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Updated Protocol and compatibility (markdown)

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sh123 2021-11-15 10:32:00 +02:00
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Protocol-and-compatibility.md

@ -22,7 +22,8 @@ At the link level, APRS uses the AX.25 protocol, as defined in AmateurPacket-Rad
## APRS compressed packets
In compressed data format, the Information field contains the station’s latitude and longitude, together with course and speed or pre-calculated radio range or altitude. This information is compressed to minimize the length of the transmitted packet (and therefore improve its chances of being received correctly under less than ideal conditions). The Information field also contains a display Symbol Code, and there may optionally be a plain text comment (uncompressed) as well.
![alt text](https://raw.githubusercontent.com/sh123/esp32_loraprs/master/images/aprs_compressed.png)
![alt text](https://raw.githubusercontent.com/sh123/esp32_loraprs/blob/master/images/aprs_compressed.png)
# APRS TNC2 text protocol
TNC2 protocol does not use KISS, it sends text based APRS messages, multiple messages are separated by using new line character `\n`. This is quite inefficient protocol for LoRa, because packet lengths are much longer compared to AX25, which causes longer TOA (time on the air).