Last modified: 22.3.2025
Started: 29.9.2023
A smart pet feeder with scheduling, remote management, and an LCD display.
The project is hosted on GitLab under the repository food-dispenser. For development details, see the development document.
The project is transitioning from an ESP32 microcontroller to an ESP32-S3-DevKitC-1-N8R2 or N8R8. The N8 variant, with its 3.3V SPI voltage, was selected to streamline PCB design. The original ESP32 implementation encountered memory constraints, hindering the implementation of all intended features. The ESP32-S3's enhanced memory and processing capabilities should enable the full feature set.
Initial wiring and software development. Integration and testing of display, portioning mechanism, and load cell.
Custom PCB designed for the ESP32. Power LED confirmed functional, but no components installed yet. Transitioning to ESP32-S3 requires PCB modification.
Testing communication between software and physical components. Verifying motor, sensor, and display functionality. Load cell readings still require tuning.
Purpose: Test if I can get a display and touch working on the ESP32-S3 because the ESP32-S3 has a lot more memory than the ESP32. This was pretty hard to get working. The library always crashed on init() and it took me a while to figure out what was wrong.
Using a 4.0 inch 480*320px SPI Module ST7796 with an ESP32-S3-DevKitC-1-N8R2.
To be able to use the Display with 3.3V I needed to short J1 on the board, circumventing the 5V voltage regulator on the display.
In order to be able to chain more devices to the SPI bus this display uses to show Graphics and detect touch events I needed to remove a diode marked D1 from the display and short the remaining connections. See TFT_eSPI issue 898
I wired the display to the ESP32-S3 like this:
| ESP32-S3 Pin | TFT Connection | Touch Connection |
|---|---|---|
| 3 | - | T_IRQ |
| 12 | TFT MISO | T_DO |
| 6 | TFT MOSI | T_DIN |
| 10 | - | T_CS |
| 5 | TFT SCLK | T_CLK |
| 7 | TFT RST | - |
| 8 | TFT DC | - |
| 15 | TFT CS | - |
I do not use the User_Setup.h file to define pins for the display, instead I use the platformio.ini which I think is a much clear and better way to define all important project Settings which allows us for example to have all pin definitions in one place.
// Coming soon
I consider this test as a Success because using the TFT_eSPI library examples the I was able to show something on the display and detect touch events.
Purpose: Test if I can put more devices on the SPI bus, the test will be adding an SD-card using the same display and same controller as in the previous test
I wired the display to the ESP32-S3 like this:
| ESP32-S3 Pin | ST7796 Display Connection | XPT2046 Touch Connection | SD Card (SPI) | Function |
|---|---|---|---|---|
| GPIO 3 | - | T_IRQ | - | Touch Interrupt Request |
| GPIO 12 | TFT MISO | T_DO | SD_MISO | SPI MISO |
| GPIO 6 | TFT MOSI | T_DIN | SD_MOSI | SPI MOSI |
| GPIO 10 | - | T_CS | - | Touch Chip Select |
| GPIO 5 | - | - | SD_CS | SD Card Chip Select(SPI) |
| GPIO 7 | TFT RST | - | - | Reset |
| GPIO 8 | TFT DC | - | - | Data/Command Select |
| GPIO 15 | TFT CS | - | - | Display Chip Select |
| GPIO 4 | TFT SCLK | T_CLK | SD_SCK | SPI SCLK |
| 3.3V | VCC | VCC | VCC | Power Supply |
| GND | GND | GND | GND | Ground |
Added the following capacitors to the circuit to stop SD-card failure:
I put the definitions for all pins in the platformio.ini including SD-card pins.
// Coming soon
And some code using the display, touch and reading files from SD-card
// Coming soon
Some Serial output from the device after running the code and pressing the screen a few times
// Coming soon
I am not sure about the result, could be a possible success, because I was able to read from the sd card, display images on the display and detect touch events. But sometimes mounting the sd-card failed, possibly because of the loose wiring and bad connections in the bread-board.
SD-card failure has stopped, the result is a success. I added 0.1µF and 10µF capacitor between the TFT VCC and GND pins close to the display. I added also 0.1µF and 1000µF capacitors between the 3V3 and GND close to the MCU.
Purpose: Learn how to create basic display pages using the LVGL library with the ESP32-S3 and ST7796 display.
This test includes two parts: displaying content on the screen, and displaying content with touch detection. I will demonstrate this with two main.cpp files: main-display.cpp for basic display output, and main-touch.cpp for display output with touch input handling.
Both main-*.cpp files use the same configuration files: platformio.ini and include/lv_conf.h.
Same as in the above example, I put the definitions for all pins in the platformio.ini and the wiring is the same.
The shared files
// Coming soon
// Coming soon
Displaying a label from the LVGL library
// Coming soon
Serial output from the main-display.cpp code
// Coming soon
Displaying a button and detecting touch event when button is clicked using the LVGL library
// Coming soon
// Coming soon
Serial output from the main-display.cpp code
// Coming soon
The result is a success. I was able to display something on the ST7796 display and detect touch using the LVGL library