handiko / arduino-aprs Goto Github PK

The copy of APRS101.PDF that you have is about 25 years old.
A lot has changed since then.
You can find the latest at: https://github.com/wb2osz/aprsspec

73,
John WB2OSZ

If you listen to the audio output of pin 2 using the Hello World example, you will notice that the preamble has a high pitch on every other transmission. Printing the first bit of each message looks like this:

MYCALL-1>APRS,WIDE2-1:>Hello World !!
1
MYCALL-1>APRS,WIDE2-1:>Hello World !!
0
MYCALL-1>APRS,WIDE2-1:>Hello World !!
1
MYCALL-1>APRS,WIDE2-1:>Hello World !!
0
MYCALL-1>APRS,WIDE2-1:>Hello World !!
1

The AFSK tones must be reversed on each transmission. Is this the expected operation?

Also, the comment says that the crc is calculated with 0x1024 but the code uses 0x8408:

/*

• This function will calculate CRC-16 CCITT for the FCS (Frame Check Sequence)
• as required for the HDLC frame validity check.
• Using 0x1021 as polynomial generator. The CRC registers are initialized with
• 0xFFFF
  */
  void calc_crc(bool in_bit)
  {
  unsigned short xor_in;

xor_in = crc ^ in_bit; // bitwise XOR
crc >>= 1;

if(xor_in & 0x01)
crc ^= 0x8408;
.
.
.

I see that you use 1200 and 2400 Hz tones everywhere. Shouldn't APRS use 1200 and 2200, as originally?

audio nya ada di speaker, tapi di bila TX, DireWolf tidak bisa decode. kenapa yer?

Hi, in simple aprs with arduino why do you use 2400 hz tone ?
It's supposed to be 2200 hz no ?

Hy,

I'm using the code on an ESP32. With the following Code:

set_pin(26);
set_callsign("OE3FKG", "OE3FKG");
send_packet(_STATUS, 0);

I recorded the output directly in Audacity and the AFSK signal seems a bit short: http://sndup.net/5k9q2

Do I have to change baud_adj? If so, to what value?

Thanks!

Hi @handiko ,
great work!
I'm sharing your project on my own open source catalog repository :
https://github.com/aeonSolutions/AeonLabs-APRS-CWOP-Library/