Table-ize the Mode A to C conversions, add a Mode C to Mode A conversion function.

This commit is contained in:
Oliver Jowett 2016-10-11 17:57:25 +01:00
parent 10b5cde505
commit 60f1f3bcb6
7 changed files with 68 additions and 7 deletions

View file

@ -243,6 +243,7 @@ void modesInit(void) {
// Prepare error correction tables // Prepare error correction tables
modesChecksumInit(Modes.nfix_crc); modesChecksumInit(Modes.nfix_crc);
icaoFilterInit(); icaoFilterInit();
modeACInit();
if (Modes.show_only) if (Modes.show_only)
icaoFilterAdd(Modes.show_only); icaoFilterAdd(Modes.show_only);

View file

@ -550,7 +550,9 @@ extern "C" {
// //
int detectModeA (uint16_t *m, struct modesMessage *mm); int detectModeA (uint16_t *m, struct modesMessage *mm);
void decodeModeAMessage(struct modesMessage *mm, int ModeA); void decodeModeAMessage(struct modesMessage *mm, int ModeA);
int ModeAToModeC (unsigned int ModeA); void modeACInit();
int modeAToModeC (unsigned int modeA);
unsigned modeCToModeA (int modeC);
// //
// Functions exported from mode_s.c // Functions exported from mode_s.c

View file

@ -95,6 +95,7 @@ static void faupInit(void) {
// Prepare error correction tables // Prepare error correction tables
modesChecksumInit(1); modesChecksumInit(1);
icaoFilterInit(); icaoFilterInit();
modeACInit();
} }
// //

View file

@ -29,15 +29,59 @@
// //
#include "dump1090.h" #include "dump1090.h"
#include <assert.h>
// //
//========================================================================= //=========================================================================
// //
// Input format is : 00:A4:A2:A1:00:B4:B2:B1:00:C4:C2:C1:00:D4:D2:D1 // Input format is : 00:A4:A2:A1:00:B4:B2:B1:00:C4:C2:C1:00:D4:D2:D1
// //
int ModeAToModeC(unsigned int ModeA)
static int modeAToCTable[4096];
static unsigned modeCToATable[4096];
static int internalModeAToModeC(unsigned int ModeA);
void modeACInit()
{ {
unsigned int FiveHundreds = 0; for (unsigned i = 0; i < 4096; ++i) {
unsigned int OneHundreds = 0; unsigned modeA = indexToModeA(i);
int modeC = internalModeAToModeC(modeA);
modeAToCTable[i] = modeC;
modeC += 13;
if (modeC >= 0 && modeC < 4096) {
assert(modeCToATable[modeC] == 0);
modeCToATable[modeC] = modeA;
}
}
}
// Given a mode A value (hex-encoded, see above)
// return the mode C value (signed multiple of 100s of feet)
// or INVALID_ALITITUDE if not a valid mode C value
int modeAToModeC(unsigned modeA)
{
unsigned i = modeAToIndex(modeA);
if (i >= 4096)
return INVALID_ALTITUDE;
return modeAToCTable[i];
}
// Given a mode C value (signed multiple of 100s of feet)
// return the mode A value, or 0 if not a valid mode C value
unsigned modeCToModeA(int modeC)
{
modeC += 13;
if (modeC < 0 || modeC >= 4096)
return 0;
return modeCToATable[modeC];
}
static int internalModeAToModeC(unsigned int ModeA)
{
unsigned int FiveHundreds = 0;
unsigned int OneHundreds = 0;
if ((ModeA & 0xFFFF8889) != 0 || // check zero bits are zero, D1 set is illegal if ((ModeA & 0xFFFF8889) != 0 || // check zero bits are zero, D1 set is illegal
(ModeA & 0x000000F0) == 0) { // C1,,C4 cannot be Zero (ModeA & 0x000000F0) == 0) { // C1,,C4 cannot be Zero
@ -100,7 +144,7 @@ void decodeModeAMessage(struct modesMessage *mm, int ModeA)
// Decode an altitude if this looks like a possible mode C // Decode an altitude if this looks like a possible mode C
if (!mm->spi) { if (!mm->spi) {
int modeC = ModeAToModeC(ModeA); int modeC = modeAToModeC(ModeA);
if (modeC != INVALID_ALTITUDE) { if (modeC != INVALID_ALTITUDE) {
mm->altitude = modeC * 100; mm->altitude = modeC * 100;
mm->altitude_unit = UNIT_FEET; mm->altitude_unit = UNIT_FEET;

View file

@ -134,7 +134,7 @@ static int decodeAC13Field(int AC13Field, altitude_unit_t *unit) {
return ((n * 25) - 1000); return ((n * 25) - 1000);
} else { } else {
// N is an 11 bit Gillham coded altitude // N is an 11 bit Gillham coded altitude
int n = ModeAToModeC(decodeID13Field(AC13Field)); int n = modeAToModeC(decodeID13Field(AC13Field));
if (n < -12) { if (n < -12) {
return INVALID_ALTITUDE; return INVALID_ALTITUDE;
} }
@ -167,7 +167,7 @@ static int decodeAC12Field(int AC12Field, altitude_unit_t *unit) {
// Make N a 13 bit Gillham coded altitude by inserting M=0 at bit 6 // Make N a 13 bit Gillham coded altitude by inserting M=0 at bit 6
int n = ((AC12Field & 0x0FC0) << 1) | int n = ((AC12Field & 0x0FC0) << 1) |
(AC12Field & 0x003F); (AC12Field & 0x003F);
n = ModeAToModeC(decodeID13Field(n)); n = modeAToModeC(decodeID13Field(n));
if (n < -12) { if (n < -12) {
return INVALID_ALTITUDE; return INVALID_ALTITUDE;
} }

12
track.h
View file

@ -200,4 +200,16 @@ struct aircraft *trackUpdateFromMessage(struct modesMessage *mm);
/* Call periodically */ /* Call periodically */
void trackPeriodicUpdate(); void trackPeriodicUpdate();
/* Convert from a (hex) mode A value to a 0-4095 index */
static inline unsigned modeAToIndex(unsigned modeA)
{
return (modeA & 0x0007) | ((modeA & 0x0070) >> 1) | ((modeA & 0x0700) >> 2) | ((modeA & 0x7000) >> 3);
}
/* Convert from a 0-4095 index to a (hex) mode A value */
static inline unsigned indexToModeA(unsigned index)
{
return (index & 0007) | ((index & 0070) << 1) | ((index & 0700) << 2) | ((index & 07000) << 3);
}
#endif #endif

View file

@ -112,6 +112,7 @@ void view1090Init(void) {
// Prepare error correction tables // Prepare error correction tables
modesChecksumInit(Modes.nfix_crc); modesChecksumInit(Modes.nfix_crc);
icaoFilterInit(); icaoFilterInit();
modeACInit();
} }
// //