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Solving correct Bearing Angle in ADSB TX app

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This commit is contained in:
Brumi-2021 2023-01-01 23:23:06 +01:00
parent c0f368c978
commit 2902365b80
2 changed files with 15 additions and 7 deletions
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20
firmware/common/adsb.cpp
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@ -311,18 +311,26 @@ void encode_frame_velo(ADSBFrame& frame, const uint32_t ICAO_address, const uint
uint32_t velo_ew_abs, velo_ns_abs, v_rate_coded_abs;
// To get NS and EW speeds from speed and bearing, a polar to cartesian conversion is enough
velo_ew = static_cast<int32_t>(sin_f32(DEG_TO_RAD(angle) + (pi / 2)) * speed);
velo_ns = static_cast<int32_t>(sin_f32(DEG_TO_RAD(angle)) * speed);
velo_ew = static_cast<int32_t>(sin_f32(DEG_TO_RAD(angle) ) * speed); // East direction, is the projection from West -> East is directly sin(angle=Compas Bearing) , (90º is the max +1, EAST) max velo_EW
velo_ns = static_cast<int32_t>(sin_f32( (pi/2 - DEG_TO_RAD(angle) ) ) * speed); // North direction,is the projection of North = cos(angle=Compas Bearing), cos(angle)= sen(90-angle) (0º is the max +1 NORTH) max velo_NS
v_rate_coded = (v_rate / 64) + 1;
v_rate_coded = (v_rate / 64) + 1; //encoding vertical rate source. (Decoding, VR ft/min = (Decimal v_rate_value - 1)* 64)
velo_ew_abs = abs(velo_ew) + 1;
velo_ns_abs = abs(velo_ns) + 1;
velo_ew_abs = abs(velo_ew) + 1; // encoding Velo speed EW , when sign Direction is 0 (+): West->East, (-) 1: East->West
velo_ns_abs = abs(velo_ns) + 1; // encoding Velo speed NS , when sign Direction is 0 (+): South->North , (-) 1: North->South
v_rate_coded_abs = abs(v_rate_coded);
make_frame_adsb(frame, ICAO_address);
frame.push_byte((TC_AIRBORNE_VELO << 3) | 1); // Subtype: 1 (subsonic)
// Airborne velocities are all transmitted with Type Code 19 ( TC=19, using 5 bits ,TC=19 [Binary: 10011]), the following 3 bits are Subt-type Code ,SC= 1,2,3,4
// SC Subtypes code 1 and 2 are used to report ground speeds of aircraft. (SC 3,4 to used to report true airspeed. SC 2,4 are for supersonic aircraft (not used in commercial airline).
frame.push_byte((TC_AIRBORNE_VELO << 3) | 1); // 1st byte , top 5 bits Type Code TC=19, and lower 3 bits (38-40 bits), SC=001 Subtype Code SC: 1 (subsonic) ,
// Message A, (ME bits from 14-35) , 22 bits = Sign ew(1 bit) + V_ew (10 bits) + Sign_ns (1 bit) + V_ns (10 bits)
// Vertical rate source bit VrSrc (ME bit 36) indicates source of the altitude measurements. GNSS altitude(0) / , barometric altitude(1).
// Vertical rate source direction,(ME bit 37) movement can be read from Svr bit , with 0 and 1 referring to climb and descent, respectively (ft/min)
// The encoded vertical rate value VR can be computed using message (ME bits 38 to 46). If the 9-bit block contains all zeros, the vertical rate information is not available.
// + Sign VrSrc (vert rate src) (1 bit)+ VrSrc (9 bits).
frame.push_byte(((velo_ew < 0 ? 1 : 0) << 2) | (velo_ew_abs >> 8));
frame.push_byte(velo_ew_abs);
frame.push_byte(((velo_ns < 0 ? 1 : 0) << 7) | (velo_ns_abs >> 3));

2
firmware/common/sine_table.hpp
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@ -37,7 +37,7 @@ print(v)
*/
constexpr uint16_t sine_table_f32_period = 256;
// periode is 256 . means sine_table_f32[0]= sine_table_f32[0+256], sine_table_f32[1]=sine_table_f32[1+256] (those two added manualy)
// Then table has 257 values , [0,..255] + [256] and [257], those two are used when we interpolate[255] with [255+1], and [256] with [256+1]
// Then table has 258 values ,256:[0,..255] + [256] and [257], those two are used when we interpolate[255] with [255+1], and [256] with [256+1]
// [256] index is needed in the function sin_f32() when we are inputing very small radian values , example , sin_f32((-1e-14) in radians)
static constexpr std::array<float, sine_table_f32_period + 2> sine_table_f32{