Fullscreen HTML5Med Res (??MB)HTML4

Make it with Micromite Phil Boyce – hands on with the mighty PIC-powered, BASIC microcontroller Part 38: How to build a PicoMite BackPack L ast month, we showed how easy it is to load the MMBASIC firmware into a £4 Raspberry Pi Pico. The result – a ‘PicoMite’ – is an extremely powerful module that Micromite code The code in this article is available for download from the PE website. 40 offers 26 I/O pins. Since it is based on the Micromite Plus firmware, it has all the features of a MicroMite Plus, which means there are many additional graphics commands available to the user compared to a standard Micromite. Furthermore, there are also commands that allow connection to an SD card, enabling storage of program, data, image and sound fi les. However, to be able to take advantage of these features we Fig.1. Some of the available Pico plugin display modules that can be used to create a PicoMite BackPack. The screens vary in size from 0.96-inch to 3.5-inch (with different screen-resolutions) and come in a variety of technologies including standard LCD, high-clarity IPS and low-power OLED. need to add a suitable display and SD socket to the PicoMite. This is where we can be smart and take advantage of the many readily available low-cost display modules that are designed to be plugged directly onto a Raspberry Pi Pico. By connecting an appropriate display module (preferably with an onPractical Electronics | August | 2022 Display module choice Fig.2. The Waveshare Pico-RTC-DS3231 is a high-accuracy Real-Time-Clock module; perfect for adding to a PicoMite BackPack. It has pins and sockets so it can easily be sandwiched between the PicoMite and the display module. board SD socket) we effectively create a PicoMite BackPack. As we’ll see, not only is the PicoMite BackPack much more powerful than the standard Micromite BackPack, but also it is much cheaper, and because no soldering is required, it is also much quicker to get a project up and running. A point worth noting here is that many of the available Pico display modules are based on IPS screen technology, which means superior image quality – higher contrast and a wider viewing angle than the screens commonly used with the standard Micromite BackPack. As a bonus, there is nothing stopping us from also using many of the other types of plug-in Pico modules with our PicoMite (ie, non-display modules). This is a great way to quickly (and often very cheaply) add a variety of other features to the PicoMite. For example, there is a high-accuracy Real-time Clock (RTC) module available based on our favourite RTC chip, the DS3231 (see Fig.2). An RTC is a useful addition to the PicoMite BackPack, so later in this article we’ll show you just how easy it is to add one. There are many different plug-in display modules available for the Pico (see Fig.1). The three fundamental parameters determining display choice are the physical screen size, the shape and the pixel resolution. Many of these displays can work directly with the PicoMite thanks to MMBASIC having various built-in display drivers, but do remember that as with any other Micromite, only one display can be connected to a PicoMite at any one time. To create a PicoMite BackPack, all you need to do is choose a display for your project, connect it to the PicoMite, and then set a few OPTIONs at MMBASIC’s command prompt (with the parameters dependent upon the display module chosen). To demonstrate this, we will discuss how to set up two different PicoMite BackPacks; one with a 2.8-inch 320x240 touchscreen (identical size and resolution to a standard Micromite BackPack) and the other with a 3.5inch 480x320 touchscreen. Note that the process we use to create a BackPack applies to any of the compatible display modules; it is just the OPTIONs parameters that vary. Latest PicoMite Firmware Since last month’s article, a new version of the MMBASIC Firmware (v5.07.04) has been released. The required file (PicoMiteV5.07.04.uf2) is available for free download from the August 2022 page of the PE website (along with the updated PicoMite User Manual). We advise you to keep your PicoMite updated with the latest version of MMBASIC as this means you will have access to any new commands or features that are introduced, plus any bug-fixes. An alternative source for PicoMite firmware updates is via Geoff Graham’s website (www.geoffg.net/picomite.html). If you scroll to the Downloads section near the bottom of the page, you will find both files there, along with a text file containing a list of known bugs. You can also find the beta version of the next PicoMite firmware (currently v5.07.05b9). It is the most stable version of any beta software I have ever come across – credit to Geoff Graham and Peter Mather! So, update your PicoMite to ensure you’re running at least MMBASIC v5.07.04 (or v5.07.05b9). Remember that if you already have MMBASIC installed on your Pico module, then you can use the MMBASIC command UPDATE FIRMWARE to bring up the Pico’s Flash drive (where you place the relevant .uf2 file). However, if it is a brand new (blank) Pico module, then hold down the ‘BOOTSEL’ button while powering up the Pico – see last month in Part 37. Pico Expander module Before we begin creating our first BackPack, we want to alert you to a type of module that is useful when experimenting with a PicoMite. This is the ‘Expander’ module which allows multiple Picocompatible plug-in modules to be used simultaneously by extending all the Raspberry Pi Pico’s pins to multiple sets of pin headers (the Pico is plugged into one socket header set). Expander modules typically allow two or four plugin Pico modules to be used – see Fig.3. Regardless of size (and shape), these Expander modules are also very useful as they provide quick and easy access to all I/O pins. By using the popular Dupont style jumper leads (with a female connector at one end for plugging onto the relevant Expander pin), the other end of the lead (if male) can then be inserted into a breadboard, or alternatively (if male or female) the other end can be attached to a socket or pin on another non-Pico module (as we will see later when using a low-cost, non-Pico RTC module). So, even though an Expander module is not required to make our BackPack, do get one. It will be useful when you tinker with your new PicoMite projects. Make sure you also have a selection of Dupont leads (female-male, and female-female). We prefer leads that are approximately 20cm in length; and have never suffered any issues with peripherals failing to work due to impacted signal timing. Now that we’ve updated the firmware, let’s create a BackPack. Fig.3. Pico Expander modules are available from different suppliers. Typically, they can connect either two or four Pico plug-in modules to the Pico. They also provide easy access to all I/O pins, which are clearly marked on the silkscreen. Practical Electronics | August | 2022 41 Fig.4. The Waveshare Pico-ResTouch-LCD-2.8 display module incorporates a 2.8-inch IPS touchscreen with a resolution of 320x240. It also an on-board micro-SD socket (perfect for making a PicoMite BackPack). 2.8-inch (320x240) BackPack What we will create is an alternative to the standard 2.8-inch Micromite BackPack. We will use a display module from the popular online manufacturer Waveshare. The specific module is the Pico-ResTouch-LCD-2.8 (see Fig.4). If you search online for this exact model, you will soon find a supplier that has them in stock; typical cost is around £14.50 plus delivery. For readers who are interested in a detailed description of the module, visit: www.waveshare. com/wiki/Pico-ResTouch-LCD-2.8 The only information that we really need to understand from the datasheet is the pin-out information – see Fig.5. The reason for showing it here is that it will help us to define the correct parameter values when setting OPTIONs. Now connect this specific display module to your PicoMite, either by plugging the PicoMite directly into the display (Fig.6a), or by using an Expander module (Fig.6b). Next, connect your PicoMite to your Terminal Application (ie, TeraTerm), and at the command prompt, work through the 12 steps shown below. (Note that the PicoMite is reset after setting an OPTION that saves parameters to memory, so you may need to press the Enter key to get Fig.5. The pin functionality and numbering used on the Pico-ResTouch-LCD-2.8. This information is used to define what parameter values need to be entered in the various OPTIONs that require setting. 42 the command prompt to appear again after the PicoMite has reset). 1. Start by clearing any exiting OPTIONs that have been set by typing the command: OPTION RESET 2. To check there are currently no OPTIONs set (or have just been cleared from step 1), type the command: OPTION LIST (this should return no OPTIONs – if you see any listed, simply type OPTION RESET again). 3. Set the PicoMite to run at its current maximum speed of 252MHz (this is not a requirement for the display module, but it is worth doing so that your PicoMite can perform optimally). To do this, type: OPTION CPUSPEED 252000 4. Next, we need to define the pins used for the SPI bus (the bus used to communicate with the display). We do this by using the command: OPTION SYSTEM SPI clk_pin, mosi_pin, miso_pin (replace the three parameters shown in italics with the relevant pin numbers). Fig.5 shows this is entered as: OPTION SYSTEM SPI GP10, GP11, GP12 5. To set the display driver, we use the command: OPTION LCDPANEL controller, orientation, DC, RESET, CS, backlight (replace the parameters with the relevant values). The controller used in this specific display module is the ST7789 (not the more familiar ILI9341). Refer to the PicoMite User Manual and you will see that there are various displays that use this controller (each with a different pixel resolution). To distinguish between the different ST7789 display modules, we add a reference to the horizontal screen resolution, so the controller parameter we need to use becomes ST7789_320. We will use Landscape (L) orientation, although we Practical Electronics | August | 2022 Fig.6. a) (left) Here, the 2.8-inch display module is shown attached directly to the PicoMite, resulting in a compact PicoMite BackPack. Ensure the PicoMite is oriented correctly (note: the display module’s silkscreen highlights which end to align with the Pico’s USB socket). Fig.6. b) (right) Alternatively, the display module and PicoMite can be connected together using an Expander module. deviation will be reported, but, if necessary, repeat this command until you have near to zero deviation. If this sounds complex, don’t worry, simply touch the crosshairs that appear on the screen, and then check the result displayed after all four Fig.7. Once the PicoMite’s OPTIONs have been corners have been touched. If set, it is worth typing OPTION LIST to check all either the X or Y value returned parameters have been set correctly (here, the 2.8is higher than 5, then calibrate inch settings are shown). again. With a stylus and a steady hand, you can get zero deviation. 9. To check the touchscreen calibration, can choose portrait (P), reverseuse the command: GUI TEST TOUCH landscape (rl) or reverse-portrait and then use a stylus to draw on the (rp). Therefore, with reference to screen. You should see the pixels Fig.5, we set the display driver with: turning on at the point of contact – if OPTION LCDPANEL ST7789_320, not, go back and repeat step 8. Press L, GP8, GP15, GP9, GP13 any key to exit this touch-test. 6. To check the screen is set up correctly, 10. Next we will set up the SD socket by use the command: G U I T E S T using the command: OPTION SDCARD LCDPANEL (which displays the usual SD_CS[, CLK, MOSI, MISO]. For test animation of randomly placed, this display module, we only need to randomly sized, coloured circles). define the SD_CS pin number, hence Press any key to stop it. If you don’t with reference to Fig.5, this is entered see this, then use OPTION LIST to as: OPTION SDCARD GP22 display the OPTIONs that are set, and 11. To check the PicoMite can read an SD carefully check all of the parameter card, carefully insert a micro-SD card values. If you spot an error, simply into the socket which is mounted on type: OPTION LCDPANEL DISABLE the back of the display module. Use to delete the OPTION, and re-enter it an SD card that has between 4GB again with the correct values. and 32GB capacity, and formatted in 7. To set up the touchscreen, we need to use the command: OPTION TOUCH T-CS, T_IRQ [,beep]. The optional beep parameter is not used here as the display module does not have an onboard beeper (you could add a beeper to any available I/O pin, and define this pin number as the beep parameter). Again, with reference to Fig.5, the command is entered as: OPTION TOUCH GP16, GP17 8. Next, calibrate the touchscreen with the command: GUI CALIBRATE. Simply follow the on-screen instructions – touch each corner in turn with a stylus (plastic gives best accuracy and least wear to the screen’s touch-overlay). If calibration is performed successfully, minimal Practical Electronics | August | 2022 either FAT16 or FAT32. Then type the command: FILES to display a list of any files and/or folders that are on the SD card. If you see the message ‘SD Card not found’, then chances are you have entered an incorrect parameter value (or not fully inserted the microSD card). Check the parameter value by using OPTION LIST, and if necessary, use OPTION SDCARD DISABLE to delete the OPTION, and then repeat step 10 to re-enter it correctly. 12. As a final check, if you type OPTION LIST you should see exactly the same OPTION parameter values as shown in Fig.7 (but probably five different parameter values shown against GUI CALIBRATE) Once you have successfully followed the 12 steps above, congratulate yourself; you have just created a working 2.8-inch PicoMite BackPack. 3.5-inch (480x320) BackPack We will now describe how to set up a PicoMite BackPack that uses a bigger 3.5-inch touchscreen, and which has a higher pixel resolution. For this, we will use another display module from Waveshare, the Pico-ResTouch-LCD-3.5 (see Fig.8). Note that the typical price for the 3.5-inch display module is £18.50 (so Fig.8. The Waveshare Pico-ResTouchLCD-3.5 display (top left and above) is similar to the 2.8-inch model (lower left), apart from being slightly bigger and having a higher pixel resolution (480x320). 43 Fig.9. The pin functionality and numbering used on the Pico-RTCDS3231. This information is used to define the I2C parameters (SDA and SCL) that need to be entered for OPTION SYSTEM I2C. just £4 more than the smaller 2.8-inch). Again, more details about this display module can be found at: www.waveshare. com/wiki/Pico-ResTouch-LCD-3.5 Rather than discuss the process step-by-step, we will instead simply summarise the 12 steps required (which are essentially identical to the steps performed above for the 2.8inch BackPack). 1. OPTION RESET (clear any previous OPTIONs that were saved) 2. OPTION LIST (check all OPTIONs have been cleared) 3. OPTION CPUSPEED 252000 (run PicoMite at 252MHz) 4. OPTION SYSTEM SPI GP10, GP11, GP12 (configure SPI bus) 5. OPTION LCDPANEL ILI9488W, RL, GP8, GP15, GP9, GP13 (configure the specific display module – note: use reverse-landscape orientation with this display module) 6. GUI TEST LCDPANEL (check screen set up correctly) 7. OPTION TOUCH GP16, GP17 (configure touch) 8. GUI CALIBRATE (calibrate touch) 9. GUI TEST TOUCH (check touch calibration) 10. OPTION SDCARD GP22, GP5, GP18, GP19 (configure SD socket – note: we need to define the SPI pins with this display module) 11. FILES (check SD card) 12. OPTION LIST (check that all OPTIONs parameter values are correct). Once you have successfully followed these twelve steps, you will have a working 3.5-inch PicoMite BackPack. Steps for using other displays From the above two examples describing the steps required to set up a BackPack, you will see that there are only four steps (4, 5, 7, and 10) that need changes to parameter values, depending on the specific display module being used. Refer to the display module’s datasheet for the relevant pin numbers, and the type of display controller used (ie, the equivalent of Fig.5). Once you have done this a couple of times, you will find that to set up a brand new PicoMite BackPack will take no more than five minutes (and that includes loading the firmware onto a ‘new’ (ie, blank) Pico). Yes, it really is that quick to set up a powerful PicoMite module with a choice of display size that matches your project’s requirements. Adding an RTC We will now show how easy it is to add an RTC to the PicoMite BackPack. For this, we will use yet another module from Waveshare; the Pico-RTC-DS3231 (see Fig.2; and for further details, visit: www. waveshare.com/wiki/Pico-RTC-DS3231). One thing to point out here is the cost – it is typically around £9.50 which by itself isn’t too bad, but when compared to the cost of the Pico module, the RTC costs almost three times as much! Anyway, let’s proceed on the basis that we can indeed afford this particular RTC module (although do see the next section if you have an alternative DS3231 module available). The pinout of the Waveshare RTC module is shown in Fig.9; again, it will be a useful reference to help understand the parameter values that we use in the single OPTION that we need to set. Begin by physically connecting the RTC; this can be done by either sandwiching it between the PicoMite and the display module (Fig.10a), or by inserting it into an Expander (Fig.10b). There are just four simple steps to complete the configuration of the RTC (including testing that it works correctly): 1. First, we need to define the pins used for the I2C bus (the bus used by the DS3231 RTC module). To do this, use the command: OPTION SYSTEM I2C SDA_pin, SCL_pin Referring to Fig.9, you will see that the command and parameters need to be entered as: OPTION SYSTEM I2C GP20, GP21 2. Next, we need to set the Date and Time in the RTC module with the command: RTC SETTIME year, month, day, hours, minutes, seconds If the date is 3 July 2022, and the time is 4:45 pm, then the command would be entered as: RTC SETTIME 22,7,3,16,45,00 (check with an Internet-based clock: https://time.is). When you press Enter for the above command, the precise date and time values will be sent to the RTC module; and the RTC will manage them until either the RTC SETTIME command is used again, or the RTC’s onboard battery is removed (or expires – although it should last many years before it needs replacing). Note that if you see an error message along the lines of: ‘RTC not responding’, then this means one of two things: either Fig.10. a) (left) The Waveshare Pico-RTC-DS3231 sandwiched between the PicoMite and the display module; b) (right) The Waveshare Pico-RTC-DS3231 inserted into a quad Expander module. 44 Practical Electronics | August | 2022 Fig.11. This is a low-cost alternative RTC module. The four labelled pins need to be connected to the PicoMite (see text). the RTC is not inserted correctly (check it’s not rotated 180°!), or the I2C parameters are incorrect (check by using OPTION LIST and make sure that GP20 and GP21 have been correctly entered). 3. Once the RTC’s date and time have been set up, there is one more OPTION that we advise setting: OPTION RTC AUTO ENABLE – it will force the firmware to upload the correct date and time from the RTC into the two MMBASIC system strings: DATE$ and TIME$. This ‘upload’ is performed automatically whenever the PicoMite is initially powered up, and thereafter every hour. 4. To test the RTC has been set up correctly, simply remove power from the PicoMite, then reconnect power (the easiest way to do this is to remove one end of the USB lead that connects the PicoMite to your computer, then reinsert it). Then, at the command prompt, type: PRINT DATE$ followed by PRINT TIME$. On pressing the Enter key, you should see the correct date and time returned. If not, check the RTC’s battery! Note that if the RTC is disconnected from the PicoMite Fig.12. The alternative lower-cost RTC cannot be plugged directly into the PicoMite, so an Expander module and four Dupont leads are used to connect it. Practical Electronics | August | 2022 (when OPTION RTC AUTO ENABLE is set), then the attempted ‘upload’ will result in an error message (‘the RTC cannot be seen’) and this OPTION will also be automatically disabled. In addition, if this situation arises at the time of an hourly ‘update’ and while a program is running, the program will stop, and the error message displayed. After following these four steps, you’ll have a fully functioning PicoMite BackPack complete with an RTC. However, as mentioned above, you may already have a different type of RTC module, so let’s see what alternative steps you need to set one up. Using a non-Pico RTC Let’s use the cheaper (£2) RPi mini DS3231 module (see Fig.11). There are just four connections we need to make; two for power (3.3V), and two for I2C communication (SDA and SCL). This RTC module has a 5-way socket, so we’ll use four female-male Dupont leads. The datasheet for the DS3231 shows that the RTC can run at either 5V or 3.3V; however, it is important that we use 3.3V when connecting it to the PicoMite. As mentioned last month, the maximum input voltage to any PicoMite pin is 3.6V, and if we accidently power the RTC with 5V, then the I2C pins (being pulled high by default) will also be at 5V. To eliminate any risk to the Pico module, ensure you connect the RTC power pin (labelled ‘+’) to the Pico’s 3.3V output pin. In last month’s Fig.7, the 3.3V pin on the PicoMite is the fifth pin down from the top-right corner (pin 36). For the GND connection, there are several 0V pins to choose from; for example, the third pin down from the top-right corner (pin 38). To make the two I2C connections we will use the same pins on the PicoMite as used in the example above for the RTC Pico module. Hence GP20 is connected to the RTC’s SDA pin (labelled ‘D’), and GP21 to the RTC’s SCL pin (labelled ‘C’). The four connections between the RTC module and an expander module are shown in Fig.12. Note that the pins are ‘flipped’ on the pin-headers so that the left-hand row (in a set of header pins) is essentially the right-hand row on the PicoMite; simply follow the silkscreen printed legends on the expander module – they are clearly marked (this is exactly why we find an Expander module so useful for tinkering). In Fig.12, the coloured leads are as follows: yellow = 0V, purple = 3.3V, blue = SDA, and green = SCL. Now that we have connected the RTC to the PicoMite, we can configure the PicoMite to use it. We have used the same I2C pins as in the previous example, so you can follow the same four steps to configure, set, and test the RTC module. So, now perform the four steps to ensure everything works as expected. RTC demo software We have made a short demo program (RTCdemo.txt) available for download from the August 2022 page of the PE website. It displays the day, date and time on your BackPack’s screen (see Fig.13). Note that as supplied, it can be used on any screen that has a horizontal pixelresolution of at least 320 pixels; hence it is ideal for either the 2.8-inch or 3.5inch BackPack described in this article. That said, it is very easy to follow what is happening in the code, and so it can be modified to run properly on different sized (ie, smaller) screens. Do test it on your new RTC PicoMite BackPack, it demonstrates how, with just three low-cost modules and a few lines of MMBASIC code, you can quickly create a working solution; in this case an accurate clock – you can never have too many clocks! Summary This month, we have given you the tools to create a PicoMite BackPack. All you need is the PicoMite created last month, to which you add a compatible display of your choice, set up with the relevant OPTIONs. In addition, you should also understand how to use other readily available plug-in Pico Modules with a PicoMite – it is just a Fig.13. The RTCdemo.txt program in action (running on a PicoMite that has been assembled on a quad Expander module). 45 quickly do ‘proof-of-concept’ tests. Note too, it is possible to build a complete project without soldering (not what you would expect to read in an electronics magazine), however, the main point we’re stressing here is that the PicoMite BackPack is a powerful building block that you can use in virtually any project – whether that project requires a soldering iron, or not. Pico-Eval-Board The 3.5-inch screen used on the 3.5-inch display module discussed above is also used on the Pico-EvalBoard (see Fig.14). This Pico module contains many useful components, such as a buzzer, a mini-button, a photoresistor for measuring light level, an RGB LED (W2812B), a 9-axis motion sensor (ICM20948), a LiPo battery header (complete with recharging circuit), and a reset button (which, is also present on the two display-modules discussed earlier). For more Fig.14. As well as having a 3.5-inch IPS touchscreen and a micro-SD socket onboard, details, visit: www.waveshare. the Pico-Eval-Board has additional components. It is the perfect display for building an com/pico-eval-board experimental PicoMite BackPack. Fig.15 shows the pin numbers used to connect to the various onboard identifying the connections available on matter of understanding the pin-numbers components. It is shown here to inspire the module being used. used on the module being attached, anyone opting to use this module in It’s worth searching online to see what and setting any OPTIONs accordingly. their BackPack to access some of these other Pico modules exist, and if any of Furthermore, you are not limited to using other components. For example, take a them could assist you in quickly creating plug-in Pico modules as we saw when we look in the User Manual at the BITBANG your next project idea. By using modules hooked up a mini RTC module; again, WS2812 command to see how easy it is (and Dupont leads), it allows you to it is just a matter of understanding and to control the RGB LED. And for anyone up for a challenge, try reading data from the 9-axis motion sensor! The cost of this module is typically around £29.50, which at just £11 more than the 3.5-inch display module, represents good value for money. (It is the actual module used in the photos in this article showing the 3.5-inch PicoMite BackPack.) Next time At the time of writing, I am still waiting for various Pico modules that should have been delivered by now – the world’s silicon supply chains are still recovering. So, at this point, the next topic depends on the postman! However, I can confirm that we will be using some more Pico modules to make something fun and interesting. Until then, stay safe, and have FUN! Fig.15. The pin functionality and numbering used on the Pico-Eval-Board. Refer to this (and PicoMite User Manual) to see if you can interact with some of the additional components. 46 Questions? Please email Phil at: contactus<at>micromite.org Practical Electronics | August | 2022