The main control board is designed based on ESP32, with peripheral circuits integrated with DAC, MicroSD, and TFTLCD drivers.

The firmware of this project is based onESP-Arduino development, calling the API of ESP-IDF FreeRTOS, effectively synchronizing the operation of multiple peripherals.

The main program flow is shown in the figure below.

Below are answers to four common questions + three precautions:

1. How to manage so many peripherals?

Three peripherals (considering the LCD display and touch as one) need to run continuously!

In the initial design, two SPI lines were used to control all peripherals, resulting in poor performance. The SPI time-sharing multiplexing tasks can easily run away, and the blocking and notifications of RTOS cannot perfectly stabilize them, limiting the projection frame rate, ultimately choosing to use SDMMC to read the MicroSD card.

2. How to solve the notification and blocking between cache and projection tasks?

The idea is that all upper-level logic only controls the cache, not directly affecting the projection; when the cache is full, it self-blocks; after the projection is executed, it notifies the cache, and the projection depends on the cache, preventing empty frames from occurring during projection.

3. What is the idea of clearing animation data?

When it is necessary to clear the laser animation data in RAM, such as the Clear in DrawNow mode, the idea is similar to stack operations, only adjusting the pointer back to the starting point in memory, clearing variables such as total frame count without actively clearing animation data.

The LCD UI is designed based on SquareLine Studio.

4. What if the LVGL library cannot call my own functions?

In the LVGL library exported by SquareLine, it cannot call my own functions. To use the key callback in lv_events.c, the current method is to define a variable as the key state in this file, declare this variable as an external variable in my own header file, and then judge this variable in the LCD Task, so that key events can be written in my own function file.

5. Compilation, burning, and startup steps

The chip needs at least 2MB of Flash, and when compiling in platformio, you need to add a partition table, which can refer to the official partition table example.The partition table for this project is in the open-source Firmware/esp32/huge_app.csv.

The DAT0 pin of the MicroSD is connected to IO2 of the ESP32, which will force it high. During firmware burning, you need to insert a jumper cap on the H31 pin header to pull this pin low,allowing the ESP32 to enter download mode.

In X-Laser, we chose the N8R8 module chip, which actually does not require so much RAM becausedynamic read and write is used.

The ESP32’s power-on self-start requires the BOOT to be pulled high. Although the BOOT is pulled up by default, it was found in the final version of the design that if it is not manually pulled up, the program will not self-start. Therefore, in the final version of the circuit, a 1K resistor was used for manual pull-up.

In the MicroSD card,create a folder named ILDA and place the laser animation files. After starting, you can see the laser animation files read in the screen roller.

The animation file name length must be less than 15 characters, otherwise, it will not display completely and cannot be played normally.

6. About DrawNow mode

The touch screen refresh and reading touch points have frequency limitations, so “slowly” drawing yields better results.

When drawing laser animations, the laser diode needs to be turned off between two consecutive curves, waiting for the galvanometer to shift before turning back on,otherwise, it will close the entire pattern.

In the ILDA file, these areas have been considered and path planning has been done.

In DrawNow mode, turning off the laser diode and waiting for the galvanometer to shift before turning it back on still has a visual persistence effect. Adding a small delay improves this, with 5ms being the best in tests.Excessive delay may cause animation flickering.

……
else
{
    digitalWrite(PIN_NUM_LASER_R, HIGH);
    digitalWrite(PIN_NUM_LASER_G, HIGH);
    digitalWrite(PIN_NUM_LASER_B, HIGH);
    delay(5); // Ensure curve disconnection
}

// DAC output refresh
digitalWrite(PIN_NUM_LDAC, LOW);
digitalWrite(PIN_NUM_LDAC, HIGH);

7. What is included in the Firmware?

The Firmware includes the firmware source code for the main control board, and the esp32/build folder contains precompiled firmware that can be directly burned. Refer to 【Chapter 6】 for guidance to the open-source website.

The main content of the source code is as follows: