If you use configTime, it will create a sntp task that will attempt to connect to an NTP server (every 60 minutes)- no additional config necessary. After you call it, you can call getLocalTime with a timeout (the second parameter), or set a timer if you want it non-blocking. If it fails to get the t...

This is a good read, and includes some examples of calibration. https://github.com/espressif/arduino-esp32/issues/1804
SAR is always going to be biased towards the ends of the scale, and the esp32 seems particularly insensitive there.

MAX on any enum value is typically a dummy value set so that if you are iterating over the values, you know you have reached the end. It has no meaning. WIFI_OFF == WIFI_MODE_NULL.

If you are storing the data for processing, it will be more efficient all the way down the line to work with integers rather than decimals. Efficiency = lower cost. APIs are really for computers to interact (efficiently when possible). The presentation to your eyeballs is the only place where it is ...

The temperature/humidity sensors have very limited memory, so they save space wherever possible. On a device that measures temperature from 0-100, you can get away with a 10-bit integer register (2^10=1024) to store it, with one decimal place of precision. A float value is 32 bits, and more complica...

There is a bootloader. You can set the bootloader to download by strapping gpio0 to ground. Use an IDE or the bootloader utility (https://github.com/espressif/esptool) to upload your firmware.

In most file systems, there is a minimum physical file size. This means that even if the file is only 1 byte of content, it will use a full block when written to disk. I am not familiar with SPIFFS internals, but the physical block size on SPI_Flash is 4096, so that is probably the filesystem block ...

Safety mode will be introduced in ESP-IDF v4.0. Arduino-esp32 v1.0.4 uses IDF v3.2. When v4.0 is released and stable, arduino will update to that upstream version. However, using an advanced feature like this will always require you to compile your own libraries. There are no guarantees that all the...

Using a percentage is misleading, most people recognize the "bars" for signal strength better than a number. https://www.netspotapp.com/what-is-rssi-level.html It is better to send the strength as collected, and let the server (or consumer) on the other end do the conversion. Raw data is more accura...

WiFi.getMode();

https://docs.espressif.com/projects/esp ... ifi_mode_t