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#ifndef _MAVLINK_HELPERS_H_
#define _MAVLINK_HELPERS_H_
#include "string.h"
#include "checksum.h"
#include "mavlink_types.h"
#ifndef MAVLINK_HELPER
#define MAVLINK_HELPER
#endif
/*
internal function to give access to the channel status for each channel
*/
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];
}
/*
internal function to give access to the channel buffer for each channel
*/
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];
}
/**
* @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);
}
#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
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:
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, (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_ */