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changed parity calculation from large table to a small function

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changed parity calculation to be on-the-fly during tag modulation
changed calls to parity function to use smaller function
This commit is contained in:
Peter Fillmore 2014-11-16 22:54:54 +11:00
commit 0c03a4f719
5 changed files with 34 additions and 9 deletions
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12
armsrc/iclass.c
View file

@ -226,7 +226,8 @@ static RAMFUNC int OutOfNDecoding(int bit)
// Calculate the parity bit for the client...
Uart.parityBits <<= 1;
Uart.parityBits ^= OddByteParity[(Uart.shiftReg & 0xff)];
//Uart.parityBits ^= OddByteParity[(Uart.shiftReg & 0xff)];
Uart.parityBits ^= oddparity(Uart.shiftReg & 0xff);
Uart.bitCnt = 0;
Uart.shiftReg = 0;
@ -249,7 +250,8 @@ static RAMFUNC int OutOfNDecoding(int bit)
// Calculate the parity bit for the client...
Uart.parityBits <<= 1;
Uart.parityBits ^= OddByteParity[(Uart.dropPosition & 0xff)];
//Uart.parityBits ^= OddByteParity[(Uart.dropPosition & 0xff)];
Uart.parityBits ^= oddparity((Uart.dropPosition & 0xff));
Uart.bitCnt = 0;
Uart.shiftReg = 0;
@ -486,7 +488,8 @@ static RAMFUNC int ManchesterDecoding(int v)
Demod.output[Demod.len] = 0x0f;
Demod.len++;
Demod.parityBits <<= 1;
Demod.parityBits ^= OddByteParity[0x0f];
//Demod.parityBits ^= OddByteParity[0x0f];
Demod.parityBits ^= oddparity(0x0f);
Demod.state = DEMOD_UNSYNCD;
// error = 0x0f;
return TRUE;
@ -611,7 +614,8 @@ static RAMFUNC int ManchesterDecoding(int v)
// FOR ISO15639 PARITY NOT SEND OTA, JUST CALCULATE IT FOR THE CLIENT
Demod.parityBits <<= 1;
Demod.parityBits ^= OddByteParity[(Demod.shiftReg & 0xff)];
//Demod.parityBits ^= OddByteParity[(Demod.shiftReg & 0xff)];
Demod.parityBits ^= oddparity(Demod.shiftReg & 0xff);
Demod.bitCount = 0;
Demod.shiftReg = 0;

18
armsrc/iso14443a.c
View file

@ -125,6 +125,8 @@ uint32_t LastProxToAirDuration;
#define SEC_Y 0x00
#define SEC_Z 0xc0
//replaced large parity table with small parity generation function - saves flash code
/*
const uint8_t OddByteParity[256] = {
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1,
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
@ -143,8 +145,7 @@ const uint8_t OddByteParity[256] = {
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,
1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1
};
*/
void iso14a_set_trigger(bool enable) {
trigger = enable;
}
@ -166,10 +167,14 @@ void iso14a_set_timeout(uint32_t timeout) {
// Generate the parity value for a byte sequence
//
//-----------------------------------------------------------------------------
/*
byte_t oddparity (const byte_t bt)
{
return OddByteParity[bt];
}
*/
uint32_t GetParity(const uint8_t * pbtCmd, int iLen)
{
@ -179,7 +184,8 @@ uint32_t GetParity(const uint8_t * pbtCmd, int iLen)
// Generate the parity bits
for (i = 0; i < iLen; i++) {
// and save them to a 32Bit word
dwPar |= ((OddByteParity[pbtCmd[i]]) << i);
//dwPar |= ((OddByteParity[pbtCmd[i]]) << i);
dwPar |= (oddparity(pbtCmd[i]) << i);
}
return dwPar;
}
@ -648,6 +654,7 @@ void RAMFUNC SnoopIso14443a(uint8_t param) {
//-----------------------------------------------------------------------------
// Prepare tag messages
//16/11/2014 - changed to calculate parity on the fly - Peter Fillmore
//-----------------------------------------------------------------------------
static void CodeIso14443aAsTagPar(const uint8_t *cmd, int len, uint32_t dwParity)
{
@ -684,13 +691,16 @@ static void CodeIso14443aAsTagPar(const uint8_t *cmd, int len, uint32_t dwParity
}
// Get the parity bit
if ((dwParity >> i) & 0x01) {
// changed to generate parity on the fly
//if ((dwParity >> i) & 0x01) {
if (oddparity(cmd[i]) & 0x01) {
ToSend[++ToSendMax] = SEC_D;
LastProxToAirDuration = 8 * ToSendMax - 4;
} else {
ToSend[++ToSendMax] = SEC_E;
LastProxToAirDuration = 8 * ToSendMax;
}
}
// Send stopbit

2
armsrc/iso14443a.h
View file

@ -75,7 +75,7 @@ typedef struct {
extern byte_t oddparity (const byte_t bt);
//extern uint8_t oddparity(uint8_t bt);
extern uint32_t GetParity(const uint8_t *pbtCmd, int iLen);
extern void AppendCrc14443a(uint8_t *data, int len);

8
armsrc/util.c
View file

@ -44,7 +44,15 @@ uint64_t bytes_to_num(uint8_t* src, size_t len)
}
return num;
}
//added here for parity calulations
uint8_t oddparity(uint8_t bt)
{
uint16_t v = bt;
v ^= v >> 4;
v &= 0xF;
return ((0x9669 >> v) & 1);
}
void LEDsoff()
{
LED_A_OFF();

3
armsrc/util.h
View file

@ -32,6 +32,9 @@ uint32_t SwapBits(uint32_t value, int nrbits);
void num_to_bytes(uint64_t n, size_t len, uint8_t* dest);
uint64_t bytes_to_num(uint8_t* src, size_t len);
//added parity generation function here
uint8_t oddparity(uint8_t bt);
void SpinDelay(int ms);
void SpinDelayUs(int us);
void LED(int led, int ms);