The handset is powered by ESP32 and has a transflective Sharp LCD controller.
Similar to my previous Chronio smart watch, the focus of the project is low power consumption.
Using the ULP core of the ESP32, the development board can enter the depth sleep of the active display.
The software includes a menu interface with a simple RSS reader.
Some main features are:
- 400X240PX 2.7 "Sharp Memory Display
- 350 mAh lithium polymer battery and USB charging
- 300μW power consumption has been displayed
- 4 to the joystick and button
- Date and time use built-in RTC and NTP synchronization
Be
1 × Sharp LS027B7DH01A
1 × ESP32 development board
1 × 350 MAH 3.7V lithium battery
Be
Although the battery can only power the handheld a few hours, I want to provide a standby mode with low power display. This way, the device will be used as a clock and calendar. To keep the display to act and extend battery life, you need to do something. Although the memory display does not need to continuously refresh through the SPI, it must provide > 1 Hz clock signal to its EXTCOMM pin. Otherwise, the screen shows aging. This means that part of ESP32 needs to remain active in standby mode.
The dual-core and WiFi modems of the ESP32 may power consumption at 70-200mA. But not everyone knows that it has some good power-saving features. In sleep mode, the main kernels of ESP32 are in power-down, thereby falling current to 10μA. During this time, the internal real-time clock controller is still active. The RTC itself does not do a lot, but it can wake up the ESP32's third nuclear ULP coprocessor. This ultra low power processor can perform basic tasks, such as checking sensors or reading and writing pin status, while only about 150μA. It is required for 1 Hz signal. RTC You can use the following command to periodically wake up ULP:
ULP_SET_WAKEUP_PERIOD (0,1000 * 1000);
For a 1 Hz signal, the ULP coprocessor must be programmed in the assembler. Fortunately, espressif has an example of LED flashing, which can do what I want:
The ESP32 can be activated by different wake-up source. For this project, you need GPIO interrupt because just press the button to wake up the device. Two external wakeups are EXT0 and EXT1. EXT0 can only be assigned to a pin, and EXT1 can be assigned to different pins. When using the ULP core, you need to consider the following: only the RTC can access the pin (RTC GPIO). I also found that internal pull-up / pull-down settings were unreliable. I used the hardware drop-down menu in the design.
/ / Wake ESP32 via the buttons on GPIO32 and GPIO33
#Define button_pin_bitmask 0x300000000
ESP_SLEP_ENABLE_EXT1_WAKEUP (Button_pin_bitmask, ESP_EXT1_WAKEUP_ANY_HIGH);
I want to update every other minute. It is impossible to wake up for the ESP32 in a short time:
ESP_SLEP_ENABLE_TIMER_WAKEUP ((60 - NOW .TM_SEC) * 1000000);
In the case of the standby mode, when the ULP or the main core is awakened, the ES32 consumes only a few microamages when the short peak is short. However, other components on the board also need to supply power. The display itself consumes 10μA of current, but it also requires a 5V power supply. Since the voltage of the LIPO battery is only 3.7V, a DC-DC converter is required. After some search, I found MICROCHIP MCP1640. This is a booster regulator with only 19μA. IC is small, only a few external parts are required. The 3.3V power supply of the ESP32 is a bigger problem. It turns out that it is difficult to find a regulator with high output current but static current small, and the regulator can also be manually soldered. I finally got AP2112K, which can provide 600 mA current at 55μA static current. Be
Once there is actual PCB, the actual power consumption is also very difficult. Most μA ranges of μA ranges are too large and cannot be powered by ESP32. It is very tedious to switch or switch wires between the scope. A user who uses stackexchange comes to think of a smart solution
When the current is high, the diode parallel with the multimeter will limit the voltage drop. In sleep mode, the diode hardly allows current to pass. This way, I can use the multimeter to easily measure the power consumption in sleep mode. Be
When ESP32 is in sleep mode, the current is about 97μA. 59μA is caused by 3.3V power supply
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Circuit City original compilation, translated from HackADAY, please indicate the source!
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