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Paranoid PPM shape checking

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This commit is contained in:
Lorenz Meier 2013-12-27 12:02:57 +01:00
parent affc8ae910
commit db46672bc4
1 changed files with 10 additions and 9 deletions
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19
src/drivers/stm32/drv_hrt.c
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@ -1,6 +1,6 @@
/****************************************************************************
*
* Copyright (C) 2012 PX4 Development Team. All rights reserved.
* Copyright (c) 2012, 2013 PX4 Development Team. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@ -336,17 +336,18 @@ static void hrt_call_invoke(void);
/*
* PPM decoder tuning parameters
*/
# define PPM_MAX_PULSE_WIDTH 700 /* maximum width of a valid pulse */
# define PPM_MIN_PULSE_WIDTH 200 /* minimum width of a valid first pulse */
# define PPM_MAX_PULSE_WIDTH 600 /* maximum width of a valid first pulse */
# define PPM_MIN_CHANNEL_VALUE 800 /* shortest valid channel signal */
# define PPM_MAX_CHANNEL_VALUE 2200 /* longest valid channel signal */
# define PPM_MIN_START 2400 /* shortest valid start gap (only 2nd part of pulse) */
# define PPM_MAX_CHANNEL_VALUE 2200 /* longest valid channel signal */
# define PPM_MIN_START 2300 /* shortest valid start gap (only 2nd part of pulse) */
/* decoded PPM buffer */
#define PPM_MIN_CHANNELS 5
#define PPM_MAX_CHANNELS 20
/* Number of same-sized frames required to 'lock' */
#define PPM_CHANNEL_LOCK 4 /* should be less than the input timeout */
#define PPM_CHANNEL_LOCK 4 /* should be less than the input timeout */
__EXPORT uint16_t ppm_buffer[PPM_MAX_CHANNELS];
__EXPORT uint16_t ppm_frame_length = 0;
@ -518,8 +519,8 @@ hrt_ppm_decode(uint32_t status)
case ARM:
/* we expect a pulse giving us the first mark */
if (width > PPM_MAX_PULSE_WIDTH)
goto error; /* pulse was too long */
if (width < PPM_MIN_PULSE_WIDTH || width > PPM_MAX_PULSE_WIDTH)
goto error; /* pulse was too short or too long */
/* record the mark timing, expect an inactive edge */
ppm.last_mark = ppm.last_edge;
@ -533,8 +534,8 @@ hrt_ppm_decode(uint32_t status)
case INACTIVE:
/* we expect a short pulse */
if (width > PPM_MAX_PULSE_WIDTH)
goto error; /* pulse was too long */
if (width < PPM_MIN_PULSE_WIDTH || width > PPM_MAX_PULSE_WIDTH)
goto error; /* pulse was too short or too long */
/* this edge is not interesting, but now we are ready for the next mark */
ppm.phase = ACTIVE;