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LibrePilot/flight/pios/common/pios_sbus.c

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/**
******************************************************************************
* @addtogroup PIOS PIOS Core hardware abstraction layer
* @{
* @addtogroup PIOS_SBus Futaba S.Bus receiver functions
* @brief Code to read Futaba S.Bus receiver serial stream
* @{
*
* @file pios_sbus.c
* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2011.
* @brief Code to read Futaba S.Bus receiver serial stream
* @see The GNU Public License (GPL) Version 3
*
*****************************************************************************/
/*
* This program 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 3 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include "pios.h"
#ifdef PIOS_INCLUDE_SBUS
#include "pios_sbus_priv.h"
/* Forward Declarations */
static int32_t PIOS_SBus_Get(uint32_t rcvr_id, uint8_t channel);
static uint16_t PIOS_SBus_RxInCallback(uint32_t context,
uint8_t *buf,
uint16_t buf_len,
uint16_t *headroom,
bool *need_yield);
static void PIOS_SBus_Supervisor(uint32_t sbus_id);
/* Local Variables */
const struct pios_rcvr_driver pios_sbus_rcvr_driver = {
.read = PIOS_SBus_Get,
};
enum pios_sbus_dev_magic {
PIOS_SBUS_DEV_MAGIC = 0x53427573,
};
struct pios_sbus_state {
uint16_t channel_data[PIOS_SBUS_NUM_INPUTS];
uint8_t received_data[SBUS_FRAME_LENGTH - 2];
uint8_t receive_timer;
uint8_t failsafe_timer;
uint8_t frame_found;
uint8_t byte_count;
};
struct pios_sbus_dev {
enum pios_sbus_dev_magic magic;
const struct pios_sbus_cfg *cfg;
struct pios_sbus_state state;
};
/* Allocate S.Bus device descriptor */
#if defined(PIOS_INCLUDE_FREERTOS)
static struct pios_sbus_dev *PIOS_SBus_Alloc(void)
{
struct pios_sbus_dev *sbus_dev;
sbus_dev = (struct pios_sbus_dev *)pios_malloc(sizeof(*sbus_dev));
if (!sbus_dev) {
return NULL;
}
sbus_dev->magic = PIOS_SBUS_DEV_MAGIC;
return sbus_dev;
}
#else
static struct pios_sbus_dev pios_sbus_devs[PIOS_SBUS_MAX_DEVS];
static uint8_t pios_sbus_num_devs;
static struct pios_sbus_dev *PIOS_SBus_Alloc(void)
{
struct pios_sbus_dev *sbus_dev;
if (pios_sbus_num_devs >= PIOS_SBUS_MAX_DEVS) {
return NULL;
}
sbus_dev = &pios_sbus_devs[pios_sbus_num_devs++];
sbus_dev->magic = PIOS_SBUS_DEV_MAGIC;
return sbus_dev;
}
#endif /* if defined(PIOS_INCLUDE_FREERTOS) */
/* Validate S.Bus device descriptor */
static bool PIOS_SBus_Validate(struct pios_sbus_dev *sbus_dev)
{
return sbus_dev->magic == PIOS_SBUS_DEV_MAGIC;
}
/* Reset channels in case of lost signal or explicit failsafe receiver flag */
static void PIOS_SBus_ResetChannels(struct pios_sbus_state *state)
{
for (int i = 0; i < PIOS_SBUS_NUM_INPUTS; i++) {
state->channel_data[i] = PIOS_RCVR_TIMEOUT;
}
}
/* Reset S.Bus receiver state */
static void PIOS_SBus_ResetState(struct pios_sbus_state *state)
{
state->receive_timer = 0;
state->failsafe_timer = 0;
state->frame_found = 0;
PIOS_SBus_ResetChannels(state);
}
/* Initialise S.Bus receiver interface */
int32_t PIOS_SBus_Init(uint32_t *sbus_id,
const struct pios_sbus_cfg *cfg,
const struct pios_com_driver *driver,
uint32_t lower_id)
{
PIOS_DEBUG_Assert(sbus_id);
PIOS_DEBUG_Assert(cfg);
PIOS_DEBUG_Assert(driver);
struct pios_sbus_dev *sbus_dev;
sbus_dev = (struct pios_sbus_dev *)PIOS_SBus_Alloc();
if (!sbus_dev) {
goto out_fail;
}
/* Bind the configuration to the device instance */
sbus_dev->cfg = cfg;
PIOS_SBus_ResetState(&(sbus_dev->state));
*sbus_id = (uint32_t)sbus_dev;
/* Enable inverter clock and enable the inverter */
(*cfg->gpio_clk_func)(cfg->gpio_clk_periph, ENABLE);
GPIO_Init(cfg->inv.gpio, &cfg->inv.init);
GPIO_WriteBit(cfg->inv.gpio, cfg->inv.init.GPIO_Pin, cfg->gpio_inv_enable);
/* Set comm driver callback */
(driver->bind_rx_cb)(lower_id, PIOS_SBus_RxInCallback, *sbus_id);
if (!PIOS_RTC_RegisterTickCallback(PIOS_SBus_Supervisor, *sbus_id)) {
PIOS_DEBUG_Assert(0);
}
return 0;
out_fail:
return -1;
}
/**
* Get the value of an input channel
* \param[in] channel Number of the channel desired (zero based)
* \output PIOS_RCVR_INVALID channel not available
* \output PIOS_RCVR_TIMEOUT failsafe condition or missing receiver
* \output >=0 channel value
*/
static int32_t PIOS_SBus_Get(uint32_t rcvr_id, uint8_t channel)
{
struct pios_sbus_dev *sbus_dev = (struct pios_sbus_dev *)rcvr_id;
if (!PIOS_SBus_Validate(sbus_dev)) {
return PIOS_RCVR_INVALID;
}
/* return error if channel is not available */
if (channel >= PIOS_SBUS_NUM_INPUTS) {
return PIOS_RCVR_INVALID;
}
return sbus_dev->state.channel_data[channel];
}
/**
* Compute channel_data[] from received_data[].
* For efficiency it unrolls first 8 channels without loops and does the
* same for other 8 channels. Also 2 discrete channels will be set.
*/
static void PIOS_SBus_UnrollChannels(struct pios_sbus_state *state)
{
uint8_t *s = state->received_data;
uint16_t *d = state->channel_data;
#define F(v, s) (((v) >> (s)) & 0x7ff)
/* unroll channels 1-8 */
*d++ = F(s[0] | s[1] << 8, 0);
*d++ = F(s[1] | s[2] << 8, 3);
*d++ = F(s[2] | s[3] << 8 | s[4] << 16, 6);
*d++ = F(s[4] | s[5] << 8, 1);
*d++ = F(s[5] | s[6] << 8, 4);
*d++ = F(s[6] | s[7] << 8 | s[8] << 16, 7);
*d++ = F(s[8] | s[9] << 8, 2);
*d++ = F(s[9] | s[10] << 8, 5);
/* unroll channels 9-16 */
*d++ = F(s[11] | s[12] << 8, 0);
*d++ = F(s[12] | s[13] << 8, 3);
*d++ = F(s[13] | s[14] << 8 | s[15] << 16, 6);
*d++ = F(s[15] | s[16] << 8, 1);
*d++ = F(s[16] | s[17] << 8, 4);
*d++ = F(s[17] | s[18] << 8 | s[19] << 16, 7);
*d++ = F(s[19] | s[20] << 8, 2);
*d++ = F(s[20] | s[21] << 8, 5);
/* unroll discrete channels 17 and 18 */
*d++ = (s[22] & SBUS_FLAG_DC1) ? SBUS_VALUE_MAX : SBUS_VALUE_MIN;
*d++ = (s[22] & SBUS_FLAG_DC2) ? SBUS_VALUE_MAX : SBUS_VALUE_MIN;
}
/* Update decoder state processing input byte from the S.Bus stream */
static void PIOS_SBus_UpdateState(struct pios_sbus_state *state, uint8_t b)
{
/* should not process any data until new frame is found */
if (!state->frame_found) {
return;
}
if (state->byte_count == 0) {
if (b != SBUS_SOF_BYTE) {
/* discard the whole frame if the 1st byte is not correct */
state->frame_found = 0;
} else {
/* do not store the SOF byte */
state->byte_count++;
}
return;
}
/* do not store last frame byte as well */
if (state->byte_count < SBUS_FRAME_LENGTH - 1) {
/* store next byte */
state->received_data[state->byte_count - 1] = b;
state->byte_count++;
} else {
if (b == SBUS_EOF_BYTE || (b % SBUS_R7008SB_EOF_COUNTER_MASK) == SBUS_R7008SB_EOF_BYTE) {
/* full frame received */
uint8_t flags = state->received_data[SBUS_FRAME_LENGTH - 3];
if (flags & SBUS_FLAG_FL) {
/* frame lost, do not update */
} else if (flags & SBUS_FLAG_FS) {
/* failsafe flag active */
PIOS_SBus_ResetChannels(state);
} else {
/* data looking good */
PIOS_SBus_UnrollChannels(state);
state->failsafe_timer = 0;
}
} else {
/* discard whole frame */
}
/* prepare for the next frame */
state->frame_found = 0;
}
}
/* Comm byte received callback */
static uint16_t PIOS_SBus_RxInCallback(uint32_t context,
uint8_t *buf,
uint16_t buf_len,
uint16_t *headroom,
bool *need_yield)
{
struct pios_sbus_dev *sbus_dev = (struct pios_sbus_dev *)context;
bool valid = PIOS_SBus_Validate(sbus_dev);
PIOS_Assert(valid);
struct pios_sbus_state *state = &(sbus_dev->state);
/* process byte(s) and clear receive timer */
for (uint8_t i = 0; i < buf_len; i++) {
PIOS_SBus_UpdateState(state, buf[i]);
state->receive_timer = 0;
}
/* Always signal that we can accept another byte */
if (headroom) {
*headroom = SBUS_FRAME_LENGTH;
}
/* We never need a yield */
*need_yield = false;
/* Always indicate that all bytes were consumed */
return buf_len;
}
/**
* Input data supervisor is called periodically and provides
* two functions: frame syncing and failsafe triggering.
*
* S.Bus frames come at 7ms (HS) or 14ms (FS) rate at 100000bps.
* RTC timer is running at 625Hz (1.6ms). So with divider 2 it gives
* 3.2ms pause between frames which is good for both S.Bus frame rates.
*
* Data receive function must clear the receive_timer to confirm new
* data reception. If no new data received in 100ms, we must call the
* failsafe function which clears all channels.
*/
static void PIOS_SBus_Supervisor(uint32_t sbus_id)
{
struct pios_sbus_dev *sbus_dev = (struct pios_sbus_dev *)sbus_id;
bool valid = PIOS_SBus_Validate(sbus_dev);
PIOS_Assert(valid);
struct pios_sbus_state *state = &(sbus_dev->state);
/* waiting for new frame if no bytes were received in 3.2ms */
if (++state->receive_timer > 2) {
state->frame_found = 1;
state->byte_count = 0;
state->receive_timer = 0;
}
/* activate failsafe if no frames have arrived in 102.4ms */
if (++state->failsafe_timer > 64) {
PIOS_SBus_ResetChannels(state);
state->failsafe_timer = 0;
}
}
#endif /* PIOS_INCLUDE_SBUS */
/**
* @}
* @}
*/