place, we now need to check that the stripboard has been assembled correctly. So, this month we will begin by testing it, easily achieved by stepping one-by-one through each element of the project. As you will see, each step simply involves connecting the relevant item to the stripboard, configuring the MM+ as necessary, and then checking that the relevant element works as expected. This methodical manner of testing and configuration ensures that we end up with a fully working project. Once this is successfully completed, we can then download the program code to the MM+ to bring the RGB panel to life with a clock, temperature display and our version of the classic Mastermind game. Before we begin In this article, the terms ‘MM+’ and ‘E64’ both refer to the Explore 64 module. Likewise, the use of the term ‘computer’ refers to your machine (eg, a PC, laptop, tablet or Raspberry Pi) on which you are running a terminal application, for example TeraTerm. The E64 comes in a variety of different PCB versions. Thankfully, they all have identical pinouts (on the two long rows of header pins), and they all have a microSD socket, which means we can use any version of the E64 for this project. All E64 modules supplied by micromite. org include a mini-USB socket onboard, and this provides connectivity to your Micromite code The code in this article is available for download from the PE website. 62 computer via a single USB lead. In this scenario, the computer would be supplying the E64 with the required 5V. Fig.3 from last month’s article summarises the pinouts of the E64. Note the three pins associated with power (lowerright corner in the diagram), the middle one is labelled ‘5V’. When the E64 is connected to a computer via a USB lead, this 5V pin is effectively an output pin that can power hardware. However, this project will require more current than a computer’s USB port can supply, which is Fig.1. There have been six different versions of the typically limited to 500mA (or the Explore 64 PCB, but they all have the same more if using a USB-C port). The pinout (see Fig.3 from last month’s article). reason we require more current However, there are only two USB power link is that the RGB panel contains positions: 1) (upper photo) PCB topside, a jumper link, many LEDs (as discussed last or 2) (lower photo) PCB underside, a solder link. The month) and that’s why we need positions of the links are circled in red. to use an external PSU. So, by connecting the E64 via USB to or a solder link (underside), as shown in a computer, we are able to configure the Fig.1 above. MM+ and also load the relevant software, Understand that it is still possible for but the E64’s 5V output pin cannot drive the computer to communicate via USB more than a few RGB panel LEDs. even with the link removed, since it is only the 5V ‘wire’ that is disconnected whenever the link is removed. Simply Important: power warning! consider the link as only being required Returning to the E64’s 5V pin mentioned for initially configuring the E64 before the above; with care, this can also act as a power external 5V supply is connected. input pin. So, along with the adjacent 0V In summary, you must remove the USB pin, we can use these two pins to connect power link whenever the external 5V our external high-capacity 5V power supply. power supply AND the computer are both However, you must note the following. It connected simultaneously. is vital that you prevent any external 5V Once this project is up and running, we source from back-feeding to the E64’s USB recommend you keep the link permanently socket, which in turn would then supply removed. Should you need to make any 5V into any connected computer – this may software changes, then you can safely cause irreparable damage to the computer. reconnect your computer without any On each E64, there is a USB power link, danger of feeding back 5V. and for this project, it is very important to understand where it is located because we will need to add and remove it at Test steps various stages during testing. This link The following steps may appear lengthy, may be a traditional jumper link (topside), but don’t worry; although there is plenty Practical Electronics | April | 2021 to do, many steps are quick to perform and most concepts will be familiar to you. Step 1: Connect to the E64 First, we need to connect the E64 module directly to a computer so that we can use the terminal application to communicate with the MM+. Note that the E64 should not be plugged into the stripboard at this time (we will do that at Step 4). Also, the USB power link, as discussed above, must be installed. Use a mini-USB lead to connect the E64 to a spare USB port on your computer, launch your usual terminal application (eg, TeraTerm) and then select the correct COM port that your computer’s operating system assigns. Ensure that you can see the usual MMBASIC Command Prompt. Depending on the version of E64 that you have, you may see a power LED illuminate confirming that the E64 is powered up. At the command prompt, type OPTION BAUDRATE 115200 and then reset the MM+ by pressing the reset button on the E64. If you do not have a reset button, then simply remove the USB lead temporarily, and then reconnect to your terminal application. You may need to set the baud rate in your terminal app to reflect the new speed of 115200. Step 2 – Insert uSD card You will require a microSD (uSD) card for this project; and our advice is to use a branded one with a capacity of between 8GB and 64GB (Class 10 is fine). Smaller (or larger) capacities may not work, but one that meets the above conditions will likely work straight out of the packet if purchased new. If you are planning on using a uSD card that has previously been used, then Fat16 or FAT32 formatting is required. In this scenario, we recommend you use your computer to reformat the uSD card to wipe it clean (back-up any data first!). Gently inset the microSD card into the uSD socket on the E64. Be careful to insert it with the correct orientation; if it feels hard to insert, then chances are the uSD card is the wrong way round. On proper insertion, you will feel a ‘clicking’ action. Note that in order to remove the uSD card, you need to gently push on the uSD card, and it will once again ‘click’ to signify it is released. In other words, the uSD socket is a ‘push-push’ type, meaning push the uSD card to insert it, and push again to remove it. For the E64 to be able to access the uSD card, you will need to set an OPTION. However, it is worth checking first as the relevant OPTION may already be set. At the command prompt, type OPTION LIST and if any OPTIONs have been set, they will be listed here. You are looking for OPTION SDCARD 12,14. If you don’t Practical Electronics | April | 2021 see it listed then type it at the command prompt, press Enter and then reset the MM+. Now type FILES and on pressing Enter, it should respond with a list of directories and files on the uSD card (even though there probably won’t be any). Remove the SD card, and retype FILES and check that it responds with a message indicating that it cannot find the uSD card. Reinsert the uSD for now. If you make a mistake when setting the OPTION, for example, you accidentally typed an incorrect pin number, then simply type OPTION SDCARD DISABLE first, reset the MM+, then re-enter the correct parameters. Step 3 – Install the RGB panel display driver The concept for loading the display driver will be familiar to you if you have been following the MIWM series. We simply load a program (the driver) onto the E64 and then save it into the LIBRARY area of the MM+. With the MKC, we would have used AUTOSAVE (with copy/paste and Ctrl-Z), however, we now have access to a uSD card, which we can use instead. If your computer can access an SD card, then proceed with the following, otherwise use the AUTOSAVE method to load onto the MM+ the RGB_Panel_driver.txt file (available, along with this month’s other files, for download from the April 2021 page of the PE website). Remove the uSD card from the E64 and insert it into your computer. You may need an SD adaptor that makes the uSD appear as a full-size SD card; these typically come with any newly purchased uSD card. Download the RGB_Panel_driver.txt file, and copy it onto the SD card. Next, safely eject the SD card from your computer, and reinsert the uSD card into the E64. Upon typing FILES, you should see the file listed. At the command prompt, type LOAD “RGB_Panel_driver.txt” and on pressing Enter it will load it into the MM+. This can be checked by typing LIST or EDIT, or pressing F4 (which in effect is the same as typing EDIT). Once you have the driver code installed (either by AUTOSAVE or LOAD) we need to move it into the library area of the MM+. At the command prompt, simply type LIBRARY SAVE. This effectively keeps the driver code safely in the MM+ without the risk of it being erased by any future changes we make in the Editor. Note that if you are using an E64 which has previously been used with a different display, then we advise you type LIBRARY DELETE first to remove any potential conflicts (remember, the Micromite can only have one display driver installed at any one time). To check the (correct) driver is installed, type LIBRARY LIST at the command prompt and you should see a shortened listing appear. If not, repeat the above steps. This completes the installation of the display driver. Step 4 – Plug in E64 Begin by removing the USB lead from the E64. Next, carefully align the E64 module over the project’s stripboard (sockets JS2 and JS3) ensuring that the E64’s USB socket is towards the outer edge of the stripboard – see Fig.2. After fully inserting the E64, perform a quick visual check to ensure that all pins are located correctly. If you notice anything wrong, carefully remove the E64, and realign as necessary. Now reconnect the E64 to the computer with the USB lead, restart the terminal app and check you still have communication with the E64. If not, unplug the E64 from the stripboard, check app connectivity, and if you find you only lose connection when the E64 is inserted into the stripboard, then this implies there is an error on the stripboard somewhere. You will need to do a thorough check and correct any errors before proceeding. Once you have the E64 installed on the stripboard, and can communicate with it via your computer, you can move on to the next step. Step 5 – Plug in RTC With the E64 still connected to the computer, correctly install the RTC onto JP1 (refer to Fig.2 for orientation). Then, at the command prompt, type OPTION RTC 43,44 and reset the MM+. Now we need to set the time inside the RTC. To do this type RTC SETTIME yy,mm,dd,hh,mm,ss at the command prompt, replacing the six parameters with the correct date and time information. On pressing Enter, the parameter values typed will be stored. So, to set the RTC to 01:22:30 pm on 5 March 2021 you would type: RTC SETTIME 21,03,05,13,22,30 (remember to use 24-hour clock values for the hours). To test the RTC is working correctly, power down the MM+ for a short while, power back up, then type PRINT TIME$ to check that the time is maintained. If it shows a time of just after midnight (for example something like: 00:00:08) then you will need to check the RTC and associated links/ tracks on the stripboard as this implies the time is not being maintained (unless you are doing this test just after midnight!). Type OPTION LIST to check you used the correct pin numbers (43 and 44), if not, then type OPTION RTC DISABLE, reset the MM+, and then re-enter correctly. If this is correct but the time is not maintained, then check the RTC is inserted correctly. If it still fails to maintain the time then you have a track or wire link error (and do check for shorts too). Once you see the correct time maintained, you can move to the next step. 63 Step 6 – Plug in IR receiver Next, insert the IR receiver with the correct orientation into JS1 – the IR ‘bump’ on the main part of the body needs to be facing outwards (refer to Fig.2). Now, download the IR_Test.txt program and load it on to the MM+ with either the AUTOSAVE method (copy/paste) or the LOAD method (uSD card). Then RUN the program and check that you see numbers appear in the terminal screen whenever you press buttons on your preferred remote control transmitter. If you don’t see any numbers, check the circuit around JS1, and also check that you have the IR receiver inserted the correct way round. If still no numbers appear, then try a different remote control. Once you see a number appear on the screen whenever you press a button, you will need to make a note of the exact numbers that are associated with the seven buttons that we will use to control the main program. These are the KeyCode values, something we discussed back in Part 5 of this series (June 2019). We will need the following buttons for controlling the RGB panel: Up, Down, Left, Right, OK, Menu, and Play. Choose the buttons on your IR remote control that closely match these functions and make a written note of the KeyCode numbers that appear. Press each button multiple times to ensure the number displayed is consistent. We will use these KeyCodes in the next step when we modify the program code. Step 7 – Prepare program files and remove E64 Before removing the E64 module from the stripboard, we will first load the main program onto the MM+ and configure it with the KeyCode values noted in Step 6. Download the file RGB_ Panel_MainProgramv1.txt and load it into the MM+ using the SD card and LOAD method. At the same time, copy the three bitmap files (.bmp) to the SD card. Then use the Editor to modify the first few lines of code to reflect the KeyCode values noted above – the comments in the code will make this self-explanatory. Press F1 to save the KeyCode modifications, and then type RUN to check no errors appear on the screen. You should see four pairs of numbers appear on the screen and then nothing will appear to happen. If you see this, then all is good. Now disconnect the E64 from your computer by totally removing the USB lead, and then carefully unplug the E64 module from the stripboard. This will allow us to connect (and test) the external PSU without risking the E64 module. Important: once the E64 is unplugged from the stripboard, remove the USB power link. Step 8 – Connect RGB panel The RGB panel comes with a short ribbon cable and also a power cable – these are both required for connecting the RGB panel to the stripboard. Referring to Fig.1b from last month, first insert one end of the ribbon cable into the left-hand 2×8way connector on the back of the RGB panel. Then insert the power cable’s connector into the power socket on the rear of the panel (located in the photo just to the right of the central ‘chassis bar’). Both connectors have a ‘key’ on them to ensure they are inserted with the correct orientation. Next, insert the other end of the ribbon cable into SK2 on the stripboard. If you have not used a shrouded socket for SK2 (and instead used 2×8 pin headers) ensure that you get the cable orientation correct (refer to Fig.2). Next, insert the black power leads into screw terminal SK1 (hole position B36), and the red power leads into SK1 (hole position B34). Perform a quick test to ensure that both ends of these two leads are fully inserted and screwed in tightly. Step 9 – External power supply It is now time to connect the external power supply into screw terminal SK3. If using the recommended Raspberry Pi 4 official power supply, cut off the USB-C connector as close as you can 64 Fig.2. The Explore 64, RTC, IR receiver and optional Bluetooth module are shown here – note the correct orientation of each. to the connector (ensuring you unplug the PSU first!) and then strip the ends of the two cables in preparation for inserting into SK3. Ensuring the prepared ends are not shorted, power it up and carefully use your test equipment to identify which is 0V, and which is 5V. Unplug the PSU again, and then screw the identified 0V lead into SK3 (hole position W36), and the 5V PSU lead into hole position W34. Once the two PSU leads are screwed in tight, perform a quick visual test to make sure there are no shorts, and then power on. You may see the RGB panel flash brightly, and some LEDs may illuminate (this is fine); however, it is now important to do a quick voltage reading across both screw terminals to check that a reading of 5V (or slightly higher) is observed. If it is significantly lower than 5V then power down immediately and thoroughly check everything. Once you observe 5V across both screw terminals then you are ready to reinstall the E64. Step 10 – Plug in, switch on We are nearly finished, but before proceeding, please ensure the following two points are observed, First, the USB power link on the E64 is removed; and second, the external PSU is unplugged (at the mains). When both of these conditions are met, carefully reinsert the E64 module with the correct orientation. Check all the pins are inserted correctly, and then plug in the external PSU. If all is good, you should see the time and date displayed on the RGB panel (similar to that shown in Fig.2 last month). If the display remains blank, then connect your computer (USB power link must be off), and try to establish a connection with your terminal application. If you can establish a connection, and you are seeing the command prompt, then type RUN and you should see the RGB panel come to life. If you see nothing, try pressing Ctrl-C just in case the program is already running. Then at the command prompt, type CLS RGB(RED) and see if the panel turns red. If it doesn’t, then you have a connection error somewhere and you will need to thoroughly check every wire link and track associated with the 2×8-way socket, SK2. Check also that the ribbon cable is positioned correctly at SK2, especially if you’re only using 2×8-pin headers as opposed to a 2×8 shrouded header. At this stage, you should now have the time and date on the display, with the flashing time ‘colon’ between the hours and minutes. If so, proceed to the next step, otherwise if you are stuck, then take two high-resolution photos of both sides of your stripboard, and email them to me with a brief description, and I will help you diagnose the issue. Practical Electronics | April | 2021 Fig.3. a) (left) The main menu screen that is displayed upon pressing the menu button; b) (middle) the Mastermind game in action; and c) (right) the 64×32 file (named pic1.bmp) stored on the uSD card is displayed when the ‘Demo’ function is chosen from the main menu. Step 11 – Optional Bluetooth Back in Part 14 (March 2020) we discussed how to ‘set your Micromite free’ by using a pair of HC05 Bluetooth (BT) modules (or just one if your computer had built-in BT). If you have followed this series and implemented BT, then you can use the ‘receiving module’ and insert it directly into socket JS4. The component side of the HC05 should be facing the E64. With the HC05 correctly inserted, connect your terminal application (set to 115200 baud rate) to the BT module and you can now access the RGB Panel remotely. This is very useful for making ‘tweaks’ to the project as you can leave it in situ, and don’t have to insert a USB lead. Finishing off One thing you will notice is that the LEDs are very bright, so (ideally) we need a modification to make the RGB panel more pleasant (and easier) to read. This can easily be achieved by using a piece of LED-friendly acrylic positioned immediately in front of the RGB panel – the end result can look very professional. Ideally, the RGB panel needs to rest up against the acrylic for best affect. Examine Fig.2 from last month’s article, you can see that we have used a piece of ‘smoked’/tinted acrylic to ‘diffuse’ the LEDs. We used a black wooden photo frame, which also houses the electronics. The photo frame we used was just a lowcost one which had some depth to it (we removed the glass). We will not go into the precise details of assembly here as your mechanical and woodwork skills are no doubt superior to ours! We are Questions? Please email Phil at: contactus<at>micromite.org Practical Electronics | April | 2021 just making this suggestion to finish of the project so that the display looks good. Using the software We will not go into code details here, but we will briefly cover the features that are built into the program. When first powered up, the program shows the date, time and temperature. Pressing the assigned ‘Menu’ button will take you to the menu (see Fig.3a). Use the Up and Down buttons to navigate to one of the three options and press OK or Play to select the highlighted function. In the Mastermind game (see Fig.3b), use the Left and Right buttons to navigate to the colour peg that you’re guessing, the Up and Down buttons to change the colour of the peg, and the OK or Play buttons to enter your guess. The ‘Demo’ function will display any 64×32 bitmap file named pic1.bmp that is stored on the uSD card. We have made a bmp file available for download (see Fig.3c) – simply copy this onto the uSD card. This project has shown you how to drive a 64×32 RGB LED panel, incorporate an RTC module and use an IR remote control for navigating functionality – here, a clock, a simple game, and displaying a bitmap image stored on the uSD card. There is so much more that you could do with this hardware – remember, it is the software that makes the project behave in the manner it does. No doubt you could suggest several software improvements to what has been presented here, or even have your own ideas for a totally different project that is based on the same hardware. Maybe you could even mount it in an unusual enclosure that suits your specific requirements. Competition To encourage you to get involved, we invite you to build your own version of this two-part project and then enter it into our RGB Panel competition for a chance to win an amazing new Colour Maximite 2 computer (the latest version – to be featured in PE very soon). Your entry could be an exact copy of what has been presented here, or maybe a software improvement. Alternatively, you may want to include some additional hardware in order to expand on (or totally change) the overall functionality. All we ask is that your entry must at least use all the electronic hardware that has been used here. As this may take you some time to complete, we have a closing date of 1 July 2021. Simply email us with a brief description of your entry, along with a few photos of your build. A single prize of a Colour Maximite 2 computer will be awarded to the best presented design. In addition, three £75 vouchers for use at micromite.org will be given to three lucky entries chosen at random. Next month This simple-yet-fun project has nicely demonstrated that by using a 64-pin Micromite Plus instead of the standard 28-pin Micromite it is possible to incorporate more powerful functionality and features into a project. However, don’t forget that the 28-pin Micromite can still achieve some extremely impressive results. Next month, we will return to the MKC and connect it to the popular and versatile ESP32 Wi-Fi module. By doing this, it becomes possible to extract data from the Internet; for example, accurate time information from an NTP server, or local weather information for displaying on a connected display. Until then, have lots of Micromite-based fun! 65