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Final part of our quality Weather Station based on System designed by Armindo Caneira* Built and written by Trevor Robinson *www.meteocercal.info The Wireless Display Unit In the last part, we built the RX unit and configured Cumulus to collect, record and display your weather data. Now we are going to complete the Weather Station by building the handy little Wireless Display unit (WDU). T he Wireless Display unit actually evolved from the RX unit (which, incidentally, can also be used as a WDU with some minor mods). It receives wireless data on a 433MHz link from the RX unit (see part 3), which in turn has received data from the outside weather sensors via the TX unit (see part 2). It also sends data from its own DHT22 temperature and humidity sensor. The main differences between the two is the barometer sensor and the run/program pullup switching has been omitted. And of course, it has its own firmware file. Beside having a display screen, it only has one push-button switch (the Display Mode switch) and a LED. The LED blinks when data is received over the 433MHz link. The WDU is powered through its Mini-B USB connector, so you will need a 5V DC power pack with a mini-B USB connetor or a Mini-B USB cable to connect it to a suitable power supply like a USB phone charger. Once again, like the RX unit, you have the option of one of the following five different displays: TFT – ILI9341 2.4” or 2.2” (320x240) or the ST7735 1.8” (160x128) Alphanumeric LCD: 20x4, or 16x2 with I2C module Constructing the Wireless Display Unit The WDU PCB purchased from Meteocercal will al- A completed WD unit with a 2.4” TFT display siliconchip.com.au June 2015  81 (Above): reverse side of the WD PCB; the “top” side at right has the Arduino Nano and 433MHz modules fitted. ready have the surface mount components soldered on, as shown above (there is also an SMD on the opposite side). These can be a bit tricky without the correct tools. Once again, like all electronic kitset projects, it’s easiest to install and solder in the smallest components first: the resistors and capacitors. Next install the LED, observing the polarity, followed by the header and antenna connectors. Like last month, it’s best to install the Nano using a suitable socket. But if you are soldering the Nano directly to the PCB, it’s good practice (as with all heat sensitive components) to stagger the soldering of the pins to help avoid localisation of heat build up. Finally install the BX-RM06 ASK OOK RF receiver module vertically on the WDU board. Ensure that the component side of this board goes to the outside of the WDU board pin – its easy to install this component back-to-front if care isn’t taken. Not only will it not work, it will quite likely be damaged (and it’s a pain to desolder!). The WDU board is now complete but before moving on, double check your work, looking for solder bridges (especially between module and header pins) and cold solder joints. A jeweller’s loupe or magnifying lamp are great tools for getting a good close-up view. the Dupont female to female wires to make life easy. The backlight jumper needs to remain in place, but you may need to tweak the contrast potentiometer. LCD Connecting the display screen Both of these are dependent on what sort of case you get. The momentary action pushbutton switch should be connected by soldering wire to the contacts and then the other end to the contacts of the header connector plug. The LED can be soldered into its position on the PCB, though it would be better to use a suitable length of cable to connect it to the PCB from somewhere visible on the case. The push button changes the display mode as per the table below: Much of the following information is repeated from last month’s (Part 3 – The Receiver) issue because the Wireless Display Unit and Receiver Unit share a common heritage and indeed, most parts TFT pin assignment are interchangeable. TFT display Use nine of the Dupont female to female wires to connect PCB pin headers to TFT pin headers. Currently the SD card and touch overlay are unused. Alphanumeric LCD PCB TFT Display 2.4” TFT – ILI9341 320x240 SCLK SCLK MOSI SDA CS CS RST RESET SDI(MOSI) PCB LCD GND GND This is the same as what we did for 5V the RX unit. We’ll cover it briefly again, 5V just in case your dog ate your homework SDA SDA last article. Solder four header contact pins to SCL SCL one end of whatever length of cable you DHT22 Temp. Sensor require. The maxiPCB Schematic Pin DHT 22 pins mum length this cable can be is five metres. GND 1 (GND) 3 OR 4 Solder and heatshrink 2 (D6) 2 the other end to the DAT four legs of the DHT22 5V 3 (5V) 1 sensor. Ensure the pin assignment matches the table above. Push button (display mode switch) and LED (data received indicator) SCK Display Mode Switching LCD TFT CS Short press Nothing Toggles the Display off/on RESET Long press Nothing Toggles the big font size screen DC A0 D/C 5V VCC VCC GND GND GND The LCD connection LED process is simpler as it LED+ LED+ only uses four wires. LED- LED- No connection You can also use four of needed 82  Silicon Chip Connecting the DHT22 temperature sensor Pinouts Button Action Double press     Toggles the information screen The information screen shows the firmware version, TX unit voltage and case temp from the TMP36 sensor. Programming the WeatherDuino Pro2 Nano Since you are now an old hand at programming Arduinos, we shouldn’t have to go into too much detail here. If you siliconchip.com.au Another view of the completed WDU PCB, this time showing the method of mounting the 433MHz wireless link. Take care with this – with four pins at each end it’s not difficult to solder it in the wrong way . . . but rather more difficult to unsolder it and fix your mistake! need a refresher, part two had an in-depth guide to setting up the IDE and part three covered reading and altering of the WeatherDuino code to suit that application; maybe read those again. Acquire the required firmware Download the required firmware file from here: www. meteocercal.info/forum/Thread-WeatherDuino-Pro2-WDSoftware-Latest-Release Save the file to wherever, then extract the contents into your Arduino sketch folder which should be in the \users\ your_username\Documents\Arduino folder. Click “OK” on any merge or overwrite dialog boxes. Now go into that folder and double click the folder WeatherDuino_WD_vxxx_bxxx (the “x”s change by release version). Then in that folder there should be a file called WeatherDuino_WD_vxxx_bxxx.ino – double click that to open it in the Arduino IDE. Configuring the code Now we need to tweak a few lines to suit our WDU setup. Scroll down to around line 44. We need to start by changing the code to suit our display type, so pick your display type number from the comment section: 0= TFT 160x128 ST7735, 1= TFT 320x240 ILI9341, 4= 20x4 LCD, 5= 16x2 LCD Say your have the big LCD display, you would change the line to read this: #define DisplayType 4 // 0= TFT 160x128 ST7735, 1= TFT 320x240 ILI9341, 4= 20x4 LCD, 5= 16x2 LCD The big TFT display is set to the default so you would just leave that line as is. Next is the Backlight timeout: byte BackLight_Timeout = 0; // Timeout for TFT backlight in minutes (1 to 255). 0= Always ON siliconchip.com.au You have the option of having it on continuously (though a short button press turns it off) or setting the timer to turn it off automatically some time after the last button press. Your choice. If you want to just manually turn off the backlight then just leave the default setting. Next is the Temperature sensor type. Since we when with the good old DHT22 you can left this line alone also. The next line you also leave at the default setting of 1 #define Board_Type 1 // 0= Standard Boards, 1= Extended version Wireless Display Boards Pretty simple configuration on this unit isn’t it? Save it with a filename that reflects your setup so if you wish to tweak/change it in the future, you will know what it is. Compile and upload it to the Nano by pressing the right arrow in the Arduino IDE. After a short period of time the WeatherDuino Pro2 Wireless Display unit should reboot and a little while later the inside temperature should be displayed and after a little more time the outside data should display. If the IDE produces errors its usually one of two things: 1: File too big. Your are not running the Arduino IDE version 1.5.8 or greater. 2: The library files are not where the IDE is expecting them. Double check they are in the sketch folder or manually import them in the IDE (Sketch/Import Library). That’s all folks! We hope you enjoyed creating this project and find the data this weather station creates is more reliable and accurate than your previous station may have produced, or even the weatherman on the radio. We certainly did! When you get you weather station online, please leave a post on the Meteocercal forum so you can have your station added to the WeatherDuino user map here: www.meteocercal.info/forum/misc.php?page= WeatherDuino_Users_Map SC June 2015  83