jlecoeur
commented
9 years ago Here is what PX4 is using
/****************************************************************************
*
* Copyright (c) 2012-2014 PX4 Development Team. All rights reserved.
*
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* modification, are permitted provided that the following conditions
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*
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* distribution.
* 3. Neither the name PX4 nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
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****************************************************************************/
/**
* @file dsm.c
*
* Serial protocol decoder for the Spektrum DSM* family of protocols.
*
* Decodes into the global PPM buffer and updates accordingly.
*/
#include <nuttx/config.h>
#include <nuttx/arch.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
#include <drivers/drv_hrt.h>
#include "px4io.h"
#define DSM_FRAME_SIZE 16 /**<DSM frame size in bytes*/
#define DSM_FRAME_CHANNELS 7 /**<Max supported DSM channels*/
static int dsm_fd = -1; /**< File handle to the DSM UART */
static hrt_abstime dsm_last_rx_time; /**< Timestamp when we last received */
static hrt_abstime dsm_last_frame_time; /**< Timestamp for start of last dsm frame */
static uint8_t dsm_frame[DSM_FRAME_SIZE]; /**< DSM dsm frame receive buffer */
static unsigned dsm_partial_frame_count; /**< Count of bytes received for current dsm frame */
static unsigned dsm_channel_shift; /**< Channel resolution, 0=unknown, 1=10 bit, 2=11 bit */
static unsigned dsm_frame_drops; /**< Count of incomplete DSM frames */
/**
* Attempt to decode a single channel raw channel datum
*
* The DSM* protocol doesn't provide any explicit framing,
* so we detect dsm frame boundaries by the inter-dsm frame delay.
*
* The minimum dsm frame spacing is 11ms; with 16 bytes at 115200bps
* dsm frame transmission time is ~1.4ms.
*
* We expect to only be called when bytes arrive for processing,
* and if an interval of more than 5ms passes between calls,
* the first byte we read will be the first byte of a dsm frame.
*
* In the case where byte(s) are dropped from a dsm frame, this also
* provides a degree of protection. Of course, it would be better
* if we didn't drop bytes...
*
* Upon receiving a full dsm frame we attempt to decode it
*
* @param[in] raw 16 bit raw channel value from dsm frame
* @param[in] shift position of channel number in raw data
* @param[out] channel pointer to returned channel number
* @param[out] value pointer to returned channel value
* @return true=raw value successfully decoded
*/
static bool
dsm_decode_channel(uint16_t raw, unsigned shift, unsigned *channel, unsigned *value)
{
if (raw == 0xffff)
return false;
*channel = (raw >> shift) & 0xf;
uint16_t data_mask = (1 << shift) - 1;
*value = raw & data_mask;
//debug("DSM: %d 0x%04x -> %d %d", shift, raw, *channel, *value);
return true;
}
/**
* Attempt to guess if receiving 10 or 11 bit channel values
*
* @param[in] reset true=reset the 10/11 bit state to unknown
*/
static void
dsm_guess_format(bool reset)
{
static uint32_t cs10;
static uint32_t cs11;
static unsigned samples;
/* reset the 10/11 bit sniffed channel masks */
if (reset) {
cs10 = 0;
cs11 = 0;
samples = 0;
dsm_channel_shift = 0;
return;
}
/* scan the channels in the current dsm_frame in both 10- and 11-bit mode */
for (unsigned i = 0; i < DSM_FRAME_CHANNELS; i++) {
uint8_t *dp = &dsm_frame[2 + (2 * i)];
uint16_t raw = (dp[0] << 8) | dp[1];
unsigned channel, value;
/* if the channel decodes, remember the assigned number */
if (dsm_decode_channel(raw, 10, &channel, &value) && (channel < 31))
cs10 |= (1 << channel);
if (dsm_decode_channel(raw, 11, &channel, &value) && (channel < 31))
cs11 |= (1 << channel);
/* XXX if we cared, we could look for the phase bit here to decide 1 vs. 2-dsm_frame format */
}
/* wait until we have seen plenty of frames - 5 should normally be enough */
if (samples++ < 5)
return;
/*
* Iterate the set of sensible sniffed channel sets and see whether
* decoding in 10 or 11-bit mode has yielded anything we recognize.
*
* XXX Note that due to what seem to be bugs in the DSM2 high-resolution
* stream, we may want to sniff for longer in some cases when we think we
* are talking to a DSM2 receiver in high-resolution mode (so that we can
* reject it, ideally).
* See e.g. http://git.openpilot.org/cru/OPReview-116 for a discussion
* of this issue.
*/
static uint32_t masks[] = {
0x3f, /* 6 channels (DX6) */
0x7f, /* 7 channels (DX7) */
0xff, /* 8 channels (DX8) */
0x1ff, /* 9 channels (DX9, etc.) */
0x3ff, /* 10 channels (DX10) */
0x1fff, /* 13 channels (DX10t) */
0x3fff /* 18 channels (DX10) */
};
unsigned votes10 = 0;
unsigned votes11 = 0;
for (unsigned i = 0; i < (sizeof(masks) / sizeof(masks[0])); i++) {
if (cs10 == masks[i])
votes10++;
if (cs11 == masks[i])
votes11++;
}
if ((votes11 == 1) && (votes10 == 0)) {
dsm_channel_shift = 11;
debug("DSM: 11-bit format");
return;
}
if ((votes10 == 1) && (votes11 == 0)) {
dsm_channel_shift = 10;
debug("DSM: 10-bit format");
return;
}
/* call ourselves to reset our state ... we have to try again */
debug("DSM: format detect fail, 10: 0x%08x %d 11: 0x%08x %d", cs10, votes10, cs11, votes11);
dsm_guess_format(true);
}
/**
* Initialize the DSM receive functionality
*
* Open the UART for receiving DSM frames and configure it appropriately
*
* @param[in] device Device name of DSM UART
*/
int
dsm_init(const char *device)
{
#ifdef CONFIG_ARCH_BOARD_PX4IO_V2
// enable power on DSM connector
POWER_SPEKTRUM(true);
#endif
if (dsm_fd < 0)
dsm_fd = open(device, O_RDONLY | O_NONBLOCK);
if (dsm_fd >= 0) {
struct termios t;
/* 115200bps, no parity, one stop bit */
tcgetattr(dsm_fd, &t);
cfsetspeed(&t, 115200);
t.c_cflag &= ~(CSTOPB | PARENB);
tcsetattr(dsm_fd, TCSANOW, &t);
/* initialise the decoder */
dsm_partial_frame_count = 0;
dsm_last_rx_time = hrt_absolute_time();
/* reset the format detector */
dsm_guess_format(true);
debug("DSM: ready");
} else {
debug("DSM: open failed");
}
return dsm_fd;
}
/**
* Handle DSM satellite receiver bind mode handler
*
* @param[in] cmd commands - dsm_bind_power_down, dsm_bind_power_up, dsm_bind_set_rx_out, dsm_bind_send_pulses, dsm_bind_reinit_uart
* @param[in] pulses Number of pulses for dsm_bind_send_pulses command
*/
void
dsm_bind(uint16_t cmd, int pulses)
{
#if !defined(CONFIG_ARCH_BOARD_PX4IO_V1) && !defined(CONFIG_ARCH_BOARD_PX4IO_V2)
#warning DSM BIND NOT IMPLEMENTED ON UNKNOWN PLATFORM
#else
const uint32_t usart1RxAsOutp =
GPIO_OUTPUT | GPIO_CNF_OUTPP | GPIO_MODE_50MHz | GPIO_OUTPUT_SET | GPIO_PORTA | GPIO_PIN10;
if (dsm_fd < 0)
return;
switch (cmd) {
case dsm_bind_power_down:
/*power down DSM satellite*/
#ifdef CONFIG_ARCH_BOARD_PX4IO_V1
POWER_RELAY1(0);
#else /* CONFIG_ARCH_BOARD_PX4IO_V2 */
POWER_SPEKTRUM(0);
#endif
break;
case dsm_bind_power_up:
/*power up DSM satellite*/
#ifdef CONFIG_ARCH_BOARD_PX4IO_V1
POWER_RELAY1(1);
#else /* CONFIG_ARCH_BOARD_PX4IO_V2 */
POWER_SPEKTRUM(1);
#endif
dsm_guess_format(true);
break;
case dsm_bind_set_rx_out:
/*Set UART RX pin to active output mode*/
stm32_configgpio(usart1RxAsOutp);
break;
case dsm_bind_send_pulses:
/*Pulse RX pin a number of times*/
for (int i = 0; i < pulses; i++) {
up_udelay(25);
stm32_gpiowrite(usart1RxAsOutp, false);
up_udelay(25);
stm32_gpiowrite(usart1RxAsOutp, true);
}
break;
case dsm_bind_reinit_uart:
/*Restore USART RX pin to RS232 receive mode*/
stm32_configgpio(GPIO_USART1_RX);
break;
}
#endif
}
/**
* Decode the entire dsm frame (all contained channels)
*
* @param[in] frame_time timestamp when this dsm frame was received. Used to detect RX loss in order to reset 10/11 bit guess.
* @param[out] values pointer to per channel array of decoded values
* @param[out] num_values pointer to number of raw channel values returned
* @return true=DSM frame successfully decoded, false=no update
*/
static bool
dsm_decode(hrt_abstime frame_time, uint16_t *values, uint16_t *num_values)
{
/*
debug("DSM dsm_frame %02x%02x %02x%02x %02x%02x %02x%02x %02x%02x %02x%02x %02x%02x %02x%02x",
dsm_frame[0], dsm_frame[1], dsm_frame[2], dsm_frame[3], dsm_frame[4], dsm_frame[5], dsm_frame[6], dsm_frame[7],
dsm_frame[8], dsm_frame[9], dsm_frame[10], dsm_frame[11], dsm_frame[12], dsm_frame[13], dsm_frame[14], dsm_frame[15]);
*/
/*
* If we have lost signal for at least a second, reset the
* format guessing heuristic.
*/
if (((frame_time - dsm_last_frame_time) > 1000000) && (dsm_channel_shift != 0))
dsm_guess_format(true);
/* we have received something we think is a dsm_frame */
dsm_last_frame_time = frame_time;
/* if we don't know the dsm_frame format, update the guessing state machine */
if (dsm_channel_shift == 0) {
dsm_guess_format(false);
return false;
}
/*
* The encoding of the first two bytes is uncertain, so we're
* going to ignore them for now.
*
* Each channel is a 16-bit unsigned value containing either a 10-
* or 11-bit channel value and a 4-bit channel number, shifted
* either 10 or 11 bits. The MSB may also be set to indicate the
* second dsm_frame in variants of the protocol where more than
* seven channels are being transmitted.
*/
for (unsigned i = 0; i < DSM_FRAME_CHANNELS; i++) {
uint8_t *dp = &dsm_frame[2 + (2 * i)];
uint16_t raw = (dp[0] << 8) | dp[1];
unsigned channel, value;
if (!dsm_decode_channel(raw, dsm_channel_shift, &channel, &value))
continue;
/* ignore channels out of range */
if (channel >= PX4IO_RC_INPUT_CHANNELS)
continue;
/* update the decoded channel count */
if (channel >= *num_values)
*num_values = channel + 1;
/* convert 0-1024 / 0-2048 values to 1000-2000 ppm encoding. */
if (dsm_channel_shift == 10)
value *= 2;
/*
* Spektrum scaling is special. There are these basic considerations
*
* * Midpoint is 1520 us
* * 100% travel channels are +- 400 us
*
* We obey the original Spektrum scaling (so a default setup will scale from
* 1100 - 1900 us), but we do not obey the weird 1520 us center point
* and instead (correctly) center the center around 1500 us. This is in order
* to get something useful without requiring the user to calibrate on a digital
* link for no reason.
*/
/* scaled integer for decent accuracy while staying efficient */
value = ((((int)value - 1024) * 1000) / 1700) + 1500;
/*
* Store the decoded channel into the R/C input buffer, taking into
* account the different ideas about channel assignement that we have.
*
* Specifically, the first four channels in rc_channel_data are roll, pitch, thrust, yaw,
* but the first four channels from the DSM receiver are thrust, roll, pitch, yaw.
*/
switch (channel) {
case 0:
channel = 2;
break;
case 1:
channel = 0;
break;
case 2:
channel = 1;
default:
break;
}
values[channel] = value;
}
/*
* Spektrum likes to send junk in higher channel numbers to fill
* their packets. We don't know about a 13 channel model in their TX
* lines, so if we get a channel count of 13, we'll return 12 (the last
* data index that is stable).
*/
if (*num_values == 13)
*num_values = 12;
if (dsm_channel_shift == 11) {
/* Set the 11-bit data indicator */
*num_values |= 0x8000;
}
/*
* XXX Note that we may be in failsafe here; we need to work out how to detect that.
*/
return true;
}
/**
* Called periodically to check for input data from the DSM UART
*
* The DSM* protocol doesn't provide any explicit framing,
* so we detect dsm frame boundaries by the inter-dsm frame delay.
* The minimum dsm frame spacing is 11ms; with 16 bytes at 115200bps
* dsm frame transmission time is ~1.4ms.
* We expect to only be called when bytes arrive for processing,
* and if an interval of more than 5ms passes between calls,
* the first byte we read will be the first byte of a dsm frame.
* In the case where byte(s) are dropped from a dsm frame, this also
* provides a degree of protection. Of course, it would be better
* if we didn't drop bytes...
* Upon receiving a full dsm frame we attempt to decode it.
*
* @param[out] values pointer to per channel array of decoded values
* @param[out] num_values pointer to number of raw channel values returned, high order bit 0:10 bit data, 1:11 bit data
* @return true=decoded raw channel values updated, false=no update
*/
bool
dsm_input(uint16_t *values, uint16_t *num_values)
{
ssize_t ret;
hrt_abstime now;
/*
*/
now = hrt_absolute_time();
if ((now - dsm_last_rx_time) > 5000) {
if (dsm_partial_frame_count > 0) {
dsm_frame_drops++;
dsm_partial_frame_count = 0;
}
}
/*
* Fetch bytes, but no more than we would need to complete
* the current dsm frame.
*/
ret = read(dsm_fd, &dsm_frame[dsm_partial_frame_count], DSM_FRAME_SIZE - dsm_partial_frame_count);
/* if the read failed for any reason, just give up here */
if (ret < 1)
return false;
dsm_last_rx_time = now;
/*
* Add bytes to the current dsm frame
*/
dsm_partial_frame_count += ret;
/*
* If we don't have a full dsm frame, return
*/
if (dsm_partial_frame_count < DSM_FRAME_SIZE)
return false;
/*
* Great, it looks like we might have a dsm frame. Go ahead and
* decode it.
*/
dsm_partial_frame_count = 0;
return dsm_decode(now, values, num_values);
}
GregoireH
We are currently limited to 7 channels for spektrum satellites. Implementing the DSMX protocol should fix this