1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
|
#ifndef _MAVLINK_HELPERS_H_
#define _MAVLINK_HELPERS_H_
#include "string.h"
#include "checksum.h"
#include "mavlink_types.h"
#include "mavlink_conversions.h"
#ifndef MAVLINK_HELPER
#define MAVLINK_HELPER
#endif
/*
* Internal function to give access to the channel status for each channel
*/
#ifndef MAVLINK_GET_CHANNEL_STATUS
MAVLINK_HELPER mavlink_status_t* mavlink_get_channel_status(uint8_t chan)
{
static mavlink_status_t m_mavlink_status[MAVLINK_COMM_NUM_BUFFERS];
return &m_mavlink_status[chan];
}
#endif
/*
* Internal function to give access to the channel buffer for each channel
*/
#ifndef MAVLINK_GET_CHANNEL_BUFFER
MAVLINK_HELPER mavlink_message_t* mavlink_get_channel_buffer(uint8_t chan)
{
#if MAVLINK_EXTERNAL_RX_BUFFER
// No m_mavlink_message array defined in function,
// has to be defined externally
#ifndef m_mavlink_message
#error ERROR: IF #define MAVLINK_EXTERNAL_RX_BUFFER IS SET, THE BUFFER HAS TO BE ALLOCATED OUTSIDE OF THIS FUNCTION (mavlink_message_t m_mavlink_buffer[MAVLINK_COMM_NUM_BUFFERS];)
#endif
#else
static mavlink_message_t m_mavlink_buffer[MAVLINK_COMM_NUM_BUFFERS];
#endif
return &m_mavlink_buffer[chan];
}
#endif
/**
* @brief Reset the status of a channel.
*/
MAVLINK_HELPER void mavlink_reset_channel_status(uint8_t chan)
{
mavlink_status_t *status = mavlink_get_channel_status(chan);
status->parse_state = MAVLINK_PARSE_STATE_IDLE;
}
/**
* @brief Finalize a MAVLink message with channel assignment
*
* This function calculates the checksum and sets length and aircraft id correctly.
* It assumes that the message id and the payload are already correctly set. This function
* can also be used if the message header has already been written before (as in mavlink_msg_xxx_pack
* instead of mavlink_msg_xxx_pack_headerless), it just introduces little extra overhead.
*
* @param msg Message to finalize
* @param system_id Id of the sending (this) system, 1-127
* @param length Message length
*/
#if MAVLINK_CRC_EXTRA
MAVLINK_HELPER uint16_t mavlink_finalize_message_chan(mavlink_message_t* msg, uint8_t system_id, uint8_t component_id,
uint8_t chan, uint8_t length, uint8_t crc_extra)
#else
MAVLINK_HELPER uint16_t mavlink_finalize_message_chan(mavlink_message_t* msg, uint8_t system_id, uint8_t component_id,
uint8_t chan, uint8_t length)
#endif
{
// This code part is the same for all messages;
uint16_t checksum;
msg->magic = MAVLINK_STX;
msg->len = length;
msg->sysid = system_id;
msg->compid = component_id;
// One sequence number per component
msg->seq = mavlink_get_channel_status(chan)->current_tx_seq;
mavlink_get_channel_status(chan)->current_tx_seq = mavlink_get_channel_status(chan)->current_tx_seq+1;
checksum = crc_calculate((uint8_t*)&msg->len, length + MAVLINK_CORE_HEADER_LEN);
#if MAVLINK_CRC_EXTRA
crc_accumulate(crc_extra, &checksum);
#endif
mavlink_ck_a(msg) = (uint8_t)(checksum & 0xFF);
mavlink_ck_b(msg) = (uint8_t)(checksum >> 8);
return length + MAVLINK_NUM_NON_PAYLOAD_BYTES;
}
/**
* @brief Finalize a MAVLink message with MAVLINK_COMM_0 as default channel
*/
#if MAVLINK_CRC_EXTRA
MAVLINK_HELPER uint16_t mavlink_finalize_message(mavlink_message_t* msg, uint8_t system_id, uint8_t component_id,
uint8_t length, uint8_t crc_extra)
{
return mavlink_finalize_message_chan(msg, system_id, component_id, MAVLINK_COMM_0, length, crc_extra);
}
#else
MAVLINK_HELPER uint16_t mavlink_finalize_message(mavlink_message_t* msg, uint8_t system_id, uint8_t component_id,
uint8_t length)
{
return mavlink_finalize_message_chan(msg, system_id, component_id, MAVLINK_COMM_0, length);
}
#endif
#ifdef MAVLINK_USE_CONVENIENCE_FUNCTIONS
MAVLINK_HELPER void _mavlink_send_uart(mavlink_channel_t chan, const char *buf, uint16_t len);
/**
* @brief Finalize a MAVLink message with channel assignment and send
*/
#if MAVLINK_CRC_EXTRA
MAVLINK_HELPER void _mav_finalize_message_chan_send(mavlink_channel_t chan, uint8_t msgid, const char *packet,
uint8_t length, uint8_t crc_extra)
#else
MAVLINK_HELPER void _mav_finalize_message_chan_send(mavlink_channel_t chan, uint8_t msgid, const char *packet, uint8_t length)
#endif
{
uint16_t checksum;
uint8_t buf[MAVLINK_NUM_HEADER_BYTES];
uint8_t ck[2];
mavlink_status_t *status = mavlink_get_channel_status(chan);
buf[0] = MAVLINK_STX;
buf[1] = length;
buf[2] = status->current_tx_seq;
buf[3] = mavlink_system.sysid;
buf[4] = mavlink_system.compid;
buf[5] = msgid;
status->current_tx_seq++;
checksum = crc_calculate((uint8_t*)&buf[1], MAVLINK_CORE_HEADER_LEN);
crc_accumulate_buffer(&checksum, packet, length);
#if MAVLINK_CRC_EXTRA
crc_accumulate(crc_extra, &checksum);
#endif
ck[0] = (uint8_t)(checksum & 0xFF);
ck[1] = (uint8_t)(checksum >> 8);
MAVLINK_START_UART_SEND(chan, MAVLINK_NUM_NON_PAYLOAD_BYTES + (uint16_t)length);
_mavlink_send_uart(chan, (const char *)buf, MAVLINK_NUM_HEADER_BYTES);
_mavlink_send_uart(chan, packet, length);
_mavlink_send_uart(chan, (const char *)ck, 2);
MAVLINK_END_UART_SEND(chan, MAVLINK_NUM_NON_PAYLOAD_BYTES + (uint16_t)length);
}
/**
* @brief re-send a message over a uart channel
* this is more stack efficient than re-marshalling the message
*/
MAVLINK_HELPER void _mavlink_resend_uart(mavlink_channel_t chan, const mavlink_message_t *msg)
{
uint8_t ck[2];
ck[0] = (uint8_t)(msg->checksum & 0xFF);
ck[1] = (uint8_t)(msg->checksum >> 8);
MAVLINK_START_UART_SEND(chan, MAVLINK_NUM_NON_PAYLOAD_BYTES + msg->len);
_mavlink_send_uart(chan, (const char *)&msg->magic, MAVLINK_NUM_HEADER_BYTES);
_mavlink_send_uart(chan, _MAV_PAYLOAD(msg), msg->len);
_mavlink_send_uart(chan, (const char *)ck, 2);
MAVLINK_END_UART_SEND(chan, MAVLINK_NUM_NON_PAYLOAD_BYTES + msg->len);
}
#endif // MAVLINK_USE_CONVENIENCE_FUNCTIONS
/**
* @brief Pack a message to send it over a serial byte stream
*/
MAVLINK_HELPER uint16_t mavlink_msg_to_send_buffer(uint8_t *buffer, const mavlink_message_t *msg)
{
memcpy(buffer, (const uint8_t *)&msg->magic, MAVLINK_NUM_NON_PAYLOAD_BYTES + (uint16_t)msg->len);
return MAVLINK_NUM_NON_PAYLOAD_BYTES + (uint16_t)msg->len;
}
union __mavlink_bitfield {
uint8_t uint8;
int8_t int8;
uint16_t uint16;
int16_t int16;
uint32_t uint32;
int32_t int32;
};
MAVLINK_HELPER void mavlink_start_checksum(mavlink_message_t* msg)
{
crc_init(&msg->checksum);
}
MAVLINK_HELPER void mavlink_update_checksum(mavlink_message_t* msg, uint8_t c)
{
crc_accumulate(c, &msg->checksum);
}
/**
* This is a convenience function which handles the complete MAVLink parsing.
* the function will parse one byte at a time and return the complete packet once
* it could be successfully decoded. Checksum and other failures will be silently
* ignored.
*
* @param chan ID of the current channel. This allows to parse different channels with this function.
* a channel is not a physical message channel like a serial port, but a logic partition of
* the communication streams in this case. COMM_NB is the limit for the number of channels
* on MCU (e.g. ARM7), while COMM_NB_HIGH is the limit for the number of channels in Linux/Windows
* @param c The char to barse
*
* @param returnMsg NULL if no message could be decoded, the message data else
* @return 0 if no message could be decoded, 1 else
*
* A typical use scenario of this function call is:
*
* @code
* #include <inttypes.h> // For fixed-width uint8_t type
*
* mavlink_message_t msg;
* int chan = 0;
*
*
* while(serial.bytesAvailable > 0)
* {
* uint8_t byte = serial.getNextByte();
* if (mavlink_parse_char(chan, byte, &msg))
* {
* printf("Received message with ID %d, sequence: %d from component %d of system %d", msg.msgid, msg.seq, msg.compid, msg.sysid);
* }
* }
*
*
* @endcode
*/
MAVLINK_HELPER uint8_t mavlink_parse_char(uint8_t chan, uint8_t c, mavlink_message_t* r_message, mavlink_status_t* r_mavlink_status)
{
/*
default message crc function. You can override this per-system to
put this data in a different memory segment
*/
#if MAVLINK_CRC_EXTRA
#ifndef MAVLINK_MESSAGE_CRC
static const uint8_t mavlink_message_crcs[256] = MAVLINK_MESSAGE_CRCS;
#define MAVLINK_MESSAGE_CRC(msgid) mavlink_message_crcs[msgid]
#endif
#endif
/* Enable this option to check the length of each message.
This allows invalid messages to be caught much sooner. Use if the transmission
medium is prone to missing (or extra) characters (e.g. a radio that fades in
and out). Only use if the channel will only contain messages types listed in
the headers.
*/
#if MAVLINK_CHECK_MESSAGE_LENGTH
#ifndef MAVLINK_MESSAGE_LENGTH
static const uint8_t mavlink_message_lengths[256] = MAVLINK_MESSAGE_LENGTHS;
#define MAVLINK_MESSAGE_LENGTH(msgid) mavlink_message_lengths[msgid]
#endif
#endif
mavlink_message_t* rxmsg = mavlink_get_channel_buffer(chan); ///< The currently decoded message
mavlink_status_t* status = mavlink_get_channel_status(chan); ///< The current decode status
int bufferIndex = 0;
status->msg_received = 0;
switch (status->parse_state)
{
case MAVLINK_PARSE_STATE_UNINIT:
case MAVLINK_PARSE_STATE_IDLE:
if (c == MAVLINK_STX)
{
status->parse_state = MAVLINK_PARSE_STATE_GOT_STX;
rxmsg->len = 0;
rxmsg->magic = c;
mavlink_start_checksum(rxmsg);
}
break;
case MAVLINK_PARSE_STATE_GOT_STX:
if (status->msg_received
/* Support shorter buffers than the
default maximum packet size */
#if (MAVLINK_MAX_PAYLOAD_LEN < 255)
|| c > MAVLINK_MAX_PAYLOAD_LEN
#endif
)
{
status->buffer_overrun++;
status->parse_error++;
status->msg_received = 0;
status->parse_state = MAVLINK_PARSE_STATE_IDLE;
}
else
{
// NOT counting STX, LENGTH, SEQ, SYSID, COMPID, MSGID, CRC1 and CRC2
rxmsg->len = c;
status->packet_idx = 0;
mavlink_update_checksum(rxmsg, c);
status->parse_state = MAVLINK_PARSE_STATE_GOT_LENGTH;
}
break;
case MAVLINK_PARSE_STATE_GOT_LENGTH:
rxmsg->seq = c;
mavlink_update_checksum(rxmsg, c);
status->parse_state = MAVLINK_PARSE_STATE_GOT_SEQ;
break;
case MAVLINK_PARSE_STATE_GOT_SEQ:
rxmsg->sysid = c;
mavlink_update_checksum(rxmsg, c);
status->parse_state = MAVLINK_PARSE_STATE_GOT_SYSID;
break;
case MAVLINK_PARSE_STATE_GOT_SYSID:
rxmsg->compid = c;
mavlink_update_checksum(rxmsg, c);
status->parse_state = MAVLINK_PARSE_STATE_GOT_COMPID;
break;
case MAVLINK_PARSE_STATE_GOT_COMPID:
#if MAVLINK_CHECK_MESSAGE_LENGTH
if (rxmsg->len != MAVLINK_MESSAGE_LENGTH(c))
{
status->parse_error++;
status->parse_state = MAVLINK_PARSE_STATE_IDLE;
break;
if (c == MAVLINK_STX)
{
status->parse_state = MAVLINK_PARSE_STATE_GOT_STX;
mavlink_start_checksum(rxmsg);
}
}
#endif
rxmsg->msgid = c;
mavlink_update_checksum(rxmsg, c);
if (rxmsg->len == 0)
{
status->parse_state = MAVLINK_PARSE_STATE_GOT_PAYLOAD;
}
else
{
status->parse_state = MAVLINK_PARSE_STATE_GOT_MSGID;
}
break;
case MAVLINK_PARSE_STATE_GOT_MSGID:
_MAV_PAYLOAD_NON_CONST(rxmsg)[status->packet_idx++] = (char)c;
mavlink_update_checksum(rxmsg, c);
if (status->packet_idx == rxmsg->len)
{
status->parse_state = MAVLINK_PARSE_STATE_GOT_PAYLOAD;
}
break;
case MAVLINK_PARSE_STATE_GOT_PAYLOAD:
#if MAVLINK_CRC_EXTRA
mavlink_update_checksum(rxmsg, MAVLINK_MESSAGE_CRC(rxmsg->msgid));
#endif
if (c != (rxmsg->checksum & 0xFF)) {
// Check first checksum byte
status->parse_error++;
status->msg_received = 0;
status->parse_state = MAVLINK_PARSE_STATE_IDLE;
if (c == MAVLINK_STX)
{
status->parse_state = MAVLINK_PARSE_STATE_GOT_STX;
rxmsg->len = 0;
mavlink_start_checksum(rxmsg);
}
}
else
{
status->parse_state = MAVLINK_PARSE_STATE_GOT_CRC1;
_MAV_PAYLOAD_NON_CONST(rxmsg)[status->packet_idx] = (char)c;
}
break;
case MAVLINK_PARSE_STATE_GOT_CRC1:
if (c != (rxmsg->checksum >> 8)) {
// Check second checksum byte
status->parse_error++;
status->msg_received = 0;
status->parse_state = MAVLINK_PARSE_STATE_IDLE;
if (c == MAVLINK_STX)
{
status->parse_state = MAVLINK_PARSE_STATE_GOT_STX;
rxmsg->len = 0;
mavlink_start_checksum(rxmsg);
}
}
else
{
// Successfully got message
status->msg_received = 1;
status->parse_state = MAVLINK_PARSE_STATE_IDLE;
_MAV_PAYLOAD_NON_CONST(rxmsg)[status->packet_idx+1] = (char)c;
memcpy(r_message, rxmsg, sizeof(mavlink_message_t));
}
break;
}
bufferIndex++;
// If a message has been sucessfully decoded, check index
if (status->msg_received == 1)
{
//while(status->current_seq != rxmsg->seq)
//{
// status->packet_rx_drop_count++;
// status->current_seq++;
//}
status->current_rx_seq = rxmsg->seq;
// Initial condition: If no packet has been received so far, drop count is undefined
if (status->packet_rx_success_count == 0) status->packet_rx_drop_count = 0;
// Count this packet as received
status->packet_rx_success_count++;
}
r_mavlink_status->current_rx_seq = status->current_rx_seq+1;
r_mavlink_status->packet_rx_success_count = status->packet_rx_success_count;
r_mavlink_status->packet_rx_drop_count = status->parse_error;
status->parse_error = 0;
return status->msg_received;
}
/**
* @brief Put a bitfield of length 1-32 bit into the buffer
*
* @param b the value to add, will be encoded in the bitfield
* @param bits number of bits to use to encode b, e.g. 1 for boolean, 2, 3, etc.
* @param packet_index the position in the packet (the index of the first byte to use)
* @param bit_index the position in the byte (the index of the first bit to use)
* @param buffer packet buffer to write into
* @return new position of the last used byte in the buffer
*/
MAVLINK_HELPER uint8_t put_bitfield_n_by_index(int32_t b, uint8_t bits, uint8_t packet_index, uint8_t bit_index, uint8_t* r_bit_index, uint8_t* buffer)
{
uint16_t bits_remain = bits;
// Transform number into network order
int32_t v;
uint8_t i_bit_index, i_byte_index, curr_bits_n;
#if MAVLINK_NEED_BYTE_SWAP
union {
int32_t i;
uint8_t b[4];
} bin, bout;
bin.i = b;
bout.b[0] = bin.b[3];
bout.b[1] = bin.b[2];
bout.b[2] = bin.b[1];
bout.b[3] = bin.b[0];
v = bout.i;
#else
v = b;
#endif
// buffer in
// 01100000 01000000 00000000 11110001
// buffer out
// 11110001 00000000 01000000 01100000
// Existing partly filled byte (four free slots)
// 0111xxxx
// Mask n free bits
// 00001111 = 2^0 + 2^1 + 2^2 + 2^3 = 2^n - 1
// = ((uint32_t)(1 << n)) - 1; // = 2^n - 1
// Shift n bits into the right position
// out = in >> n;
// Mask and shift bytes
i_bit_index = bit_index;
i_byte_index = packet_index;
if (bit_index > 0)
{
// If bits were available at start, they were available
// in the byte before the current index
i_byte_index--;
}
// While bits have not been packed yet
while (bits_remain > 0)
{
// Bits still have to be packed
// there can be more than 8 bits, so
// we might have to pack them into more than one byte
// First pack everything we can into the current 'open' byte
//curr_bits_n = bits_remain << 3; // Equals bits_remain mod 8
//FIXME
if (bits_remain <= (uint8_t)(8 - i_bit_index))
{
// Enough space
curr_bits_n = (uint8_t)bits_remain;
}
else
{
curr_bits_n = (8 - i_bit_index);
}
// Pack these n bits into the current byte
// Mask out whatever was at that position with ones (xxx11111)
buffer[i_byte_index] &= (0xFF >> (8 - curr_bits_n));
// Put content to this position, by masking out the non-used part
buffer[i_byte_index] |= ((0x00 << curr_bits_n) & v);
// Increment the bit index
i_bit_index += curr_bits_n;
// Now proceed to the next byte, if necessary
bits_remain -= curr_bits_n;
if (bits_remain > 0)
{
// Offer another 8 bits / one byte
i_byte_index++;
i_bit_index = 0;
}
}
*r_bit_index = i_bit_index;
// If a partly filled byte is present, mark this as consumed
if (i_bit_index != 7) i_byte_index++;
return i_byte_index - packet_index;
}
#ifdef MAVLINK_USE_CONVENIENCE_FUNCTIONS
// To make MAVLink work on your MCU, define comm_send_ch() if you wish
// to send 1 byte at a time, or MAVLINK_SEND_UART_BYTES() to send a
// whole packet at a time
/*
#include "mavlink_types.h"
void comm_send_ch(mavlink_channel_t chan, uint8_t ch)
{
if (chan == MAVLINK_COMM_0)
{
uart0_transmit(ch);
}
if (chan == MAVLINK_COMM_1)
{
uart1_transmit(ch);
}
}
*/
MAVLINK_HELPER void _mavlink_send_uart(mavlink_channel_t chan, const char *buf, uint16_t len)
{
#ifdef MAVLINK_SEND_UART_BYTES
/* this is the more efficient approach, if the platform
defines it */
MAVLINK_SEND_UART_BYTES(chan, (const uint8_t *)buf, len);
#else
/* fallback to one byte at a time */
uint16_t i;
for (i = 0; i < len; i++) {
comm_send_ch(chan, (uint8_t)buf[i]);
}
#endif
}
#endif // MAVLINK_USE_CONVENIENCE_FUNCTIONS
#endif /* _MAVLINK_HELPERS_H_ */
|