The E-Ink Paper Display (EPD) on the M5Paper consumes power even when the screen is idle due to its underlying technology. E-Ink displays are different from traditional LCD or OLED screens in that they only consume power when the content on the screen is changed. Once an image or text is displayed on an E-Ink screen, it doesn't require any power to maintain that state. However, changing the content on the screen, such as refreshing to display a new image or text, does consume power.

In your case, when the EPD power is disabled, the display is essentially turned off, and it consumes very little to no power because it's not actively refreshing the content. When you enable the EPD power and the display is idle, it's likely in a state where it's ready to receive new content and is therefore consuming some power in anticipation of a refresh.

The power consumption you're observing is not necessarily a sign of a defective unit but rather a characteristic of E-Ink displays. If you want to optimize power consumption further for your low-power application, you might consider:

Reducing Refresh Rate: Minimize the frequency of screen refreshes. E-Ink displays are typically used in applications where the content doesn't change frequently. You can adjust the refresh rate to be as infrequent as possible to save power.

Full Screen Updates: Instead of partial screen updates, use full screen updates when you need to change the content. Partial updates can be more power-intensive.

Deep Sleep: Continue using the deep sleep mode of the ESP32 when the screen is idle. This will significantly reduce overall power consumption.

Optimize Code: Make sure your code is efficiently managing the display and other peripherals. Ensure that you are properly putting the ESP32 into deep sleep mode when it's not actively needed.

Hardware Modifications: Depending on your specific use case, you might consider hardware modifications to further reduce power consumption. This could involve custom power management circuitry or using different power supplies.

The power consumption you're observing on your M5Paper when the EPD (Electrophoretic Display) is idle is indeed higher than expected. It's unlikely that you have a defective unit, as the behavior you described is more likely related to software or driver optimization.

EPD displays typically have low power consumption because they require power only during screen updates. Once the image is displayed, the EPD consumes very little power to maintain the image. However, it's possible that the EPD driver or the default app on your M5Paper is not optimized for low power consumption during idle periods.

To optimize the EPD power consumption during idle periods, you could try the following steps:

Check for firmware updates: Ensure that you have the latest firmware version for your M5Paper. Manufacturers often release firmware updates that include optimizations and bug fixes that can improve power efficiency.

Look for power-saving options: Check if there are any power-saving options available in the EPD driver or the default app settings. Some devices offer options to reduce the refresh rate or enable power-saving modes for the EPD.

Consider customizing the EPD driver: If you have experience with programming and access to the EPD driver source code, you can explore the possibility of customizing the driver to optimize power consumption during idle periods. This might involve tweaking the refresh mechanism or implementing additional power-saving features.

It's worth noting that while EPD displays are generally power-efficient, power consumption can vary depending on factors like display size, color depth, and the specific implementation of the EPD driver. Therefore, it's not uncommon to encounter variations in power consumption between different devices or even different firmware versions.

I'd be happy to help you with this issue!

Firstly, it's great that you were able to achieve an average of 24FPS on the LVGL music demo. That's a significant improvement and a good indication that your M5Stack Core2 hardware is capable of handling the display requirements.

Regarding the TFT_eSPI library, it's true that the built-in library in the M5Core2 library is outdated and doesn't support DMA. However, the newer versions of the library do support DMA and can provide significant performance improvements.

To use the newer TFT_eSPI library with your M5Stack Core2, you need to follow the installation and configuration instructions provided by the library's developer. Here's a general outline of the steps you need to take:

Download the latest version of the TFT_eSPI library from the library's GitHub repository: https://github.com/Bodmer/TFT_eSPI

Install the library in your Arduino IDE using the "Library Manager" option in the "Sketch" menu.

Open the "User_Setup.h" file in the TFT_eSPI library's "User_Setups" directory and modify the settings to match your M5Stack Core2 hardware. Specifically, you need to configure the display type, pins used for communication, and other settings as required by your hardware. Refer to the documentation and examples provided by the library to make these changes correctly.

Once you have configured the library, you can use the library's APIs to draw graphics and text on the display. Be sure to use the DMA-enabled APIs for maximum performance.

If you encounter any issues during this process, feel free to ask for further help. Good luck!

Regarding the RFID module, the Grove connector on the M5Stack provides serial communication, which means you can use either a SoftwareSerial or the hardware serial to communicate with the module. The SLA and SPI interfaces are different types of communication protocols, so they are not relevant in this case.

To use the hardware serial on the M5Stack, you can simply use the standard Serial library in your Arduino code instead of the SoftwareSerial library. The hardware serial on the M5Stack is available on pins 1 (TX) and 3 (RX) of the Grove connector, so you need to connect the RFID module's TX pin to the M5Stack's RX pin and vice versa.

Here's an example code to get you started with using the hardware serial on the M5Stack:
#include <M5Stack.h>

void setup() {
M5.begin();
Serial.begin(9600);
}

void loop() {
if (Serial.available() > 0) {
// read data from serial and process it
// ...
}
}

In this example, we initialize the M5Stack library and then start the hardware serial communication with a baud rate of 9600. In the loop() function, we check if there is any data available on the serial port, and if there is, we can read it and process it accordingly.

I hope this helps! Let me know if you have any more questions.