• https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf

• https://randomnerdtutorials.com/power-esp32-esp8266-solar-panels-battery-level-monitoring/
• https://lastminuteengineers.com/esp32-sleep-modes-power-consumption/
• https://www.instructables.com/id/ESP32-Deep-Sleep-Tutorial/

• https://randomnerdtutorials.com/learn-esp32-with-arduino-ide/

• Tutorial: https://techtutorialsx.com/2018/04/18/esp32-arduino-getting-temperature-from-a-dht22-sensor/
• Library: https://github.com/beegee-tokyo/DHTesp

• https://randomnerdtutorials.com/esp32-dht11-dht22-temperature-humidity-web-server-arduino-ide/
• https://github.com/RuiSantosdotme/Random-Nerd-Tutorials/blob/master/Projects/ESP32/dht22_web_server.ino

• Tutorial: https://www.thethingsnetwork.org/labs/story/heltec-lorawan-gps-quick-start

• https://github.com/mcci-catena/ibm-lmic/blob/master/doc/LMiC-v1.6.pdf

https://heltec.org/project/wifi-lora-32/?lang=en

• WIFI_LoRa_32(868-915version)Schematic_diagram.PDF

• V1: https://github.com/Heltec-Aaron-Lee/WiFi_Kit_series/raw/master/PinoutDiagram/WIFI%20LoRa%2032%20.pdf
• V2: https://github.com/Heltec-Aaron-Lee/WiFi_Kit_series/raw/master/PinoutDiagram/WIFI%20LoRa%2032(V2)%20.pdf

• http://www.heltec.cn/project/wifi-lora-32/?lang=en
• https://www.instructables.com/id/ESP32-Lora-Changing-Frequency/
• https://github.com/Heltec-Aaron-Lee/WiFi_Kit_series/tree/master/esp32/libraries/LoRa
• https://github.com/HelTecAutomation/heltec_lmic
• https://github.com/Heltec-Aaron-Lee/WiFi_Kit_series
• https://github.com/Heltec-Aaron-Lee/WiFi_Kit_series/blob/master/README.md#instructions
• https://github.com/Heltec-Aaron-Lee/WiFi_Kit_series/blob/master/InstallGuide/windows.md
• http://heltec.diytrade.com/sdp/2044581/4/pl-6785993/0.html
• https://hackaday.io/project/27791/logs
• https://hackaday.io/project/27791-esp32-lora-oled-module
• https://www.hackerspace-ffm.de/wiki/index.php?title=Heltec_Wifi_LoRa_32
• https://www.hackster.io/rayburne/lora-and-the-esp32-6ce9ba

• What are GAP, GATT, Server, Client, Master, Slave in BLE?
  https://devzone.nordicsemi.com/f/nordic-q-a/71/what-is-a-client-and-server-in-ble

• TTGO
• TTGO and Heltec comparison: https://www.youtube.com/watch?v=CJNq2I_PDHQ

Seems to be technically completely identical.

• https://github.com/LilyGO/TTGO-T-Beam
• https://blog.hackster.io/the-ttgo-t-beam-an-esp32-lora-board-d44b08f18628
• https://www.youtube.com/watch?v=fK4YQROD9Ps