/
pprz_transport.c
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/
pprz_transport.c
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/*
* Copyright (C) 2006 Pascal Brisset, Antoine Drouin
* Copyright (C) 2014 Gautier Hattenberger <gautier.hattenberger@enac.fr>
*
* This file is part of paparazzi.
*
* paparazzi is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* paparazzi is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with paparazzi; see the file COPYING. If not, see
* <http://www.gnu.org/licenses/>.
*
*/
/**
* @file subsystems/datalink/pprz_transport.c
*
* Building and parsing Paparazzi frames.
*
* Pprz frame:
*
* |STX|length|... payload=(length-4) bytes ...|Checksum A|Checksum B|
*
* where checksum is computed over length and payload:
* @code
* ck_A = ck_B = length
* for each byte b in payload
* ck_A += b;
* ck_b += ck_A;
* @endcode
*/
#include <inttypes.h>
#include "subsystems/datalink/downlink.h"
#ifndef PPRZ_DATALINK_EXPORT
#include "subsystems/datalink/pprz_transport.h"
#else /* PPRZ_DATALINK_EXPORT defined */
#include "pprz_transport.h"
#endif
struct pprz_transport pprz_tp;
static void put_1byte(struct pprz_transport *trans, struct link_device *dev, const uint8_t byte)
{
trans->ck_a_tx += byte;
trans->ck_b_tx += trans->ck_a_tx;
dev->transmit(dev->periph, byte);
}
static void put_bytes(struct pprz_transport *trans, struct link_device *dev,
enum TransportDataType type __attribute__((unused)), enum TransportDataFormat format __attribute__((unused)),
uint8_t len, const void *bytes)
{
const uint8_t *b = (const uint8_t *) bytes;
int i;
for (i = 0; i < len; i++) {
put_1byte(trans, dev, b[i]);
}
}
static void put_named_byte(struct pprz_transport *trans, struct link_device *dev,
enum TransportDataType type __attribute__((unused)), enum TransportDataFormat format __attribute__((unused)),
uint8_t byte, const char *name __attribute__((unused)))
{
put_1byte(trans, dev, byte);
}
static uint8_t size_of(struct pprz_transport *trans __attribute__((unused)), uint8_t len)
{
// message length: payload + protocol overhead (STX + len + ck_a + ck_b = 4)
return len + 4;
}
static void start_message(struct pprz_transport *trans, struct link_device *dev, uint8_t payload_len)
{
downlink.nb_msgs++;
dev->transmit(dev->periph, STX);
const uint8_t msg_len = size_of(trans, payload_len);
dev->transmit(dev->periph, msg_len);
trans->ck_a_tx = msg_len;
trans->ck_b_tx = msg_len;
}
static void end_message(struct pprz_transport *trans, struct link_device *dev)
{
dev->transmit(dev->periph, trans->ck_a_tx);
dev->transmit(dev->periph, trans->ck_b_tx);
dev->send_message(dev->periph);
}
static void overrun(struct pprz_transport *trans __attribute__((unused)),
struct link_device *dev __attribute__((unused)))
{
downlink.nb_ovrn++;
}
static void count_bytes(struct pprz_transport *trans __attribute__((unused)),
struct link_device *dev __attribute__((unused)), uint8_t bytes)
{
downlink.nb_bytes += bytes;
}
static int check_available_space(struct pprz_transport *trans __attribute__((unused)), struct link_device *dev,
uint8_t bytes)
{
return dev->check_free_space(dev->periph, bytes);
}
void pprz_transport_init(struct pprz_transport *t)
{
t->status = UNINIT;
t->trans_rx.msg_received = FALSE;
t->trans_tx.size_of = (size_of_t) size_of;
t->trans_tx.check_available_space = (check_available_space_t) check_available_space;
t->trans_tx.put_bytes = (put_bytes_t) put_bytes;
t->trans_tx.put_named_byte = (put_named_byte_t) put_named_byte;
t->trans_tx.start_message = (start_message_t) start_message;
t->trans_tx.end_message = (end_message_t) end_message;
t->trans_tx.overrun = (overrun_t) overrun;
t->trans_tx.count_bytes = (count_bytes_t) count_bytes;
t->trans_tx.impl = (void *)(t);
}