Experimental LoRa APRS ESP32 APRSDroid bluetooth modem and LoRa APRS-IS iGate

Tiny experimental amateur radio esp32 based LoRa APRSDroid bluetooth modem and iGate server.

Can be used in two modes:

as LoRa APRS client, you need to use APRSDroid application, connect to the modem using bluetooth, data will be re-transmitted through the LoRA radio, this is similar to APRSDroid micromodem - https://unsigned.io/micromodem/, received data will be sent back to the APRSDroid using bluetooth
as a LoRa APRS iGate server, which connects to your WiFI and forwards received LoRA APRS positions into the APRS-IS network, it also reports client signal level, by appending it into the APRS comment

Software Dependencies

Arduino ESP32 library: https://github.com/espressif/arduino-esp32 library (install using arduino library manager)
LoRa arduino library: https://github.com/sandeepmistry/arduino-LoRa (install using arduino library manager)

when setting up APRSDroid, use "TNC (plaintext TNC2)" connection protocol in Connection Preferences -> Connection Protocol
go to esp32_loraprs.ino and make next changes based on your requirements
- comment out / remove LORAPRS_CLIENT define if you are planning to run server mode iGate
- for server mode fill LORAPRS_WIFI_SSID and LORAPRS_WIFI_KEY with your WiFI AP data
- for server mode fill LORAPRS_LOGIN and LORAPRS_PASS with APRS-IS login callsign and pass
- change LORAPRS_FREQ if you are planning to use different frequency, currently it is set to 432.500MHz, which is 70cm band APRS frequency in IARU-1 region, see http://info.aprs.net/index.php?title=Frequencies
if you are planning to use different esp32 pinouts then modify loraprs.h
- lora module CfgPinSs, pin 5
- lora module CfgPinRst, pin 26
- lora module CfgPinDio0, pin 14
if you are planning to experiment with different bandwidths/spread factors then modify loraprs.h
- lora bandwidth CfgBw, 20 kHz (to fit into standard 25 kHz channel)
- lora spread factor CfgSpread, 11 (should decode down to -17.5dB)
- lora coding rate CfgCodingRate, 7
- lora output power CfgPower, 20 (max 20 dBm ~ 100mW, change to lower value if needed)
use 80 MHz ESP32 frequency in Arduino, it will prolong battery life when operating portable, higher CPU speed is not required, there are no CPU intensive operations

Antennas
- Client - rubber duck antenna
- Server - 6 element UHF yagi indoors
Range
- About 4 km when server is 30m above the ground and client is 2m above the ground
- About 13 km when server is 30m above the ground and client is at some higher point ~40m above the ground