WTF?

This is a wall clock based on the Elecrow display-7.0 Inch HMI Display 800x400 RGB TFT LCD Screen Compatible with Arduino/LVGL/PlatformIO/Micropython. For more information about this device, see its Wiki

This device is a wall clock that will eventually display Internet accurate time of day, day of week, date, local weather, and automagically adjust for daylight savings time (if it survives 2024 as a concept -- it seems there are many people like me who think it's a bogus concept and should be eliminated -- one can only hope).

I built this because I bought an "atomic" (WWVB in the USA) calibrated wall clock which is very nice, but it could never hear WWVB -- I assume this is because my home lab is rather electrically noisy. But I wanted a wall clock so I wouldn't have to fumble with my mouse or reserve desktop screen real estate to know the time of day and date or weather at a glance.

I built this using ESP-IDF from Espressif, a Shanghai company whose products I have come to admire in recent years. This device uses the ESP32-S3, which as I developed this is one of the newer forms of ESP32 SoC, including a LCD panel driving module in the SoC that drives the LCD on this board.

I found Arduino stuff to be too version-drifty and too badly documented.

I found LVGL to be well documented, but integrating with Arduino could be challenging because, again, version-driftiness.

So I use LVGL 8.3 (as of this writing) integrated with ESP32 using ESP-IDF. The LVGL software was added simply by adding LVGL as a dependency in my project (see idf_component.yml for details). The ESP-IDF build system pulled in the specified version of LVGL and built it with no fuss.

I used LVGL 8.* because version 9.* isn't quite baked yet and the APIs changed a good bit for integrating a display driver. What can I say? I'm lazy.

Building

First, install the excellent ESP-IDF from Espressif. I used that version for that SoC chip because that is what matched the board's SoC and it is the most recent stable release as of this writing.

Connect the board to a USB port on your computer that can source several amps. I used a USB3 (blue) USB port on my rather hefty desktop machine and it worked fine. The display should boot up and run its factory sample software when you do this. For me, on my Linux box, this device showed up as /dev/ttyUSB0 because I make it a rule to remove other serial devices when I'm just fooling around with a new toy, so I didn't have any other devices to contend with.

You have to do something manual to get into the "download mode" of the board. Just press and hold the RESET button, press and hold the BOOT button, release the RESET button, release the BOOT button. This becomes second nature after doing it a few thousand times. This puts the board into "download mode" which allows the ESP-IDF software to flash a new build.

If you want to reset the board and run what is in its flash, just click the RESET button.

You can run the ESP-IDF monitor to see the terminal output of the board when it boots. For the factory demo software I remember this as being pretty boring, but it will show you if you're connected properly.

When you have cloned this git repository, you can just go to its top level directory and do

. ../esp-idf/export.sh
idf.py -p /dev/ttyUSB0 build flash monitor

When the build is complete, ESP-IDF will start to flash the new image, which takes a few seconds. While that is going on, the monitor mode is running, so you can see its progress. If the board wasn't in "download mode" when you ran this command you can just do the RESET-BOOT sequence described above to get it into that mode and run the command again. The second time, since no changes were made, the build flash monitor doesn't have to rebuild anything and it will flash the image immediately.

When the flashing process is done the monitor will show a message like Hard resetting via RTS pin... but this board isn't designed to reset when the USB serial interface's RTS pin is wiggled, so you have to press the RESET button manually. This will start your new flashed image.

To exit the monitor mode you can just hit control-]. The board will continue to run its software even if you're not watching it, like a good little computer.

TO DO

• Set backlight using PWM instead of always full ON.

• Vary backlight based on room occupancy and light intensity and via Home Assistant MQTT messaging or similar.

• Build the clock UI to replace the toy scatterchart UI.

• Optimize display updating to avoid full copy of the framebuffer each time? Scatterchart gets ~16FPS with double buffering. While this is surely enough for a wall clock, it somehow seems inelegant to leave this poor little machine working so hard to accomplish so little.

UI and Functional Notes

• In normal operation, Wallclock shows the time, day and date, a Settings icon button, and a status bar.

• Clicking the Settings button brings up the settings UI:

  • List of WiFi APs known to Wallclock and a UI to change or delete any of these.
  • A button to add more WiFi APs by scanning for them and entering credentials and an NTP pool hostname list.

• Wallclock saves in its internal flash storage an encrypted set of WiFi credentials for some number of WiFi APs it can associate with.

• If WiFi doesn't find any authenticatable, functioning, and NTP reachable WiFi access points it knows about, the status bar will show Internet Down or Network Time Protocol Down status.

See this link for the UI design wireframe I made with the unfortunately somewhat crippled free version of the wonderful tool LucidChart. Each "slide" in the LucidChart is framed as a slide solely so I could see what the UI would look like in a frame. LucidChart can do way more than slide presentations! Note: I have no affiliation with the Lucid.app people other than using and liking their tools.

In that drawing, the green lines show the objects I use for alignment and grouping. These are invisible in the UI, but they do allow groups to be aligned as a unit and to layout the contents of the group according to the Flex Flow rule provided by LVGL.