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| author | Holger Steinhaus L <hsteinhaus@gmx.de> | 2013-11-11 12:14:03 +0100 |
|---|---|---|
| committer | Lorenz Meier <lm@inf.ethz.ch> | 2013-12-13 17:30:14 +0100 |
| commit | 3a40ea8338206b247aadb40e3709a22e0699135b (patch) | |
| tree | 63740e1b646135e007a31f775b0830d7ce443595 /src | |
| parent | 0b9b68f0d96f59c9cd406547ee52fb52617a298f (diff) | |
| download | px4-firmware-3a40ea8338206b247aadb40e3709a22e0699135b.tar.gz px4-firmware-3a40ea8338206b247aadb40e3709a22e0699135b.tar.bz2 px4-firmware-3a40ea8338206b247aadb40e3709a22e0699135b.zip | |
more precise range conversion for SBus input signals
Diffstat (limited to 'src')
| -rw-r--r-- | src/modules/px4iofirmware/sbus.c | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/src/modules/px4iofirmware/sbus.c b/src/modules/px4iofirmware/sbus.c index c523df6ca..8034e7077 100644 --- a/src/modules/px4iofirmware/sbus.c +++ b/src/modules/px4iofirmware/sbus.c @@ -55,6 +55,24 @@ #define SBUS_FRAME_SIZE 25 #define SBUS_INPUT_CHANNELS 16 +/* + Measured values with Futaba FX-30/R6108SB: + -+100% on TX: PCM 1.100/1.520/1.950ms -> SBus raw values: 350/1024/1700 (100% ATV) + -+140% on TX: PCM 0.930/1.520/2.112ms -> SBus raw values: 78/1024/1964 (140% ATV) + -+152% on TX: PCM 0.884/1.520/2.160ms -> SBus raw values: 1/1024/2047 (140% ATV plus dirty tricks) +*/ + +/* define range mapping here, -+100% -> 1000..2000 */ +#define SBUS_RANGE_MIN 350.0f +#define SBUS_RANGE_MAX 1700.0f + +#define SBUS_TARGET_MIN 1000.0f +#define SBUS_TARGET_MAX 2000.0f + +/* pre-calculate the floating point stuff as far as possible at compile time */ +#define SBUS_SCALE_FACTOR ((SBUS_TARGET_MAX - SBUS_TARGET_MIN) / (SBUS_RANGE_MAX - SBUS_RANGE_MIN)) +#define SBUS_SCALE_OFFSET (int)(SBUS_TARGET_MIN - (SBUS_SCALE_FACTOR * SBUS_RANGE_MIN + 0.5f)) + static int sbus_fd = -1; static hrt_abstime last_rx_time; @@ -234,8 +252,9 @@ sbus_decode(hrt_abstime frame_time, uint16_t *values, uint16_t *num_values, uint } } - /* convert 0-2048 values to 1000-2000 ppm encoding in a very sloppy fashion */ - values[channel] = (value / 2) + 998; + + /* convert 0-2048 values to 1000-2000 ppm encoding in a not too sloppy fashion */ + values[channel] = (uint16_t)(value * SBUS_SCALE_FACTOR +.5f) + SBUS_SCALE_OFFSET; } /* decode switch channels if data fields are wide enough */ |