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ardupilot/libraries/GCS_MAVLink/include/protocol.h

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#ifndef _MAVLINK_PROTOCOL_H_
#define _MAVLINK_PROTOCOL_H_
#include "string.h"
#include "checksum.h"
#include "mavlink_types.h"
/**
* @brief Initialize the communication stack
*
* This function has to be called before using commParseBuffer() to initialize the different status registers.
*
* @return Will initialize the different buffers and status registers.
*/
static void mavlink_parse_state_initialize(mavlink_status_t* initStatus)
{
if ((initStatus->parse_state <= MAVLINK_PARSE_STATE_UNINIT) || (initStatus->parse_state > MAVLINK_PARSE_STATE_GOT_CRC1))
{
initStatus->ck_a = 0;
initStatus->ck_b = 0;
initStatus->msg_received = 0;
initStatus->buffer_overrun = 0;
initStatus->parse_error = 0;
initStatus->parse_state = MAVLINK_PARSE_STATE_UNINIT;
initStatus->packet_idx = 0;
initStatus->packet_rx_drop_count = 0;
initStatus->packet_rx_success_count = 0;
initStatus->current_rx_seq = 0;
initStatus->current_tx_seq = 0;
}
}
static inline 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];
}
/**
* @brief Finalize a MAVLink message with MAVLINK_COMM_0 as default channel
*
* 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.
*
* @warning This function implicitely assumes the message is sent over channel zero.
* if the message is sent over a different channel it will reach the receiver
* without error, BUT the sequence number might be wrong due to the wrong
* channel sequence counter. This will result is wrongly reported excessive
* packet loss. Please use @see mavlink_{pack|encode}_headerless and then
* @see mavlink_finalize_message_chan before sending for a correct channel
* assignment. Please note that the mavlink_msg_xxx_pack and encode functions
* assign channel zero as default and thus induce possible loss counter errors.\
* They have been left to ensure code compatibility.
*
* @see mavlink_finalize_message_chan
* @param msg Message to finalize
* @param system_id Id of the sending (this) system, 1-127
* @param length Message length, usually just the counter incremented while packing the message
*/
static inline uint16_t mavlink_finalize_message(mavlink_message_t* msg, uint8_t system_id, uint8_t component_id, uint16_t length)
{
// This code part is the same for all messages;
uint16_t checksum;
msg->len = length;
msg->sysid = system_id;
msg->compid = component_id;
// One sequence number per component
msg->seq = mavlink_get_channel_status(MAVLINK_COMM_0)->current_tx_seq;
mavlink_get_channel_status(MAVLINK_COMM_0)->current_tx_seq = mavlink_get_channel_status(MAVLINK_COMM_0)->current_tx_seq+1;
checksum = crc_calculate((uint8_t*)((void*)msg), length + MAVLINK_CORE_HEADER_LEN);
msg->ck_a = (uint8_t)(checksum & 0xFF); ///< High byte
msg->ck_b = (uint8_t)(checksum >> 8); ///< Low byte
return length + MAVLINK_NUM_NON_STX_PAYLOAD_BYTES;
}
/**
* @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, usually just the counter incremented while packing the message
*/
static inline uint16_t mavlink_finalize_message_chan(mavlink_message_t* msg, uint8_t system_id, uint8_t component_id, uint8_t chan, uint16_t length)
{
// This code part is the same for all messages;
uint16_t checksum;
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*)((void*)msg), length + MAVLINK_CORE_HEADER_LEN);
msg->ck_a = (uint8_t)(checksum & 0xFF); ///< High byte
msg->ck_b = (uint8_t)(checksum >> 8); ///< Low byte
return length + MAVLINK_NUM_NON_STX_PAYLOAD_BYTES;
}
/**
* @brief Pack a message to send it over a serial byte stream
*/
static inline uint16_t mavlink_msg_to_send_buffer(uint8_t* buffer, const mavlink_message_t* msg)
{
*(buffer+0) = MAVLINK_STX; ///< Start transmit
memcpy((buffer+1), msg, msg->len + MAVLINK_CORE_HEADER_LEN); ///< Core header plus payload
*(buffer + msg->len + MAVLINK_CORE_HEADER_LEN + 1) = msg->ck_a;
*(buffer + msg->len + MAVLINK_CORE_HEADER_LEN + 2) = msg->ck_b;
return msg->len + MAVLINK_NUM_NON_PAYLOAD_BYTES;
return 0;
}
/**
* @brief Get the required buffer size for this message
*/
static inline uint16_t mavlink_msg_get_send_buffer_length(const mavlink_message_t* msg)
{
return msg->len + MAVLINK_NUM_NON_PAYLOAD_BYTES;
}
union checksum_ {
uint16_t s;
uint8_t c[2];
};
union __mavlink_bitfield {
uint8_t uint8;
int8_t int8;
uint16_t uint16;
int16_t int16;
uint32_t uint32;
int32_t int32;
};
static inline void mavlink_start_checksum(mavlink_message_t* msg)
{
union checksum_ ck;
crc_init(&(ck.s));
msg->ck_a = ck.c[0];
msg->ck_b = ck.c[1];
}
static inline void mavlink_update_checksum(mavlink_message_t* msg, uint8_t c)
{
union checksum_ ck;
ck.c[0] = msg->ck_a;
ck.c[1] = msg->ck_b;
crc_accumulate(c, &(ck.s));
msg->ck_a = ck.c[0];
msg->ck_b = ck.c[1];
}
/**
* 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
*/
static inline uint8_t mavlink_parse_char(uint8_t chan, uint8_t c, mavlink_message_t* r_message, mavlink_status_t* r_mavlink_status)
{
static mavlink_message_t m_mavlink_message[MAVLINK_COMM_NUM_BUFFERS];
// Initializes only once, values keep unchanged after first initialization
mavlink_parse_state_initialize(mavlink_get_channel_status(chan));
mavlink_message_t* rxmsg = &m_mavlink_message[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;
mavlink_start_checksum(rxmsg);
}
break;
case MAVLINK_PARSE_STATE_GOT_STX:
if (status->msg_received)
{
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:
rxmsg->payload[status->packet_idx++] = 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 (c != rxmsg->ck_a)
{
// 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;
mavlink_start_checksum(rxmsg);
}
}
else
{
status->parse_state = MAVLINK_PARSE_STATE_GOT_CRC1;
}
break;
case MAVLINK_PARSE_STATE_GOT_CRC1:
if (c != rxmsg->ck_b)
{// 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;
mavlink_start_checksum(rxmsg);
}
}
else
{
// Successfully got message
status->msg_received = 1;
status->parse_state = MAVLINK_PARSE_STATE_IDLE;
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;
}
/**
* 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
*/
#define MAVLINK_PACKET_START_CANDIDATES 50
/*
static inline uint8_t mavlink_parse_char_new(uint8_t chan, uint8_t c, mavlink_message_t* r_message, mavlink_status_t* r_mavlink_status)
{
static mavlink_status_t m_mavlink_status[MAVLINK_COMM_NUM_BUFFERS];
static uint8_t m_msgbuf[MAVLINK_COMM_NUM_BUFFERS][MAVLINK_MAX_PACKET_LEN * 2];
static uint8_t m_msgbuf_index[MAVLINK_COMM_NUM_BUFFERS];
static mavlink_message_t m_mavlink_message[MAVLINK_COMM_NUM_BUFFERS];
static uint8_t m_packet_start[MAVLINK_COMM_NUM_BUFFERS][MAVLINK_PACKET_START_CANDIDATES];
static uint8_t m_packet_start_index_read[MAVLINK_COMM_NUM_BUFFERS];
static uint8_t m_packet_start_index_write[MAVLINK_COMM_NUM_BUFFERS];
// Set a packet start candidate index if sign is start sign
if (c == MAVLINK_STX)
{
m_packet_start[chan][++(m_packet_start_index_write[chan]) % MAVLINK_PACKET_START_CANDIDATES] = m_msgbuf_index[chan];
}
// Parse normally, if a CRC mismatch occurs retry with the next packet index
}
// static mavlink_status_t m_mavlink_status[MAVLINK_COMM_NUM_BUFFERS];
// static mavlink_message_t m_mavlink_message[MAVLINK_COMM_NUM_BUFFERS];
//// Initializes only once, values keep unchanged after first initialization
// mavlink_parse_state_initialize(&m_mavlink_status[chan]);
//
//mavlink_message_t* rxmsg = &m_mavlink_message[chan]; ///< The currently decoded message
//mavlink_status_t* status = &m_mavlink_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;
// mavlink_start_checksum(rxmsg);
// }
// break;
//
//case MAVLINK_PARSE_STATE_GOT_STX:
// if (status->msg_received)
// {
// 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:
// rxmsg->payload[status->packet_idx++] = 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 (c != rxmsg->ck_a)
// {
// // Check first checksum byte
// status->parse_error++;
// status->msg_received = 0;
// status->parse_state = MAVLINK_PARSE_STATE_IDLE;
// }
// else
// {
// status->parse_state = MAVLINK_PARSE_STATE_GOT_CRC1;
// }
// break;
//
//case MAVLINK_PARSE_STATE_GOT_CRC1:
// if (c != rxmsg->ck_b)
// {// Check second checksum byte
// status->parse_error++;
// status->msg_received = 0;
// status->parse_state = MAVLINK_PARSE_STATE_IDLE;
// }
// else
// {
// // Successfully got message
// status->msg_received = 1;
// status->parse_state = MAVLINK_PARSE_STATE_IDLE;
// 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_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_seq = status->current_seq+1;
r_mavlink_status->packet_rx_success_count = status->packet_rx_success_count;
r_mavlink_status->packet_rx_drop_count = status->parse_error;
return status->msg_received;
}
*/
typedef union __generic_16bit
{
uint8_t b[2];
int16_t s;
} generic_16bit;
typedef union __generic_32bit
{
uint8_t b[4];
float f;
int32_t i;
int16_t s;
} generic_32bit;
typedef union __generic_64bit
{
uint8_t b[8];
int64_t ll; ///< Long long (64 bit)
double d; ///< IEEE-754 double precision floating point
} generic_64bit;
/**
* @brief Place an unsigned byte into the buffer
*
* @param b the byte to add
* @param bindex the position in the packet
* @param buffer the packet buffer
* @return the new position of the last used byte in the buffer
*/
static inline uint8_t put_uint8_t_by_index(uint8_t b, uint8_t bindex, uint8_t* buffer)
{
*(buffer + bindex) = b;
return sizeof(b);
}
/**
* @brief Place a signed byte into the buffer
*
* @param b the byte to add
* @param bindex the position in the packet
* @param buffer the packet buffer
* @return the new position of the last used byte in the buffer
*/
static inline uint8_t put_int8_t_by_index(int8_t b, int8_t bindex, uint8_t* buffer)
{
*(buffer + bindex) = (uint8_t)b;
return sizeof(b);
}
/**
* @brief Place two unsigned bytes into the buffer
*
* @param b the bytes to add
* @param bindex the position in the packet
* @param buffer the packet buffer
* @return the new position of the last used byte in the buffer
*/
static inline uint8_t put_uint16_t_by_index(uint16_t b, const uint8_t bindex, uint8_t* buffer)
{
buffer[bindex] = (b>>8)&0xff;
buffer[bindex+1] = (b & 0xff);
return sizeof(b);
}
/**
* @brief Place two signed bytes into the buffer
*
* @param b the bytes to add
* @param bindex the position in the packet
* @param buffer the packet buffer
* @return the new position of the last used byte in the buffer
*/
static inline uint8_t put_int16_t_by_index(int16_t b, uint8_t bindex, uint8_t* buffer)
{
return put_uint16_t_by_index(b, bindex, buffer);
}
/**
* @brief Place four unsigned bytes into the buffer
*
* @param b the bytes to add
* @param bindex the position in the packet
* @param buffer the packet buffer
* @return the new position of the last used byte in the buffer
*/
static inline uint8_t put_uint32_t_by_index(uint32_t b, const uint8_t bindex, uint8_t* buffer)
{
buffer[bindex] = (b>>24)&0xff;
buffer[bindex+1] = (b>>16)&0xff;
buffer[bindex+2] = (b>>8)&0xff;
buffer[bindex+3] = (b & 0xff);
return sizeof(b);
}
/**
* @brief Place four signed bytes into the buffer
*
* @param b the bytes to add
* @param bindex the position in the packet
* @param buffer the packet buffer
* @return the new position of the last used byte in the buffer
*/
static inline uint8_t put_int32_t_by_index(int32_t b, uint8_t bindex, uint8_t* buffer)
{
buffer[bindex] = (b>>24)&0xff;
buffer[bindex+1] = (b>>16)&0xff;
buffer[bindex+2] = (b>>8)&0xff;
buffer[bindex+3] = (b & 0xff);
return sizeof(b);
}
/**
* @brief Place four unsigned bytes into the buffer
*
* @param b the bytes to add
* @param bindex the position in the packet
* @param buffer the packet buffer
* @return the new position of the last used byte in the buffer
*/
static inline uint8_t put_uint64_t_by_index(uint64_t b, const uint8_t bindex, uint8_t* buffer)
{
buffer[bindex] = (b>>56)&0xff;
buffer[bindex+1] = (b>>48)&0xff;
buffer[bindex+2] = (b>>40)&0xff;
buffer[bindex+3] = (b>>32)&0xff;
buffer[bindex+4] = (b>>24)&0xff;
buffer[bindex+5] = (b>>16)&0xff;
buffer[bindex+6] = (b>>8)&0xff;
buffer[bindex+7] = (b & 0xff);
return sizeof(b);
}
/**
* @brief Place four signed bytes into the buffer
*
* @param b the bytes to add
* @param bindex the position in the packet
* @param buffer the packet buffer
* @return the new position of the last used byte in the buffer
*/
static inline uint8_t put_int64_t_by_index(int64_t b, uint8_t bindex, uint8_t* buffer)
{
return put_uint64_t_by_index(b, bindex, buffer);
}
/**
* @brief Place a float into the buffer
*
* @param b the float to add
* @param bindex the position in the packet
* @param buffer the packet buffer
* @return the new position of the last used byte in the buffer
*/
static inline uint8_t put_float_by_index(float b, uint8_t bindex, uint8_t* buffer)
{
generic_32bit g;
g.f = b;
return put_int32_t_by_index(g.i, bindex, buffer);
}
/**
* @brief Place an array into the buffer
*
* @param b the array to add
* @param length size of the array (for strings: length WITH '\0' char)
* @param bindex the position in the packet
* @param buffer packet buffer
* @return new position of the last used byte in the buffer
*/
static inline uint8_t put_array_by_index(const int8_t* b, uint8_t length, uint8_t bindex, uint8_t* buffer)
{
memcpy(buffer+bindex, b, length);
return length;
}
/**
* @brief Place a string into the buffer
*
* @param b the string to add
* @param maxlength size of the array (for strings: length WITHOUT '\0' char)
* @param bindex the position in the packet
* @param buffer packet buffer
* @return new position of the last used byte in the buffer
*/
static inline uint8_t put_string_by_index(const char* b, uint8_t maxlength, uint8_t bindex, uint8_t* buffer)
{
uint16_t length = 0;
// Copy string into buffer, ensuring not to exceed the buffer size
int i;
for (i = 1; i < maxlength; i++)
{
length++;
// String characters
if (i < (maxlength - 1))
{
buffer[bindex+i] = b[i];
// Stop at null character
if (b[i] == '\0')
{
break;
}
}
// Enforce null termination at end of buffer
else if (i == (maxlength - 1))
{
buffer[i] = '\0';
}
}
// Write length into first field
put_uint8_t_by_index(length, bindex, buffer);
return length;
}
/**
* @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
*/
static inline 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
generic_32bit bin;
generic_32bit bout;
uint8_t i_bit_index, i_byte_index, curr_bits_n;
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];
// 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 <= (unsigned)(8 - i_bit_index))
{
// Enough space
curr_bits_n = 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) & bout.i);
// 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 a similar function
/*
#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);
}
}
*/
static inline void mavlink_send_uart_uint8_t(mavlink_channel_t chan, uint8_t b, uint16_t* checksum)
{
crc_accumulate(b, checksum);
comm_send_ch(chan, b);
}
static inline void mavlink_send_uart_int8_t(mavlink_channel_t chan, int8_t b, uint16_t* checksum)
{
crc_accumulate(b, checksum);
comm_send_ch(chan, b);
}
static inline void mavlink_send_uart_uint16_t(mavlink_channel_t chan, uint16_t b, uint16_t* checksum)
{
char s;
s = (b>>8)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b & 0xff);
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
}
static inline void mavlink_send_uart_int16_t(mavlink_channel_t chan, int16_t b, uint16_t* checksum)
{
mavlink_send_uart_uint16_t(chan, b, checksum);
}
static inline void mavlink_send_uart_uint32_t(mavlink_channel_t chan, uint32_t b, uint16_t* checksum)
{
char s;
s = (b>>24)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b>>16)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b>>8)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b & 0xff);
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
}
static inline void mavlink_send_uart_int32_t(mavlink_channel_t chan, int32_t b, uint16_t* checksum)
{
mavlink_send_uart_uint32_t(chan, b, checksum);
}
static inline void mavlink_send_uart_uint64_t(mavlink_channel_t chan, uint64_t b, uint16_t* checksum)
{
char s;
s = (b>>56)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b>>48)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b>>40)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b>>32)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b>>24)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b>>16)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b>>8)&0xff;
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
s = (b & 0xff);
comm_send_ch(chan, s);
crc_accumulate(s, checksum);
}
static inline void mavlink_send_uart_int64_t(mavlink_channel_t chan, int64_t b, uint16_t* checksum)
{
mavlink_send_uart_uint64_t(chan, b, checksum);
}
static inline void mavlink_send_uart_float(mavlink_channel_t chan, float b, uint16_t* checksum)
{
generic_32bit g;
g.f = b;
mavlink_send_uart_uint32_t(chan, g.i, checksum);
}
static inline void mavlink_send_uart_double(mavlink_channel_t chan, double b, uint16_t* checksum)
{
generic_64bit g;
g.d = b;
mavlink_send_uart_uint32_t(chan, g.ll, checksum);
}
static inline void mavlink_send_uart(mavlink_channel_t chan, mavlink_message_t* msg)
{
// ARM7 MCU board implementation
// Create pointer on message struct
// Send STX
comm_send_ch(chan, MAVLINK_STX);
comm_send_ch(chan, msg->len);
comm_send_ch(chan, msg->seq);
comm_send_ch(chan, msg->sysid);
comm_send_ch(chan, msg->compid);
comm_send_ch(chan, msg->msgid);
for(uint16_t i = 0; i < msg->len; i++)
{
comm_send_ch(chan, msg->payload[i]);
}
comm_send_ch(chan, msg->ck_a);
comm_send_ch(chan, msg->ck_b);
}
#endif
#endif /* _MAVLINK_PROTOCOL_H_ */
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