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Mini Projects #025 – by Tim Blythman SILICON CHIP Weather Monitor Our WiFi Weather Logger Mini Project from last December has been handy for keeping track of temperature and humidity. However, it isn’t always convenient to use a computer to check on its status. This Mini Project that makes it easy to monitor the Logger’s temperature and humidity without needing to open up a web browser. T he WiFi Weather Logger Mini Project (December 2024; siliconchip. au/Article/17315) is a compact unit consisting of a WiFi Mini processor module, a DHT11 temperature and humidity sensor and board that interfaces to a microSD card. It monitors the temperature and humidity by reading the sensor and makes that data available as a web page via WiFi. It also records the data to the card, and that data can be downloaded as a simple yet flexible CSV (comma separated variable) file. CSV files can be opened by many spreadsheet programs, so it is easy to analyse the data and create charts and the like. We often found ourselves using the interface to simply check the temperature and humidity. That means opening up the web page on a computer or smartphone screen and viewing the data. It is not difficult, but we realised that it would not take much hardware to create a simple, standalone monitor. The result is this Weather Monitor. It consists of an Arduino Uno R4 WiFi board attached to a liquid crystal display (LCD) shield to provide a clear and simple readout of the current temperature and humidity. Since the Weather Logger keeps track of time, the Weather Monitor can also display that time. Handily, Hardware The hardware is little more than an Uno R4 WiFi with an XC4630 Colour LCD Shield plugged into it. You’ll also need a suitable USB-C cable to power the Monitor, since the Uno R4 WiFi has a USB-C socket. Screen 2: you need to edit the WiFi network security settings (SSID and password) and set the IP address of the Logger so that the Monitor can communicate with it. You can also change the colour scheme at the same time. Screen 1: the WiFi Weather Logger serves up a web page that looks like this. By looking for key character sequences, the Monitor can extract the information to reformat it for its screen. siliconchip.com.au the Monitor also displays the status of the Logger, so you can quickly see if it is having problems, such as an SD card problem or lost WiFi connection. The Uno R4 WiFi is much more powerful than the older R3 Uno, so this simple combination of hardware could have many other handy uses, as a simple internet-connected display device. Australia's electronics magazine April 2025  45 The LCD Shield just plugs into the headers for the Uno R4 WiFi. The stack is around 20mm deep, and the two boards are about the same width. Thus, the assembled stack will rest neatly on its edge, as you can see in our photo. The orientation we have chosen allows the USB cable to attach near the Monitor’s lower edge (on the righthand side), meaning the cable does not hang awkwardly. This can be changed if you like. Software Web pages are requested and received using the hypertext transfer protocol (HTTP). The WiFi Weather Logger works as an HTTP server, offering web pages via its WiFi interface. Thus, the Weather Monitor needs to use an HTTP client to access those web pages. Interestingly, it’s a lot easier to write an HTTP server program than an HTTP client with the Arduino IDE. That’s because there are Arduino libraries for creating HTTP servers, included with most WiFi-capable board profiles. So implementing an HTTP server is easy to do with the Arduino IDE. Downloadable HTTP client libraries exist, but a client must handle all the possible server options, while a server gets to choose which options it offers. Also, a client may have to deal with a large amount of data if the server delivers a large file. Because of this complexity, our Monitor software has been specifically written to handle the server protocols used by the Logger. It should work fine if you want to customise the software to work with other Arduino HTTP servers, but it may not work with other server types. The software connects to a pre-­ programmed WiFi network and attempts to download the web page from the Logger using its IP address. This means you should ideally set your router to allocate the Logger a fixed IP address. This might be called something like address reservation in your router settings. Otherwise, you might find your router allocates a different IP address to the Logger at some point and the Monitor can’t find it. This could happen if, say, the power goes off, or the router is reset. The Logger and Monitor must be on the same network, such as the same home WiFi network. There are ways to make the Logger accessible from the wider internet, but these are well beyond the scope of this article as they require a good knowledge of network security principles. When the Monitor downloads the web page, it scans the contents for key sequences to locate necessary information. For example, once it finds the text “Temp: ”, it knows that the temperature reported by the Logger will follow. Screen 1 shows a typical page served up by the Logger. The web page is a HTML (hypertext markup language) document that Parts List – Weather Monitor (JMP025) 1 assembled WiFi Weather Logger (see our December 2024 issue) 1 Arduino R4 Uno WiFi main board [Jaycar XC9211] 1 2.5in colour LCD shield [Jaycar XC4630] 1 USB-C cable to suit the Arduino Uno R4 WiFi [Jaycar WC7900] Screen 3: the Serial Monitor output should look like this for a normal startup. We found that our unit took up to 20 seconds to connect to a WiFi network (when it waits to receive the IP address), plus another five seconds to access the web page. contains so-called tags that are not visible in a web browser, although they change how the web page is rendered on the screen. For example, the title is extracted by looking for the “<title>” tag. Apart from the raw information on the page, the Monitor also records a timestamp (using its internal milliseconds counter) of when the web page was retrieved. From that information, it can show an updating time display without having to continually load data from the Logger. The Monitor tries to load a page from the Logger every minute, and updates its displayed information when it does so; the time and date display is updated continuously. If there have been no successful updates for an hour, the screen reports this instead of repeating stale data. Assembly for this project is literally plug and play! The shield simply plugs into the main board and then it is ready for programming. 46 Silicon Chip Australia's electronics magazine siliconchip.com.au Screen 4: while starting up, you will see a screen like this on the LCD. It also might appear if the Logger is offline and the Monitor can’t communicate with it. While the display shield has a touch sensor, we do not use it. It’s easy enough to display all the available information, so there are no selections that need to be made. The WiFi interface is also blocking, meaning that whenever it is busy, we wouldn’t be able to check for a touch input anyway. Uno R4 board profile Assuming you have completed construction by plugging the LCD shield into the Uno R4 WiFi board, you can start the programming process. You will need the Arduino IDE with the Uno R4 Boards profile installed. The sketch itself includes some library files, but there are no external libraries needed. The Arduino IDE can be downloaded from www.arduino.cc/ en/software To install the Uno R4 Board profile, open the Boards Manager, search for “R4” and install the “Arduino Uno R4 Boards by Arduino” option. We used version 1.3.2; other versions should work fine, but if you have problems with the sketch compiling, try changing to this version. Programming There are some customisations that you will need to apply to the sketch before uploading it. Open the WEATHER_LOGGER_MONITOR sketch and switch to the WEATHER_ LOGGER_MONITOR.ino tab, as shown in Screen 2. Lines 2, 3 and 4 contain the WiFi network settings and IP address of the Weather Logger (which you should have built previously). Change these siliconchip.com.au Screen 5: if you see this screen then all is well. The remote temperature, humidity and time are reported; the time is kept current using an internal timer on the Uno R4 WiFi. to suit your network and the Weather Logger that is connected to it. You can set the display’s colour scheme on lines 14 and 15. FGC is the foreground (text) colour, while BGC is the background. BLACK, WHITE, RED, BLUE, GREEN, CYAN, MAGENTA, YELLOW and GREY are available #defines that are set in the XC4630d.c file; you can also use 16-bit RRRRRGGGGGGBBBBB format colour values. Lines 8-11 of the XC4630d.c file also set the version of the XC4630 LCD shield; the most recent V4 is enabled (by not being commented out with “//”). If you find this version does not work, you can try the other versions. You can flip the orientation of the display by changing the command XC4630_rotate(4) to XC4630_rotate(2) in the setup() function. After these changes, the sketch is ready to upload. Make sure to choose the Uno R4 WiFi board and its correct serial port (eg, COM port on Windows). Open the serial monitor to 115,200 baud and be ready to view the startup messages as seen in Screen 3. If the Monitor does not connect to the WiFi network within 30 seconds, it will reset itself to try again. We found that even with the correct settings, the Monitor sometimes failed to access the Logger’s web page. You can either wait 60 seconds for it to try again or use the reset button on the Uno R4 WiFi. The LCD should show information similar to that in Screens 4 & 5, depending on its phase of operation. The software can be downloaded from siliconchip.au/Shop/6/1836 Australia's electronics magazine You can see a video of the Weather Monitor booting up and then displaying the weather & time at siliconchip. au/Videos/Weather+Monitor Summary If you see something like Screen 5, then everything is working as expected. The status line at the bottom of the page will report when the Monitor is trying to download fresh data, while the clock may occasionally stall for a few seconds due to the blocking nature of the WiFi interface. We considered adding charts to the Monitor by having it download the CSV files from the Logger, but the amount of RAM on the Uno R4 WiFi is not enough to allow this. If you are a dab hand with Arduino, you might like to try customising the Logger or Monitor sketches to report different data. Changing the title of the Logger’s web page, for example, should change the title displayed on SC the Monitor. This Weather Monitor uses a wireless connection to our previous WiFi Weather Logger to collect data. The Logger is built using just an ESP8266, DHT11 and microSD card shields. April 2025  47