Chapter 4. Software framework
4.4.2 Digital-to-Analog Converter (DAC)
When using DAC output for ESP32-S2-Saola-1, the power supply is 3.3 V. But the actual tested voltage is
only 3.1 V. Why?
Due to the internal voltage drop, even when using 3.3 V power supply, the actual maximum output is
only about 3.2 V.
4.4.3 GPIO & RTC GPIO
What should I pay attention to for ESP32 pin congurations?
The ESP32 has ESP32-WROOM and ESP32-WROVER series modules. Please pay attention to the
following congurations with GPIOs.
The WROOM-32/32D/32U series have 26 pins available for customers. Please note:
• GPIO6 ~ GPIO11 are used by the internal ash and cannot be used elsewhere;
• GPIO34, 35, 36 and 39 are input-only pins and cannot be used for outputs;
• The ESP32 has a built-in GPIO Matrix, and some peripheral interfaces can be connected to any
free pins. That is, for hardware designs, there is no need to strictly distribute some functions on
certain pins.
For detailed information, please refer to Table 9 in ESP32 Datasheet.
The WROVER ／ WROVER-I ／ WROVER-B ／ WROVER-IB series have 24 pins available for
customers. Please note:
• GPIO6 ~ GPIO11 are used by the internal ash and cannot be used elsewhere;
• GPIO34, 35, 36 and 39 are input-only pins and cannot be used for outputs;
• For WROVER series, it is not recommended to use GPIO12 for Touch Sensor functions since it
has been pulled up in the module;
• The ESP32 has a built-in Matrix, and some peripheral interfaces can be connected to any free pins.
That is, for hardware designs, there is no need to strictly distribute some functions on certain pins.
For detailed information, please refer to Table 9 in ESP32 Datasheet.
There are three sets of UARTs in ESP32, but only UART0 can be used for downloading with xed pins.
Some ESP8266 GPIOs are high level. What could be the reasons?
• According to the hardware design, some GPIOs are pulled up or down by default. Thus the level of these pins
are not controlled by the program during system initialization, causing some incorrect levels of GPIOs during
the boot process.
• If you expect to use these GPIOs, it is recommended to keep the hardware peripherals be consistent with the
default level status, or adjust level status in software during bootloader process. When using the later method,
you may also encounter temporary level exception.
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