ESP32 OLED Demo

Source address:GitHub source address

Realize function

The ESP32 OLED demo implements the following functions:

• Temperature and humidity data collection
• Network update real time
• OLED paging display temperature and humidity, real-time time
• Gesture/touch sensor control OLED display page up and down
• Manually enter low power mode via touch sensor

The following picture shows the physical hardware picture of ESP32 OLED Demo:

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Hardware composition

The DEMO uses ESP32_Button_Module_V2 as the development board, and contains the following components:

• Proximity/Ambient Light Sensor (APDS9960)
• OLED display (SSD1306)
• Temperature and humidity sensor (HTS221)
• Two touch sensor buttons

Complete hardware schematic diagram:ESP32_BUTTON_MODULE_V2.pdf

Schematic diagram of display screen and sensor power switch control:

VDD33 is the LDO VOUT 3.3V terminal, used as the power supply for ESP32, peripherals, and flash; VDD33_PeriP is the power supply for the display, temperature and humidity sensors, and gesture sensors. Transistor SI2301 is used as a power switch to control the voltage of VDD33_PeriP. By default, the gate terminal of the transistor is kept high and the power switch is turned off. The power switch is turned on by controlling Power_ON to keep it low.

software design

We used the following methods to implement the ESP32 OLED demo:

• Use esp-iot-solution development kit
• Based on FreeRTOS real-time operating system, multitasking
• SNTP protocol to obtain real-time time
• Enter low power mode through touch sensor
• Wake up the device via touch sensor

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Low power mode description

Low power mode hardware design

We have used the following methods to minimize the power consumption of the device in low-power mode.

• Control the power switch of the display screen, temperature and humidity sensor, gesture sensor
• Choose low-power LDO, quiescent current is about 1 μA
• Power consumption management for touch sensors

Touch sensor duty cycle

When the touch sensor is working, there are two states: sleep and measurement, the two states cycle alternately. In the normal working mode, we set the sleep time to be relatively short. After entering the low power mode, we set the sleep time to be relatively long to reduce power consumption as much as possible.

Called before entering low power modetouch_pad_set_meas_time(uint16_t sleep_cycle, uint16_t meas_cycle) The interface adjusts the sleep and measure time of the touch sensor.

Parameter Description:

• sleep_cycle：sleep_cycle Determines the interval time between two measurements, the interval time t_sleep = sleep_cycle / (RTC_SLOW_CLK frequency).

  can use rtc_clk_slow_freq_get_hz() Interface acquisitionRTC_SLOW_CLK frequency value.

• meas_cycle：meas_cycle Determine the measurement time, the measurement time t_meas = meas_cycle / 8M, the maximum measurement time is 0xffff / 8 M = 8.19 ms.

Low power mode use

Long press the touch sensor button to enter the low-power mode. In the low-power mode, the sampling frequency of the touch sensor will be reduced to the lowest. Therefore, waking up from the low-power mode also requires a little longer to touch the sensor button. The current sampling in low power mode is as follows:

• The current sampling diagram of the LDO VOUT 3.3V terminal in low power consumption mode is as follows (including the current consumed by ESP32, display and sensor):
  
  

Note: In low power consumption mode, the average current of LDO VOUT 3.3V is about 30 μA, and the maximum current is about 1.6 mA. When it is at the peak, the touch sensor is in the measurement state.

• The current sampling diagram of the LDO VIN 5V terminal in low power mode is as follows (including the current consumed by ESP32, display, sensor, and LDO):
  
  

Note: In low power consumption mode, the average current of LDO VIN 5V is about 45 μA, and the maximum current is about 2.1 mA.

OLED Demo compile and run

Preliminary preparation

First of all, you need to make sure that the ESP32 toolchain has been installed on your computer. For toolchain installation, please refer to the ESP-IDFREADME.md。

Get the IoT Solution project code

Execute the instruction to download the iot-solution project warehouse:

• You can directly get the warehouse code recursively, which will automatically initialize all the required submodules:

  git clone --recursive https://github.com/espressif/esp-iot-solution.git
  

• You can also manually initialize the sub-module, first run the following command:

  git clone https://github.com/espressif/esp-iot-solution.git

  • Then switch to the project root directory and execute the following instructions to download some other submodules that this project depends on:

  git submodule update --init --recursive

Compile and run

After the submodule code download is complete, the oled_screen_module in the Iot Solution project can be compiled and run. Switch to the esp-iot-solution/examples/oled_screen_module directory, and then perform the following steps.

• Serial port parameter setting

Execute the following commands to compile and configure, such as serial port number and serial download speed can beSerial flasher config Configure in this menu option (if you don’t need to configure, you can skip this step).

    cd YOUR_IOT_SOLUTION_PATH/examples/oled_screen_module
    make menuconfig

• Compile, flash and run

Execute the following command to compile oled_screen_module. In the following command, flash is the download command, and monitor means to open the system for printing. You can choose to add it according to the actual situation.

    make flash monitor

Note: When downloading the program, if the download cannot start automatically, you can try to enter the download mode manually. After downloading the firmware, press the reset button on the development board to re-run the program, you can view the serial port print.