Espressif Systems ESP Faq page 136

Chapter 4. Software framework
4.9.12 When ESP8266 is in Deep sleep mode, can the data stored in RTC Memory work?
• When ESP8266 is in Deep sleep mode, only the RTC timer continues to work. The data saved in the RTC
Memory will not run, but can still be saved here. However, the data saved in RTC memory will lose after
ESP8266 is powered off.
4.9.13 What is the maximum length of the NVS Key for ESP32?
• The maximum length of the NVS key for ESP32 is 15 characters, which cannot be changed. Please see the
description of key-value
• But you can use the value of
4.9.14 Does the cJSON in ESP-IDF release/v4.2 support uint64_t data analysis?
• No. The cJSON library has restrictions on parsing long integers, and the longest type is Double.
4.9.15 Given that the GDB debugging function is working before the flash encryption is
disabled, then why does the device keeps restarting during the GDB debugging
after the flash encryption is enabled?
• The JTAG debugging function will be disabled by default when flash encryption or secure boot is enabled. For
more information, please refer to
4.9.16 While using mobile's hotpot for an ESP32 to download the OTA firmware, after
a few seconds when turning of the hotspot and restarts ESP32, the program sticks
in the OTA operation (the same situation for plugging and unplugging the wan
port network cable when using a router), why?
• This is a normal situation based on the protocol. When using the esp_https_ota component to run OTA, you can
set the network timeout value (via http_config->timeout_ms) to 10 ~ 30 s (not too low) and enable http_config-
>keep_alive_enable to see if there are any errors in the link layer.
• If you are using an self-implemented OTA module, please set a timeout value via the select configuration or
enable the TCP keep-alive mechanism to detect the link layer.
4.9.17 Which GPIOs can be used to wake up ESP32-C3 from Deep-Sleep mode?
• Only GPIO0 ~ GPIO5 in VDD3P3_RTC domain can be used to wake up ESP32-C3 from Deep-sleep mode.
Please read Chapter 5.9.1 Power Supplies of GPIO Pins in
Espressif Systems
pair.
nvs_set_str() to store data.
JTAG with Flash Encryption or Secure
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Boot.
ESP32-C3 Technical Reference Manual.
Release master