4 * This file is part of BeRTOS.
6 * Bertos is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 * As a special exception, you may use this file as part of a free software
21 * library without restriction. Specifically, if other files instantiate
22 * templates or use macros or inline functions from this file, or you compile
23 * this file and link it with other files to produce an executable, this
24 * file does not by itself cause the resulting executable to be covered by
25 * the GNU General Public License. This exception does not however
26 * invalidate any other reasons why the executable file might be covered by
27 * the GNU General Public License.
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 msg.dst.ssid = (*buf++ >> 1) & 0x0F;
68 DECODE_CALL(buf, msg.src.call);
69 msg.src.ssid = (*buf >> 1) & 0x0F;
71 LOG_INFO("SRC[%.6s-%d], DST[%.6s-%d]\n", msg.src.call, msg.src.ssid, msg.dst.call, msg.dst.ssid);
73 /* Repeater addresses */
74 #if CONFIG_AX25_RPT_LST
75 for (msg.rpt_cnt = 0; !(*buf++ & 0x01) && (msg.rpt_cnt < countof(msg.rpt_lst)); msg.rpt_cnt++)
77 DECODE_CALL(buf, msg.rpt_lst[msg.rpt_cnt].call);
78 msg.rpt_lst[msg.rpt_cnt].ssid = (*buf >> 1) & 0x0F;
79 LOG_INFO("RPT%d[%.6s-%d]\n", msg.rpt_cnt, msg.rpt_lst[msg.rpt_cnt].call, msg.rpt_lst[msg.rpt_cnt].ssid);
82 while (!(*buf++ & 0x01))
86 DECODE_CALL(buf, rpt);
87 ssid = (*buf >> 1) & 0x0F;
88 LOG_INFO("RPT[%.6s-%d]\n", rpt, ssid);
93 if (msg.ctrl != AX25_CTRL_UI)
95 LOG_WARN("Only UI frames are handled, got [%02X]\n", msg.ctrl);
100 if (msg.pid != AX25_PID_NOLAYER3)
102 LOG_WARN("Only frames without layer3 protocol are handled, got [%02X]\n", msg.pid);
106 msg.len = ctx->frm_len - 2 - (buf - ctx->buf);
108 LOG_INFO("DATA: %.*s\n", msg.len, msg.info);
116 * Check if there are any AX25 messages to be processed.
117 * This function read available characters from the medium and search for
119 * If a message is found it is decoded and the linked callback executed.
120 * This function may be blocking if there are no available chars and the KFile
121 * used in \a ctx to access the medium is configured in blocking mode.
123 * \param ctx AX25 context to operate on.
125 void ax25_poll(AX25Ctx *ctx)
129 while ((c = kfile_getc(ctx->ch)) != EOF)
131 if (!ctx->escape && c == HDLC_FLAG)
133 if (ctx->frm_len >= AX25_MIN_FRAME_LEN)
135 if (ctx->crc_in == AX25_CRC_CORRECT)
137 LOG_INFO("Frame found!\n");
142 LOG_INFO("CRC error, computed [%04X]\n", ctx->crc_in);
146 ctx->crc_in = CRC_CCITT_INIT_VAL;
151 if (!ctx->escape && c == HDLC_RESET)
153 LOG_INFO("HDLC reset\n");
158 if (!ctx->escape && c == AX25_ESC)
166 if (ctx->frm_len < CONFIG_AX25_FRAME_BUF_LEN)
168 ctx->buf[ctx->frm_len++] = c;
169 ctx->crc_in = updcrc_ccitt(c, ctx->crc_in);
173 LOG_INFO("Buffer overrun");
180 if (kfile_error(ctx->ch))
182 LOG_ERR("Channel error [%04x]\n", kfile_error(ctx->ch));
183 kfile_clearerr(ctx->ch);
187 static void ax25_putchar(AX25Ctx *ctx, uint8_t c)
189 if (c == HDLC_FLAG || c == HDLC_RESET
191 kfile_putc(AX25_ESC, ctx->ch);
192 ctx->crc_out = updcrc_ccitt(c, ctx->crc_out);
193 kfile_putc(c, ctx->ch);
196 static void ax25_sendCall(AX25Ctx *ctx, const AX25Call *addr)
198 unsigned len = MIN(sizeof(addr->call), strlen(addr->call));
200 for (unsigned i = 0; i < len; i++)
202 uint8_t c = addr->call[i];
203 ASSERT(isalnum(c) || c == ' ');
205 ax25_putchar(ctx, c << 1);
208 /* Fill with spaces the rest of the CALL if it's shorter */
209 if (len < sizeof(addr->call))
210 for (unsigned i = 0; i < sizeof(addr->call) - len; i++)
211 ax25_putchar(ctx, ' ' << 1);
215 * Send an AX25 frame on the channel.
216 * \param ctx AX25 context to operate on.
217 * \param dst the destination callsign for the frame, \see AX25_CALL
218 * for a handy way to create a callsign on the fly.
219 * \param src the source callsign for the frame, \see AX25_CALL
220 * for a handy way to create a callsign on the fly.
221 * \param _buf payload buffer.
222 * \param len length of the payload.
224 void ax25_send(AX25Ctx *ctx, const AX25Call *dst, const AX25Call *src, const void *_buf, size_t len)
226 const uint8_t *buf = (const uint8_t *)_buf;
228 ctx->crc_out = CRC_CCITT_INIT_VAL;
229 kfile_putc(HDLC_FLAG, ctx->ch);
231 ax25_sendCall(ctx, dst);
232 ax25_putchar(ctx, dst->ssid << 1);
234 ax25_sendCall(ctx, src);
235 ax25_putchar(ctx, (src->ssid << 1) | 0x01);
236 ax25_putchar(ctx, AX25_CTRL_UI);
237 ax25_putchar(ctx, AX25_PID_NOLAYER3);
240 ax25_putchar(ctx, *buf++);
243 * According to AX25 protocol,
244 * CRC is sent in reverse order!
246 uint8_t crcl = (ctx->crc_out & 0xff) ^ 0xff;
247 uint8_t crch = (ctx->crc_out >> 8) ^ 0xff;
248 ax25_putchar(ctx, crcl);
249 ax25_putchar(ctx, crch);
251 ASSERT(ctx->crc_out == AX25_CRC_CORRECT);
253 kfile_putc(HDLC_FLAG, ctx->ch);
258 * Init the AX25 protocol decoder.
260 * \param ctx AX25 context to init.
261 * \param channel Used to gain access to the physical medium
262 * \param hook Callback function called when a message is received
264 void ax25_init(AX25Ctx *ctx, KFile *channel, ax25_callback_t hook)
269 memset(ctx, 0, sizeof(*ctx));
272 ctx->crc_in = ctx->crc_out = CRC_CCITT_INIT_VAL;