4 * This file is part of BeRTOS.
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14 * GNU General Public License for more details.
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18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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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"
45 #include <algo/crc_ccitt.h>
47 #define LOG_LEVEL AX25_LOG_LEVEL
48 #define LOG_FORMAT AX25_LOG_FORMAT
51 #include <string.h> //memset, memcmp
52 #include <ctype.h> //isalnum, toupper
54 #define DECODE_CALL(buf, addr) \
55 for (unsigned i = 0; i < sizeof((addr)); i++) \
57 (addr)[i] = *(buf)++ >> 1; \
60 static void ax25_decode(AX25Ctx *ctx)
63 uint8_t *buf = ctx->buf;
65 DECODE_CALL(buf, msg.dst.call);
66 ASSERT(!(*buf & 0x01));
67 msg.dst.ssid = (*buf++ >> 1) & 0x0F;
69 DECODE_CALL(buf, msg.src.call);
70 msg.src.ssid = (*buf >> 1) & 0x0F;
72 LOG_INFO("SRC[%.6s-%d], DST[%.6s-%d]\n", msg.src.call, msg.src.ssid, msg.dst.call, msg.dst.ssid);
74 /* Repeater addresses */
75 #if CONFIG_AX25_RPT_LST
76 for (msg.rpt_cnt = 0; !(*buf++ & 0x01) && (msg.rpt_cnt < countof(msg.rpt_lst)); msg.rpt_cnt++)
78 DECODE_CALL(buf, msg.rpt_lst[msg.rpt_cnt].call);
79 msg.rpt_lst[msg.rpt_cnt].ssid = (*buf >> 1) & 0x0F;
80 LOG_INFO("RPT%d[%.6s-%d]\n", msg.rpt_cnt, msg.rpt_lst[msg.rpt_cnt].call, msg.rpt_lst[msg.rpt_cnt].ssid);
83 while (!(*buf++ & 0x01))
87 DECODE_CALL(buf, rpt);
88 ssid = (*buf >> 1) & 0x0F;
89 LOG_INFO("RPT[%.6s-%d]\n", rpt, ssid);
94 if (msg.ctrl != AX25_CTRL_UI)
96 LOG_WARN("Only UI frames are handled, got [%02X]\n", msg.ctrl);
101 if (msg.pid != AX25_PID_NOLAYER3)
103 LOG_WARN("Only frames without layer3 protocol are handled, got [%02X]\n", msg.pid);
107 msg.len = ctx->frm_len - 2 - (buf - ctx->buf);
109 LOG_INFO("DATA: %.*s\n", msg.len, msg.info);
115 void ax25_poll(AX25Ctx *ctx)
119 while ((c = kfile_getc(ctx->ch)) != EOF)
121 if (!ctx->escape && c == HDLC_FLAG)
123 if (ctx->frm_len >= AX25_MIN_FRAME_LEN)
125 if (ctx->crc_in == AX25_CRC_CORRECT)
127 LOG_INFO("Frame found!\n");
132 LOG_INFO("CRC error, computed [%04X]\n", ctx->crc_in);
136 ctx->crc_in = CRC_CCITT_INIT_VAL;
141 if (!ctx->escape && c == HDLC_RESET)
143 LOG_INFO("HDLC reset\n");
148 if (!ctx->escape && c == AX25_ESC)
156 if (ctx->frm_len < CONFIG_AX25_FRAME_BUF_LEN)
158 ctx->buf[ctx->frm_len++] = c;
159 ctx->crc_in = updcrc_ccitt(c, ctx->crc_in);
163 LOG_INFO("Buffer overrun");
170 if (kfile_error(ctx->ch))
172 LOG_ERR("Channel error [%04x]\n", kfile_error(ctx->ch));
173 kfile_clearerr(ctx->ch);
177 static void ax25_putchar(AX25Ctx *ctx, uint8_t c)
179 if (c == HDLC_FLAG || c == HDLC_RESET
181 kfile_putc(AX25_ESC, ctx->ch);
182 ctx->crc_out = updcrc_ccitt(c, ctx->crc_out);
183 kfile_putc(c, ctx->ch);
186 static void ax25_sendCall(AX25Ctx *ctx, const AX25Call *addr)
188 unsigned len = MIN(sizeof(addr->call), strlen(addr->call));
190 for (unsigned i = 0; i < len; i++)
192 uint8_t c = addr->call[i];
193 ASSERT(isalnum(c) || c == ' ');
195 ax25_putchar(ctx, c << 1);
198 /* Fill with spaces the rest of the CALL if it's shorter */
199 if (len < sizeof(addr->call))
200 for (unsigned i = 0; i < sizeof(addr->call) - len; i++)
201 ax25_putchar(ctx, ' ' << 1);
204 void ax25_send(AX25Ctx *ctx, const AX25Call *dst, const AX25Call *src, const void *_buf, size_t len)
206 const uint8_t *buf = (const uint8_t *)_buf;
208 ctx->crc_out = CRC_CCITT_INIT_VAL;
209 kfile_putc(HDLC_FLAG, ctx->ch);
211 ax25_sendCall(ctx, dst);
212 ax25_putchar(ctx, dst->ssid << 1);
214 ax25_sendCall(ctx, src);
215 ax25_putchar(ctx, (src->ssid << 1) | 0x01);
216 ax25_putchar(ctx, AX25_CTRL_UI);
217 ax25_putchar(ctx, AX25_PID_NOLAYER3);
220 ax25_putchar(ctx, *buf++);
223 * According to AX25 protocol,
224 * CRC is sent in reverse order!
226 uint8_t crcl = (ctx->crc_out & 0xff) ^ 0xff;
227 uint8_t crch = (ctx->crc_out >> 8) ^ 0xff;
228 ax25_putchar(ctx, crcl);
229 ax25_putchar(ctx, crch);
231 ASSERT(ctx->crc_out == AX25_CRC_CORRECT);
233 kfile_putc(HDLC_FLAG, ctx->ch);
236 void ax25_init(AX25Ctx *ctx, KFile *channel, ax25_callback_t hook)
241 memset(ctx, 0, sizeof(*ctx));
244 ctx->crc_in = ctx->crc_out = CRC_CCITT_INIT_VAL;