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Make it with Micromite Phil Boyce – hands on with the mighty PIC-powered, BASIC microcontroller Part 39: Using infrared to synchronise time L ast month, we showed how easy it is to set up a PicoMite BackPack. We focussed on the 2.8-inch 320x240 touch TFT module, as this has the same-sized screen which was used in the original Micromite BackPack (and thus in many PE projects). In addition, we showed how to use the bigger 3.5-inch touch TFT with a higher resolution of 480x320. However, we also mentioned that there are many smaller (and cheaper) screens that can be used, which are handy if you only want to show a small amount of data, for example, the time. Since last month, we have received numerous emails about using these smaller screens; in particular, asking for help with the OPTION settings. Therefore, we will begin this month with a useful guide covering some of the more popular smaller screens. While setting up the hardware for this task, I simply connected a PicoMite to a display, wrote a short program to show the time, and left the unit on test while setting up the next PicoMite. Fortunately, I had recently received a delivery of new RPi Pico modules and display modules; so I was able to set up multiple ‘clocks’ and position them side by side. Note that no RTC (real-time clock) was used in any of these clocks. Instead, each clock was configured using just MMBASIC’s built-in TIME$ variable. All I did was set TIME$ at the command prompt to a value as close to the exact time as possible. Everything was going well, but then my 10-year-old son made a comment; he noticed that the clocks were all showing a slightly different time and asked, ‘which clock is actually correct?’. I gave the ‘time is relative’ answer, and then went on to tell him that probably none of the clocks were showing exactly the correct time. However, it gave me an idea for a topic that I had planned for a future article – infrared (IR) communication. So, the second part of this month’s article will demonstrate how to synchronise several clocks to show the same time by using MMBASIC’s built-in IR SEND command. Essentially, we will show you how to add an IR transmitter to one clock (the ‘master clock’), and then add an IR receiver to each of the other clocks so that they can all be set to show the same time. For this article you will need at least two PicoMite BackPacks (ideally three or more), but do remember that a PicoMite costs less than £4, and displays start from only around £5 (and much less from the likes of eBay if you’re prepared to wait Micromite code The code in this article is available for download from the September 2022 page of the PE website. 48 Fig.1. The Waveshare Pico-LCD-0.96 display module makes for a compact PicoMite BackPack. It has a really nice IPS screen with a resolution of 160x80. for delivery from the Far East). The only other parts you will need are probably already in your spare parts draw: an NPN transistor, a couple of resistors, a single IR transmitter LED, and as many IR receivers as you have PicoMite BackPacks. Let’s begin by showing the OPTION settings to create some PicoMite BackPacks with smaller screens. 0.96-inch (160x80) IPS screen This is one of my favourite small screens. It produces a very clear image with vivid colours, and a great viewing angle. It is available from many suppliers as a standalone screen (and is the same screen we used back in MIWM, Part 9, PE, Oct 2019). It is also available as a Pico plug-in module (see Fig.1 from last month – top-left image). If you search online for ‘Waveshare Pico-LCD-0.96’ you will see that this plug-in display module costs around £7. With the display module and PicoMite connected to each other, you will need to enter these two configuration settings at the command prompt: OPTION SYSTEM SPI GP10,GP11,GP28 OPTION LCDPANEL ST7735S,L,GP8,GP12,GP9,GP13 Once these are set, you will find all the usual MMBASIC graphical commands will work with this screen. To test this, try it with something like: CLS RGB(CYAN). If you do not see the screen change to the appropriate colour, type OPTION LIST and check the parameter values are entered as shown above. Any errors will need to be fixed – you do this by first typing OPTION LCDPANEL DISABLE and then either OPTION SYSTEM SPI DISABLE (if you made an error with one of those Practical Electronics | September | 2022 Fig.3. The Waveshare Pico-LCD-1.3 display module running the clock code, as listed in the text. Fig.2. Ensure your OPTIONs are set with these parameter values to make the Pico-LCD-0.96-inch screen operate correctly. Shown here, the program listing for displaying the clock in Fig.1. parameters), or by re-entering the OPTION LCDPANEL setting, this time with the correct parameters. Next, set the TIME$ variable as close as possible to the correct time with the command TIME$=”hh:mm:ss” (replacing hh, mm and ss with the appropriate values). Finally, enter the following five-line program code: BOX 0,0,160,80,5,RGB(green),RGB(blue) DO TEXT 80,40,TIME$,cm,3,1,RGB(yellow),RGB(blue) PAUSE 10 LOOP RUN the above program to see the time displayed in the centre of the screen; the result is shown in Fig.1. It is also worth making the program automatically start up on power-up, so stop the program (Ctrl-C), type OPTION AUTORUN ON at the command prompt, and then RUN the program again. Note that if power is removed, then the TIME$ variable will be reset to ’00:00:00’ at power-up. This is useful because it will better demonstrate the IR time-synchronising that we will cover shortly. Fig.2 is a screen grab of the OPTION settings, and also shows the program listing (with a commented line at the start showing which screen it is). 1.3-inch (240x240) square TFT Another useful Pico plug-in display module is the Waveshare PICO-LCD-1.3 (top-right, Fig.1 in last month’s article). In addition to the 240x240 screen, there are four pushbuttons, and a digital joystick (up, down, left, right and select). The cost of this display module is around £8. To configure this display, enter the following configuration settings at the command prompt: OPTION SYSTEM SPI GP10,GP11,GP28 OPTION LCDPANEL ST7789,L,GP8,GP12,GP9,GP13 The program is identical to the one above except for the differences highlighted in bold. Because these two screens have different pixel resolutions the code Fig.4. A standalone Waveshare 0.91needs to be altered so inch OLED module requires just four that items are displayed connections to the PicoMite – see text in the correct positions for details. (and in a suitably sized font). With the program entered, set OPTION AUTORUN ON and then RUN the program. You will once again see the time displayed in the centre of the screen (see Fig.3), and that completes the second clock. 0.91-inch (128x32) OLED OLED (organic light-emitting diode) displays are made up of individually controlled LEDs, so they don’t need a backlight. Hence images on an OLED are generally superior to those on an LCD. They have high contrast, making them easy to read, even compared to the older-style LCD character modules, such as the 16x2, 20x2 and 40x4 displays. Several Pico plug-in OLED display modules are available, but the current ones are not directly supported by the PicoMite because the relevant display drivers are not built into MMBASIC. However, there is nothing to stop us from using a standalone OLED module that is supported by MMBASIC. For example, if you search for ‘Waveshare 0.91-inch OLED’ you will see a compatible OLED module that costs around £5. Note that this OLED module is not a colour OLED; instead, it is mono (single colour), typically white or blue. This display is easy to interface to a PicoMite since there are just four wires to connect (refer to Fig.4): OLED PicoMite VCC 3V3 GND GND SDA GP0 SCL GP1 To configure this OLED module, enter the following configuration settings at the command prompt: You will notice that the settings are almost identical to the 0.96-inch screen above – the only difference being the display driver parameter: ST7789 instead of ST7735S. This is something I like about the Waveshare display modules; they try to use consistent GP pin numbers for identical pin functions across their range. With the 1.3-inch display configured properly, quickly test it: set TIME$ and enter the following five-line program: As before, set the TIME$, set OPTION AUTORUN ON and enter the following program code: BOX 0,0,240,240,5,RGB(green),RGB(blue) DO TEXT 120,120,TIME$,cm,5,1,RGB(yellow),RGB(blue) PAUSE 10 LOOP CLS DO TEXT 64,16,TIME$,cm,3,1 PAUSE 10 LOOP Practical Electronics | September | 2022 OPTION SYSTEM I2C GP0,GP1 OPTION LCDPANEL SSD1306I2C32,L 49 Once again, the time is displayed in the centre of the screen; or more realistically, due to the lower pixel-count (and appropriate font size), the time essentially fills the entire screen space – see Fig.5. 1.28-inch (240x240) round LCD This screen provides a nice alternative to the usual square/rectangular displays. It is available as a Pico plug-in module – see Fig.1 from last month – top centre image. That one is advertised as an LCD screen; whereas the standalone round display is advertised as being an IPS screen (IPS is generally regarded as giving a much better display Fig.6. The Waveshare 1.28-inch than an LCD). I ordered a standalone IPS display, round LCD standalone module but having seen it in operation, I must question needs eight connections to the Fig.5. The Waveshare 0.91-inch OLED whether it is really is an IPS display because the viewing angles are more like a standard LCD. PicoMite clock – here it is using a white display. PicoMite – see text for details. Anyway, since I received several emails asking about the specific configuration setup for this display we’ll the clocks to show the same time. Depending on how many continue. Bearing in mind I have a standalone display rather PicoMite clocks you have access to, you will need to modify than a Pico plug-in module, I had to first make the following the hardware of one (and only one) of them to act as the connections (refer to Fig.6): master clock by adding a simple IR transmitter (Tx) circuit. The remaining clocks are modified to act as slave clocks by LCD PicoMite adding an IR receiver (Rx) to each one. VCC 3V3 You will also need to make suitable changes to the software. GND GND The master clock program code needs to be able to transmit DIN GP11 it’s time data via the IR Tx; and the slave clock program code CLK GP10 needs to be able to receive this time information (via IR) so CS GP9 that it can update it’s TIME$ variable to the value received. DC GP8 Using this simple concept means that all clocks will display RST GP12 the same time. BL GP13 Master clock The above pins were selected to match the pin-out of the equivalent Pico plug-in display module, so the following should work for either type of round display module. If ypu use a Pico plug-in module, you will notice that once again Waveshare have used consistent GP pin numbers for identical pin functions and hence it is just the display driver reference (GC9A01) that is the main difference from what was used on the previous (non-OLED) screens above. By the way, the typical cost of the standalone display module is around £13, whereas the Pico plug-in module (complete with digital joystick) costs around £23. To configure this display, enter the following configuration settings at the command prompt: OPTION SYSTEM SPI GP10,GP11,GP28 OPTION LCDPANEL GC9A01,L,GP8,GP12,GP9,GP13 After configuring it, quickly test it with something like CLS RGB(red), then set the TIME$, and also set OPTION AUTORUN ON. Last, enter the following program code: The master clock IR transmitter circuit is shown in Fig.8 – it can be connected to any spare GP output pin – in this case it is connected to GP22. The component values used do not need to be exactly the same – the circuit is provided more for guidance, but remember that a Pico output pin has very limited current drive capability, so an IR Tx LED cannot simply be connected to a GP output pin. With this circuit in place, the Pico remains within operational specification limits, and it also means that the Pico can drive the IR Tx at 5V (resulting in better range – not that much range is really required for this application). Now build the IR Tx circuit and connect it to one of your PicoMite clocks. As a reference, we built the circuit on a breadboard, then used three male-female DuPont leads to connect it to the PicoLCD-0.96 PicoMite Clock (that was moved onto an Expander module – see Fig.9). By using this display module for the master clock, we were able to use the bottom right-hand button (referred to as ‘User Key B’) as a trigger to transmit the time data. All that was required to achieve this was the command SETPIN GP17,INTL,btn,PULLUP at the start of the program code, meaning that the program will jump to a subroutine (called btn) whenever the button is pressed. We then put the IR transmitting CLS RGB(blue) DO TEXT 120,120,TIME$,cm,2,2,RGB(yellow),RGB(blue) PAUSE 10 LOOP The program is identical to that above except for the differences highlighted in bold. With everything entered correctly, you will once again see the time displayed in the centre of the round screen (see Fig.7); and that completes the fourth clock. Adding IR We are now going to discuss how to add IR functionality to the clocks so that we can demonstrate how to synchronise 50 Fig.7. The Waveshare 1.28-inch round LCD PicoMite clock. Practical Electronics | September | 2022 VSYS 7 Infrared (IR) L ED 1 GP22 code in this subroutine. Transmitting IR data is made simple thanks to the MMBASIC command IR SEND – please refer to the PicoMite User Manual for more details about the parameters used with this command. Slave clocks Each slave clock just needs a standard TSOP IR receiver connected GND to any spare GP input pin – in this case we will use GP22. Fig.10 shows the connections but note that we Fig.8. This simple IR must connect the TSOP IR Rx to a transmitter circuit uses 3.3V supply rather than the more an NPN transistor, a usual 5V supply. The reason for this couple of resistors, and is that the maximum input voltage an IR Tx LED. on any input pin (here GP22) is 3.6V. So, by supplying 3.3V to the TSOP, we will keep the input voltage on GP22 below the 3.6V limit and not damage the Pico. Connect a TSOP IR receiver to GP22, GND and 3V3, as shown in Fig.10. We used three female-female DuPont leads with the TSOP inserted at one end, and the other end used to connect to a 1.3-inch PicoMite clock (that was moved onto an Expander module – see Fig.11). The program code can then use the standard IR interrupt (set up with the two commands: SETPIN GP22, IR and IR DevCode, KeyCode, myIrInt). This will result in the program code jumping to a subroutine (here called myIrInt) whenever an IR signal is detected. We then put the IR receiving code in this subroutine to process, check, and if necessary, update the TIME$ variable. Software The two required program listings are a bit too long to print line-for-line here, so we have made two downloads available at the September 2022 page of the PE website. Download the MasterClockIR.txt and SlaveClockIR.txt files and load them into the relevant PicoMite clocks. RUN both programs, and if using a PICO-LCD-0.96 as the master clock, press the ‘B’ button to sync and update any slave clock that is within range of the master clock. If you are not using a PICO-LCD-0.96 as the master, you will need to modify the start of the MasterClockIR program to allow for a suitable trigger (see comments within the code for how to do this). Fig.9. A Pico-LCD-0.96 master clock built on an expander module allows easy connection via three DuPont leads to the IR Tx circuit (which here has been assembled on a breadboard). Button B is used to send the time data via IR. that it is actually the Epoch time that is transmitted via IR, and the SlaveClockIR code converts it back into a recognised date/ time. We do this because it means we only need to transmit five 7-bit key code values to transfer both date and time (refer to code comments for more details). I hope this has shown you how easy it is to transmit a few bytes of data between PicoMites. Why not have a think about how you can use IR in your project other than to decode button presses from an IR remote control. If you come up with anything interesting, then do drop us an email and maybe we can mention it in a future article. Next time Next month, we will continue our exploration of the PicoMite and show you how to use a GPS receiver (another low-cost Pico plug-in module) to create a simple and Questions? Please email Phil at: useful tracker. contactus<at>micromite.org Until then, stay safe, and have FUN! Epoch time If you take a closer look at the program code, you may spot two new commands: EPOCH(now) and DATETIME$(n). The first command converts the current date/time into ‘Epoch time’ (a number which represents how many seconds have elapsed since midnight GMT on 1 January 1970). The second command converts an Epoch time value into the usual date/ time format. Why use these? Epoch time makes it much easier to do date/time calculations. For example, to add an hour onto the current time, convert the current IC1 time into Epoch time, add 3600 TSO P 4xx and convert back to normal date/ IR receiver time. This way, we don’t have to worry about roll-over for something GP22 3V3 awkward like 31 December 1999 GND at 23:34:56 (which would mean rolling over date, month and year, as well as the hour to ‘00’) all very Fig.10. The IR receiver tricky when you start looking into comprises just a single it – but very easy with conversion component – a TSOP to an Epoch-time value. IR Rx. Ensure it is Further examination of the connected to the 3.3V MasterClockIR code will reveal supply – not 5V. Practical Electronics | September | 2022 Fig.11. A Pico-LCD-1.3 slave clock built on an expander module allows easy connection to the TSOP IR Rx via three DuPont leads. 51