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191 lines
4.8 KiB
191 lines
4.8 KiB
#include "kiss.h"
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/*
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* KISS encoder uses two steps:
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*
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* Step 1: encodes the LoRa APRS frame into an AX.25 frame. DONE
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* Step 2: encapsulates the AX.25 frame into a KISS frame. TODO
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*
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* struct aprs_frame {
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* uint8_t source_address[10];
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* uint8_t digi_path[255];
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* uint8_t data_field[255];
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* uint8_t message[255];
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* uint8_t digis[10][10];
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* uint8_t acknowledge_number[255];
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* bool acknowledge_request = false;
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* uint16_t server_command = 0;
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* uint16_t number_of_digipeaters = 0;
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*
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* uint8_t valid_apsr_data = false;
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* };
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*
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*/
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uint16_t KissClass::EncodeFrame(struct aprs_frame *aprsframe, struct ax25_frame *ax25frame)
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{
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uint8_t *encoded_call;
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uint16_t cnt=0;
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uint16_t position = 0;
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uint8_t digi_cnt = 0;
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// Destination call
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//printf("Destination: ");
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encoded_call = EncodeCall(aprsframe->digis[0]);
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cnt = 0;
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while (cnt < 7)
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{
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ax25frame->complete[position] = *(encoded_call+cnt);
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////printf("0x%X ", *(encoded_call+cnt));
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//printf("0x%X ", ax25frame->complete[position]);
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cnt++;
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position++;
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}
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//printf("\n");
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// Source call
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//printf("Source: ");
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cnt=0;
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encoded_call = EncodeCall(aprsframe->source_address);
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while (cnt < 7)
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{
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ax25frame->complete[position] = *(encoded_call+cnt);
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////printf("0x%X ", *(encoded_call+cnt));
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//printf("0x%X ", ax25frame->complete[position]);
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cnt++;
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position++;
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}
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//printf("\n");
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// No digipeaters in path, so destination is the last call and therefore the 'last' flag should be set
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if (aprsframe->number_of_digipeaters == 0)
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{
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ax25frame->complete[position-1] |= 0x01;
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}
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else
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{
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// Path (digipeaters)
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//printf("Path: ");
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cnt=0;
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digi_cnt = 1; // Start at position 1 as position 0 contains destination (which we already encoded)
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while (aprsframe->number_of_digipeaters-- != 0) {
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while (cnt < 7) {
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encoded_call = EncodeCall(aprsframe->digis[digi_cnt]);
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ax25frame->complete[position] = *(encoded_call+cnt);
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////printf("0x%X ", *(encoded_call+cnt));
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//printf("0x%X ", ax25frame->complete[position]);
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cnt++;
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position++;
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}
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digi_cnt++;
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cnt = 0;
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}
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//printf("\n");
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// Set 'last' flag
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ax25frame->complete[position-1] |= 0x01;
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}
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// Add control fields
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ax25frame->complete[position++] = 0x03;
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ax25frame->complete[position++] = 0xF0;
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// All the dificult bits are done, now we just add the payload.
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//printf("Data:");
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cnt = 0;
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while (aprsframe->data_field[cnt] != 0 && cnt < 256) {
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ax25frame->complete[position] = aprsframe->data_field[cnt];
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//printf("0x%X ", ax25frame->complete[position]);
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cnt++;
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position++;
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}
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printf( "\n");
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// Store length of AX25 frame
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ax25frame->lenght = position;
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/*cnt=0;
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while (ax25frame->lenght-- != 0)
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{
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printf("0x%X ", ax25frame->complete[cnt]);
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cnt++;
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}
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printf("\n");
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*/
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//fwrite(ax25frame->complete, 1, ax25frame->lenght, stdout);
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return 0;
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}
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/*
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* Encodes call according to AX.25 specs.
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*
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* input : string with call and ssid as readable characters
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* output: pointer to memory location (7 bytes with the encoded call)
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*
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*/
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uint8_t * KissClass::EncodeCall(uint8_t string[])
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{
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uint8_t position = 0;
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uint8_t cnt = 0;
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static uint8_t call[7] = { 0,0,0,0,0,0,0} ;
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uint8_t ssid = 0;
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// extract call
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while( string[position] != 0 || cnt < 6)
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{
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call[cnt++] = string[position] << 1;
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if ( string[position] == '-') {
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position++;
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break;
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}
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position++;
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}
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// pad with spaces to a length of 6
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while( cnt < 6 )
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{
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call[cnt++] = ' ' << 1;
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}
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// extract ssid
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cnt=0;
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while( string[position] != 0 )
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{
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if (string[position] >= 48 && string[position] <= 57) {
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ssid = 10*ssid + string[position]-48;
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position++;
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}
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}
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// if asterix is pressent in string, than the message has been repeated, so set the 'has been repeated' flag in the ssid register
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position = 0;
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while( string[position] != 0)
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{
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if (string[position] == '*')
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ssid = 0b10000000;
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position++;
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}
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ssid = (ssid << 1) | 0b01100000;
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// add encoded ssid to encoded call array
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call[6] = ssid;
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/*
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//printf("SSID: 0x%X\n", ssid);
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cnt = 0;
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while (cnt < 7)
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{
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//printf("0x%X ", call[cnt++]);
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}
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//printf("\n");
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*/
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return call;
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}
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