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29 * Copyright 2009 Develer S.r.l. (http://www.develer.com/)
32 * \brief Simple AX25 data link layer implementation.
34 * For now, only UI frames without any Layer 3 protocol are handled.
35 * This however is enough to send/receive APRS packets.
38 * \author Francesco Sacchi <batt@develer.com>
43 #include "cfg/cfg_ax25.h"
46 #include <algo/crc_ccitt.h>
48 #define LOG_LEVEL AX25_LOG_LEVEL
49 #define LOG_FORMAT AX25_LOG_FORMAT
52 #include <string.h> //memset
54 #define DECODE_CALL(buf, addr) \
55 for (unsigned i = 0; i < sizeof((addr)); i++) \
57 ASSERT(!(*(buf) & 0x01)); \
58 (addr)[i] = *(buf)++ >> 1; \
61 static void ax25_decode(AX25Ctx *ctx)
64 uint8_t *buf = ctx->buf;
66 DECODE_CALL(buf, msg.dst.call);
67 ASSERT(!(*buf & 0x01));
68 msg.dst.ssid = (*buf++ >> 1) & 0x0F;
70 DECODE_CALL(buf, msg.src.call);
71 msg.src.ssid = (*buf >> 1) & 0x0F;
73 LOG_INFO("SRC[%.6s-%d], DST[%.6s-%d]\n", msg.src.call, msg.src.ssid, msg.dst.call, msg.dst.ssid);
75 /* Repeater addresses */
76 #if CONFIG_AX25_RPT_LST
77 for (msg.rpt_cnt = 0; !(*buf++ & 0x01) && (msg.rpt_cnt < countof(msg.rpt_lst)); msg.rpt_cnt++)
79 DECODE_CALL(buf, msg.rpt_lst[msg.rpt_cnt].call);
80 msg.rpt_lst[msg.rpt_cnt].ssid = (*buf >> 1) & 0x0F;
81 LOG_INFO("RPT%d[%.6s-%d]\n", msg.rpt_cnt, msg.rpt_lst[msg.rpt_cnt].call, msg.rpt_lst[msg.rpt_cnt].ssid);
84 while (!(*buf++ & 0x01))
88 DECODE_CALL(buf, rpt);
89 ssid = (*buf >> 1) & 0x0F;
90 LOG_INFO("RPT[%.6s-%d]\n", rpt, ssid);
95 if (msg.ctrl != AX25_CTRL_UI)
97 LOG_INFO("Only UI frames are handled, got [%02X]\n", msg.ctrl);
102 if (msg.pid != AX25_PID_NOLAYER3)
104 LOG_INFO("Only frames without layer3 protocol are handled, got [%02X]\n", msg.pid);
108 msg.len = ctx->frm_len - 2 - (buf - ctx->buf);
110 LOG_INFO("DATA[%.*s]\n", msg.len, msg.info);
116 void ax25_poll(AX25Ctx *ctx)
120 while ((c = kfile_getc(ctx->ch)) != EOF)
122 if (!ctx->escape && c == HDLC_FLAG)
124 LOG_INFO("Frame start\n");
125 if (ctx->frm_len >= AX25_MIN_FRAME_LEN)
127 if (ctx->crc_in == AX25_CRC_CORRECT)
129 LOG_INFO("Frame found!\n");
134 LOG_INFO("CRC error, computed [%04X]\n", ctx->crc_in);
138 ctx->crc_in = CRC_CCITT_INIT_VAL;
143 if (!ctx->escape && c == HDLC_RESET)
145 LOG_INFO("HDLC reset\n");
150 if (!ctx->escape && c == AX25_ESC)
158 if (ctx->frm_len < CONFIG_AX25_FRAME_BUF_LEN)
160 ctx->buf[ctx->frm_len++] = c;
161 ctx->crc_in = updcrc_ccitt(c, ctx->crc_in);
165 LOG_INFO("Buffer overrun");
172 if (kfile_error(ctx->ch))
174 LOG_ERR("Channel error [%04x]\n", kfile_error(ctx->ch));
175 kfile_clearerr(ctx->ch);
179 void ax25_init(AX25Ctx *ctx, KFile *channel, ax25_callback_t hook)
184 memset(ctx, 0, sizeof(*ctx));
187 ctx->crc_in = ctx->crc_out = CRC_CCITT_INIT_VAL;