Espressif Systems ESP Faq page 169

Chapter 5. Hardware related
5.1.3 Can the GPIO34 ~ GPIO39 of ESP32 only be set to input mode?
• Yes, the GPIO34 ~ GPIO39 of ESP32 can only be set to input mode. They cannot be set to the output mode
as they cannot be pulled up or down by software.
• For more details, please refer to
5.1.4 Does ESP32 support a driver for Linux?
Yes, please refer to the example esp-hosted.
Note: This example is adapted to the 802.3 protocol rather than the 802.11 protocol.
5.1.5 What is the meaning of the acquired data when you scan the data matrix on the
module's shielding case?
• Taking 0920118CAAB5D2B7B4 as an example. '09'indicates the factory code; '20'indicates the last
two numbers of the year of manufacturing, which is 2020 in this example; '11'indicates the week number
of manufacturing; and the last 12 numbers '8CAAB5D2B7B4'is the MAC address of this module. For the
latest information, please refer to
5.1.6 Can VDD3P3_RTC of ESP32 support independent battery power supply?
• The internal RTC of ESP32 cannot work independently as it requires the main CPU to participate in the
configuration. Even if the RTC domain is powered by an independent battery, it may still be powered down
suddenly.
• If you want to save the clock information when power-off occurs, please use an external RTC clock chip.
5.1.7 What is the difference between ESP32-PICO-D4, ESP32-PICO-V3, and ESP32-
PICO-V3-02?
• Built-in chip version: The core chip of ESP32-PICO-V3 and ESP32-PICO-V3-02 is ESP32 (ECO V3), while
that of ESP32-PICO-D4 is ESP32 (ECO V1).
• Package size: The size of ESP32-PICO-D4 and ESP32-PICO-V3 is 7 × 7 × 0.94 (mm), while the size of
ESP32-PICO-V3-02 is 7 × 7 × 1.11 (mm).
• Built-in flash: ESP32-PICO-D4 and ESP32-PICO-V3 integrate 4 MB SPI Flash, while ESP32-PICO-V3-02
integrates 8 MB flash and 2 MB PSRAM.
• Pin differences: Please refer to Section Compatibility with ESP32- PICO- V3 in the
Datasheet.
5.1.8 Does ESP8266 support 32 MHz crystal?
• No. Currently, ESP8266 supports 26 MHz and 40 MHz crystals, and the 26 MHz crystal is recommended.
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GPIO & RTC GPIO.
Module Packaging Information.
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ESP32 -PICO- V3- 02
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