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Have you ever encountered this?
When using the ESP32-C3-MINI-1U module with ESP-IDF version idf5.0.1, there is a probability of failure when waking up from sleep mode, causing the module to hang with no information printed to the serial port. Why is this happening?
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What’s going on?
The mainboard is powered by 220V AC. When the power is off, the module enters sleep mode, and after powering on, the mainboard uses GPIO3 to output a low level to wake up the module. The GPIO3 signal control circuit is shown in the figure below:
(1)After powering on the mainboard, we found that the mainboard indicator light did not light up, and there was no information printed to the serial port. After shorting the module EN pin, the mainboard indicator light returned to normal, and the serial port printed information showing that the module started successfully.
(2)Using a multimeter to measure the module’s power supply voltage, the voltage is normal.
(3)Using an oscilloscope to capture the GPIO3 pin signal waveform, we found that the GPIO3 signal waveform was jittery (waveform shown in the figure below), and the voltage waveform decreased slowly due to the electrical characteristics of the chip pin (the low-level input voltage range for the chip pin is -0.3V~0.825V, and the high-level input voltage range is 2.475V~3.33V, as shown in the figure below), resulting in a gap in the chip’s judgment between high and low levels. Therefore, the judgment of voltage jitter leads to unstable signal output.
(4)By changing the filter capacitor value of GPIO3, we eliminated the signal jitter (waveform shown in the figure below), reducing the probability of the module waking up failure.
(5)By bypassing the AC to DC rectification circuit on the mainboard and directly inputting DC voltage instead of power supply, after retesting, we found that the module wake-up failure did not occur again. After capturing the GPIO3 signal again, we found that the falling time became faster (waveform shown in the figure below), and the difference was significant. It was determined that the rectification conversion circuit interfered with the GPIO3 level signal.
(6) Through the above process, we confirmed that the module wake-up failure was caused by the rectification circuit on the front end of the mainboard, which led to GPIO3 signal jitter and slow voltage drop.
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What should we do now?
SO easy!Change the GPIO3 filter capacitor to improve signal jitter; optimize the PCB design to reduce power supply electromagnetic interference.
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Did you learn it?
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