[proxmark3-svn] / armsrc / lfsampling.c

//-----------------------------------------------------------------------------
// This code is licensed to you under the terms of the GNU GPL, version 2 or,
// at your option, any later version. See the LICENSE.txt file for the text of
// the license.
//-----------------------------------------------------------------------------
// Miscellaneous routines for low frequency sampling.
//-----------------------------------------------------------------------------

#include "proxmark3.h"
#include "apps.h"
#include "util.h"
#include "string.h"
#include "usb_cdc.h" // for usb_poll_validate_length
#include "lfsampling.h"

sample_config config = { 1, 8, 1, 95, 0 } ;

void printConfig()
{
	Dbprintf("LF Sampling config: ");
	Dbprintf("  [q] divisor:           %d ", config.divisor);
	Dbprintf("  [b] bps:               %d ", config.bits_per_sample);
	Dbprintf("  [d] decimation:        %d ", config.decimation);
	Dbprintf("  [a] averaging:         %d ", config.averaging);
	Dbprintf("  [t] trigger threshold: %d ", config.trigger_threshold);
}


/**
 * Called from the USB-handler to set the sampling configuration
 * The sampling config is used for std reading and snooping.
 *
 * Other functions may read samples and ignore the sampling config,
 * such as functions to read the UID from a prox tag or similar.
 *
 * Values set to '0' implies no change (except for averaging)
 * @brief setSamplingConfig
 * @param sc
 */
void setSamplingConfig(sample_config *sc)
{
	if(sc->divisor != 0) config.divisor = sc->divisor;
	if(sc->bits_per_sample!= 0) config.bits_per_sample= sc->bits_per_sample;
	if(sc->decimation!= 0) config.decimation= sc->decimation;
	if(sc->trigger_threshold != -1) config.trigger_threshold= sc->trigger_threshold;

	config.averaging= sc->averaging;
	if(config.bits_per_sample > 8)	config.bits_per_sample = 8;
	if(config.decimation < 1)	config.decimation = 1;

	printConfig();
}

sample_config* getSamplingConfig()
{
	return &config;
}

typedef struct {
	uint8_t * buffer;
	uint32_t numbits;
	uint32_t position;
} BitstreamOut;

/**
 * @brief Pushes bit onto the stream
 * @param stream
 * @param bit
 */
void pushBit( BitstreamOut* stream, uint8_t bit)
{
	int bytepos = stream->position >> 3; // divide by 8
	int bitpos = stream->position & 7;
	*(stream->buffer+bytepos) |= (bit > 0) <<  (7 - bitpos);
	stream->position++;
	stream->numbits++;
}

/**
* Setup the FPGA to listen for samples. This method downloads the FPGA bitstream
* if not already loaded, sets divisor and starts up the antenna.
* @param divisor : 1, 88> 255 or negative ==> 134.8 KHz
* 				   0 or 95 ==> 125 KHz
*
**/
void LFSetupFPGAForADC(int divisor, bool lf_field)
{
	FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
	if ( (divisor == 1) || (divisor < 0) || (divisor > 255) )
		FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
	else if (divisor == 0)
		FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
	else
		FpgaSendCommand(FPGA_CMD_SET_DIVISOR, divisor);

	FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_ADC | (lf_field ? FPGA_LF_ADC_READER_FIELD : 0));

	// Connect the A/D to the peak-detected low-frequency path.
	SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
	// Give it a bit of time for the resonant antenna to settle.
	SpinDelay(50);
	// Now set up the SSC to get the ADC samples that are now streaming at us.
	FpgaSetupSsc();
}

/**
 * Does the sample acquisition. If threshold is specified, the actual sampling
 * is not commenced until the threshold has been reached.
 * This method implements decimation and quantization in order to
 * be able to provide longer sample traces.
 * Uses the following global settings:
 * @param decimation - how much should the signal be decimated. A decimation of N means we keep 1 in N samples, etc.
 * @param bits_per_sample - bits per sample. Max 8, min 1 bit per sample.
 * @param averaging If set to true, decimation will use averaging, so that if e.g. decimation is 3, the sample
 * value that will be used is the average value of the three samples.
 * @param trigger_threshold - a threshold. The sampling won't commence until this threshold has been reached. Set
 * to -1 to ignore threshold.
 * @param silent - is true, now outputs are made. If false, dbprints the status
 * @return the number of bits occupied by the samples.
 */
uint32_t DoAcquisition(uint8_t decimation, uint32_t bits_per_sample, bool averaging, int trigger_threshold, bool silent)
{
	//.
	uint8_t *dest = BigBuf_get_addr();
    int bufsize = BigBuf_max_traceLen();

	//memset(dest, 0, bufsize); //creates issues with cmdread (marshmellow)

	if(bits_per_sample < 1) bits_per_sample = 1;
	if(bits_per_sample > 8) bits_per_sample = 8;

	if(decimation < 1) decimation = 1;

	// Use a bit stream to handle the output
	BitstreamOut data = { dest , 0, 0};
	int sample_counter = 0;
	uint8_t sample = 0;
	//If we want to do averaging
	uint32_t sample_sum =0 ;
	uint32_t sample_total_numbers =0 ;
	uint32_t sample_total_saved =0 ;

	while(!BUTTON_PRESS()) {
		WDT_HIT();
		if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
			AT91C_BASE_SSC->SSC_THR = 0x43;
			LED_D_ON();
		}
		if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
			sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
			LED_D_OFF();
			// threshold either high or low values 128 = center 0.  if trigger = 178 
			if ((trigger_threshold > 0) && (sample < (trigger_threshold+128)) && (sample > (128-trigger_threshold))) // 
				continue;
		
			trigger_threshold = 0;
			sample_total_numbers++;

			if(averaging)
			{
				sample_sum += sample;
			}
			//Check decimation
			if(decimation > 1)
			{
				sample_counter++;
				if(sample_counter < decimation) continue;
				sample_counter = 0;
			}
			//Averaging
			if(averaging && decimation > 1) {
				sample = sample_sum / decimation;
				sample_sum =0;
			}
			//Store the sample
			sample_total_saved ++;
			if(bits_per_sample == 8){
				dest[sample_total_saved-1] = sample;
				data.numbits = sample_total_saved << 3;//Get the return value correct
				if(sample_total_saved >= bufsize) break;
			}
			else{
				pushBit(&data, sample & 0x80);
				if(bits_per_sample > 1)	pushBit(&data, sample & 0x40);
				if(bits_per_sample > 2)	pushBit(&data, sample & 0x20);
				if(bits_per_sample > 3)	pushBit(&data, sample & 0x10);
				if(bits_per_sample > 4)	pushBit(&data, sample & 0x08);
				if(bits_per_sample > 5)	pushBit(&data, sample & 0x04);
				if(bits_per_sample > 6)	pushBit(&data, sample & 0x02);
				//Not needed, 8bps is covered above
				//if(bits_per_sample > 7)	pushBit(&data, sample & 0x01);
				if((data.numbits >> 3) +1  >= bufsize) break;
			}
		}
	}

	if(!silent)
	{
		Dbprintf("Done, saved %d out of %d seen samples at %d bits/sample",sample_total_saved, sample_total_numbers,bits_per_sample);
		Dbprintf("buffer samples: %02x %02x %02x %02x %02x %02x %02x %02x ...",
					dest[0], dest[1], dest[2], dest[3], dest[4], dest[5], dest[6], dest[7]);
	}
	return data.numbits;
}
/**
 * @brief Does sample acquisition, ignoring the config values set in the sample_config.
 * This method is typically used by tag-specific readers who just wants to read the samples
 * the normal way
 * @param trigger_threshold
 * @param silent
 * @return number of bits sampled
 */
uint32_t DoAcquisition_default(int trigger_threshold, bool silent)
{
	return DoAcquisition(1,8,0,trigger_threshold,silent);
}
uint32_t DoAcquisition_config( bool silent)
{
	return DoAcquisition(config.decimation
				  ,config.bits_per_sample
				  ,config.averaging
				  ,config.trigger_threshold
				  ,silent);
}

uint32_t ReadLF(bool activeField, bool silent)
{
	if (!silent) printConfig();
	LFSetupFPGAForADC(config.divisor, activeField);
	// Now call the acquisition routine
	return DoAcquisition_config(silent);
}

/**
* Initializes the FPGA for reader-mode (field on), and acquires the samples.
* @return number of bits sampled
**/
uint32_t SampleLF(bool printCfg)
{
	return ReadLF(true, printCfg);
}
/**
* Initializes the FPGA for snoop-mode (field off), and acquires the samples.
* @return number of bits sampled
**/

uint32_t SnoopLF()
{
	return ReadLF(false, true);
}

/**
* acquisition of T55x7 LF signal. Similart to other LF, but adjusted with @marshmellows thresholds
* the data is collected in BigBuf.
**/
void doT55x7Acquisition(size_t sample_size) {

	#define T55xx_READ_UPPER_THRESHOLD 128+60  // 60 grph
	#define T55xx_READ_LOWER_THRESHOLD 128-60  // -60 grph
	#define T55xx_READ_TOL   5

	uint8_t *dest = BigBuf_get_addr();
	uint16_t bufsize = BigBuf_max_traceLen();
	
	if ( bufsize > sample_size )
		bufsize = sample_size;

	uint16_t i = 0;
	bool startFound = false;
	bool highFound = false;
	bool lowFound = false;
	uint8_t curSample = 0;
	uint8_t lastSample = 0;
	uint16_t skipCnt = 0;
	while(!BUTTON_PRESS() && !usb_poll_validate_length() && skipCnt<1000 && i<bufsize ) {
		WDT_HIT();
		if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
			AT91C_BASE_SSC->SSC_THR = 0x43;
			LED_D_ON();
		}
		if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
			curSample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
			LED_D_OFF();

			// skip until the first high sample above threshold
			if (!startFound && curSample > T55xx_READ_UPPER_THRESHOLD) {
				//if (curSample > lastSample) 
				//	lastSample = curSample;
				highFound = true;
			} else if (!highFound) {
				skipCnt++;
				continue;
			}
			// skip until the first Low sample below threshold
			if (!startFound && curSample < T55xx_READ_LOWER_THRESHOLD) {
				//if (curSample > lastSample) 
				lastSample = curSample;
				lowFound = true;
			} else if (!lowFound) {
				skipCnt++;
				continue;
			}


			// skip until first high samples begin to change
			if (startFound || curSample > T55xx_READ_LOWER_THRESHOLD+T55xx_READ_TOL){
				// if just found start - recover last sample
				if (!startFound) {
					dest[i++] = lastSample;
					startFound = true;
				}
				// collect samples
				dest[i++] = curSample;
			}
		}
	}
}
Commit	Line	Data
31abe49f MHS	1	//-----------------------------------------------------------------------------
	2	// This code is licensed to you under the terms of the GNU GPL, version 2 or,
	3	// at your option, any later version. See the LICENSE.txt file for the text of
	4	// the license.
	5	//-----------------------------------------------------------------------------
	6	// Miscellaneous routines for low frequency sampling.
	7	//-----------------------------------------------------------------------------
	8
	9	#include "proxmark3.h"
	10	#include "apps.h"
	11	#include "util.h"
	12	#include "string.h"
506672c4	13	#include "usb_cdc.h" // for usb_poll_validate_length
31abe49f	14	#include "lfsampling.h"
10a8875c	15
0cd2a41a	16	sample_config config = { 1, 8, 1, 95, 0 } ;
31abe49f MHS	17
	18	void printConfig()
	19	{
e2012d1b	20	Dbprintf("LF Sampling config: ");
31abe49f MHS	21	Dbprintf(" [q] divisor: %d ", config.divisor);
	22	Dbprintf(" [b] bps: %d ", config.bits_per_sample);
	23	Dbprintf(" [d] decimation: %d ", config.decimation);
	24	Dbprintf(" [a] averaging: %d ", config.averaging);
	25	Dbprintf(" [t] trigger threshold: %d ", config.trigger_threshold);
	26	}
	27
	28
	29	/**
	30	* Called from the USB-handler to set the sampling configuration
	31	* The sampling config is used for std reading and snooping.
	32	*
	33	* Other functions may read samples and ignore the sampling config,
	34	* such as functions to read the UID from a prox tag or similar.
	35	*
	36	* Values set to '0' implies no change (except for averaging)
	37	* @brief setSamplingConfig
	38	* @param sc
	39	*/
	40	void setSamplingConfig(sample_config *sc)
	41	{
	42	if(sc->divisor != 0) config.divisor = sc->divisor;
	43	if(sc->bits_per_sample!= 0) config.bits_per_sample= sc->bits_per_sample;
	44	if(sc->decimation!= 0) config.decimation= sc->decimation;
	45	if(sc->trigger_threshold != -1) config.trigger_threshold= sc->trigger_threshold;
	46
	47	config.averaging= sc->averaging;
	48	if(config.bits_per_sample > 8) config.bits_per_sample = 8;
	49	if(config.decimation < 1) config.decimation = 1;
	50
	51	printConfig();
	52	}
	53
	54	sample_config* getSamplingConfig()
	55	{
	56	return &config;
	57	}
10a8875c	58
31abe49f MHS	59	typedef struct {
	60	uint8_t * buffer;
	61	uint32_t numbits;
	62	uint32_t position;
	63	} BitstreamOut;
	64
31abe49f MHS	65	/**
	66	* @brief Pushes bit onto the stream
	67	* @param stream
	68	* @param bit
	69	*/
10a8875c	70	void pushBit( BitstreamOut* stream, uint8_t bit)
31abe49f MHS	71	{
	72	int bytepos = stream->position >> 3; // divide by 8
	73	int bitpos = stream->position & 7;
	74	*(stream->buffer+bytepos) \|= (bit > 0) << (7 - bitpos);
	75	stream->position++;
	76	stream->numbits++;
	77	}
10a8875c	78
31abe49f MHS	79	/**
	80	* Setup the FPGA to listen for samples. This method downloads the FPGA bitstream
	81	* if not already loaded, sets divisor and starts up the antenna.
	82	* @param divisor : 1, 88> 255 or negative ==> 134.8 KHz
	83	* 0 or 95 ==> 125 KHz
	84	*
	85	**/
	86	void LFSetupFPGAForADC(int divisor, bool lf_field)
	87	{
	88	FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
	89	if ( (divisor == 1) \|\| (divisor < 0) \|\| (divisor > 255) )
	90	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
	91	else if (divisor == 0)
	92	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
	93	else
	94	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, divisor);
	95
	96	FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_ADC \| (lf_field ? FPGA_LF_ADC_READER_FIELD : 0));
	97
	98	// Connect the A/D to the peak-detected low-frequency path.
	99	SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
	100	// Give it a bit of time for the resonant antenna to settle.
	101	SpinDelay(50);
	102	// Now set up the SSC to get the ADC samples that are now streaming at us.
	103	FpgaSetupSsc();
	104	}
	105
31abe49f MHS	106	/**
	107	* Does the sample acquisition. If threshold is specified, the actual sampling
	108	* is not commenced until the threshold has been reached.
	109	* This method implements decimation and quantization in order to
	110	* be able to provide longer sample traces.
	111	* Uses the following global settings:
	112	* @param decimation - how much should the signal be decimated. A decimation of N means we keep 1 in N samples, etc.
	113	* @param bits_per_sample - bits per sample. Max 8, min 1 bit per sample.
	114	* @param averaging If set to true, decimation will use averaging, so that if e.g. decimation is 3, the sample
	115	* value that will be used is the average value of the three samples.
	116	* @param trigger_threshold - a threshold. The sampling won't commence until this threshold has been reached. Set
	117	* to -1 to ignore threshold.
	118	* @param silent - is true, now outputs are made. If false, dbprints the status
	119	* @return the number of bits occupied by the samples.
	120	*/
b29d55f2	121	uint32_t DoAcquisition(uint8_t decimation, uint32_t bits_per_sample, bool averaging, int trigger_threshold, bool silent)
31abe49f MHS	122	{
31abe49f MHS	123	//.
0644d5e3 MHS	124	uint8_t *dest = BigBuf_get_addr();
	125	int bufsize = BigBuf_max_traceLen();
	126
3cec7061	127	//memset(dest, 0, bufsize); //creates issues with cmdread (marshmellow)
31abe49f MHS	128
	129	if(bits_per_sample < 1) bits_per_sample = 1;
	130	if(bits_per_sample > 8) bits_per_sample = 8;
	131
	132	if(decimation < 1) decimation = 1;
	133
	134	// Use a bit stream to handle the output
	135	BitstreamOut data = { dest , 0, 0};
	136	int sample_counter = 0;
	137	uint8_t sample = 0;
	138	//If we want to do averaging
	139	uint32_t sample_sum =0 ;
	140	uint32_t sample_total_numbers =0 ;
	141	uint32_t sample_total_saved =0 ;
	142
	143	while(!BUTTON_PRESS()) {
	144	WDT_HIT();
	145	if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
	146	AT91C_BASE_SSC->SSC_THR = 0x43;
	147	LED_D_ON();
	148	}
	149	if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
	150	sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
	151	LED_D_OFF();
b29d55f2	152	// threshold either high or low values 128 = center 0. if trigger = 178
b29d55f2	153	if ((trigger_threshold > 0) && (sample < (trigger_threshold+128)) && (sample > (128-trigger_threshold))) //
31abe49f	154	continue;
b29d55f2	155
31abe49f MHS	156	trigger_threshold = 0;
	157	sample_total_numbers++;
	158
	159	if(averaging)
	160	{
	161	sample_sum += sample;
	162	}
	163	//Check decimation
	164	if(decimation > 1)
	165	{
	166	sample_counter++;
	167	if(sample_counter < decimation) continue;
	168	sample_counter = 0;
	169	}
	170	//Averaging
	171	if(averaging && decimation > 1) {
	172	sample = sample_sum / decimation;
	173	sample_sum =0;
	174	}
	175	//Store the sample
	176	sample_total_saved ++;
	177	if(bits_per_sample == 8){
	178	dest[sample_total_saved-1] = sample;
	179	data.numbits = sample_total_saved << 3;//Get the return value correct
	180	if(sample_total_saved >= bufsize) break;
	181	}
	182	else{
	183	pushBit(&data, sample & 0x80);
	184	if(bits_per_sample > 1) pushBit(&data, sample & 0x40);
	185	if(bits_per_sample > 2) pushBit(&data, sample & 0x20);
	186	if(bits_per_sample > 3) pushBit(&data, sample & 0x10);
	187	if(bits_per_sample > 4) pushBit(&data, sample & 0x08);
	188	if(bits_per_sample > 5) pushBit(&data, sample & 0x04);
	189	if(bits_per_sample > 6) pushBit(&data, sample & 0x02);
	190	//Not needed, 8bps is covered above
	191	//if(bits_per_sample > 7) pushBit(&data, sample & 0x01);
	192	if((data.numbits >> 3) +1 >= bufsize) break;
	193	}
	194	}
	195	}
	196
	197	if(!silent)
	198	{
	199	Dbprintf("Done, saved %d out of %d seen samples at %d bits/sample",sample_total_saved, sample_total_numbers,bits_per_sample);
	200	Dbprintf("buffer samples: %02x %02x %02x %02x %02x %02x %02x %02x ...",
	201	dest[0], dest[1], dest[2], dest[3], dest[4], dest[5], dest[6], dest[7]);
	202	}
	203	return data.numbits;
	204	}
	205	/**
	206	* @brief Does sample acquisition, ignoring the config values set in the sample_config.
	207	* This method is typically used by tag-specific readers who just wants to read the samples
	208	* the normal way
	209	* @param trigger_threshold
	210	* @param silent
	211	* @return number of bits sampled
	212	*/
	213	uint32_t DoAcquisition_default(int trigger_threshold, bool silent)
	214	{
	215	return DoAcquisition(1,8,0,trigger_threshold,silent);
	216	}
	217	uint32_t DoAcquisition_config( bool silent)
	218	{
	219	return DoAcquisition(config.decimation
220	,config.bits_per_sample
221	,config.averaging
222	,config.trigger_threshold
223	,silent);
224	}
225
1fbf8956	226	uint32_t ReadLF(bool activeField, bool silent)
31abe49f	227	{
1fbf8956	228	if (!silent) printConfig();
31abe49f MHS	229	LFSetupFPGAForADC(config.divisor, activeField);
31abe49f MHS	230	// Now call the acquisition routine
1fbf8956	231	return DoAcquisition_config(silent);
31abe49f MHS	232	}
	233
	234	/**
	235	* Initializes the FPGA for reader-mode (field on), and acquires the samples.
	236	* @return number of bits sampled
	237	**/
1fbf8956	238	uint32_t SampleLF(bool printCfg)
31abe49f	239	{
1fbf8956	240	return ReadLF(true, printCfg);
31abe49f MHS	241	}
	242	/**
	243	* Initializes the FPGA for snoop-mode (field off), and acquires the samples.
	244	* @return number of bits sampled
	245	**/
	246
	247	uint32_t SnoopLF()
	248	{
1fbf8956	249	return ReadLF(false, true);
31abe49f	250	}
7cfc777b	251
	252	/**
	253	* acquisition of T55x7 LF signal. Similart to other LF, but adjusted with @marshmellows thresholds
	254	* the data is collected in BigBuf.
	255	**/
66837a03	256	void doT55x7Acquisition(size_t sample_size) {
7cfc777b	257
6fe5c94b	258	#define T55xx_READ_UPPER_THRESHOLD 128+60 // 60 grph
6fe5c94b	259	#define T55xx_READ_LOWER_THRESHOLD 128-60 // -60 grph
7cfc777b	260	#define T55xx_READ_TOL 5
	261
	262	uint8_t *dest = BigBuf_get_addr();
	263	uint16_t bufsize = BigBuf_max_traceLen();
	264
66837a03	265	if ( bufsize > sample_size )
66837a03	266	bufsize = sample_size;
7cfc777b	267
7cfc777b	268	uint16_t i = 0;
	269	bool startFound = false;
	270	bool highFound = false;
6fe5c94b	271	bool lowFound = false;
7cfc777b	272	uint8_t curSample = 0;
db829602	273	uint8_t lastSample = 0;
be2d41b7	274	uint16_t skipCnt = 0;
506672c4	275	while(!BUTTON_PRESS() && !usb_poll_validate_length() && skipCnt<1000 && i<bufsize ) {
be2d41b7	276	WDT_HIT();
7cfc777b	277	if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
	278	AT91C_BASE_SSC->SSC_THR = 0x43;
	279	LED_D_ON();
	280	}
	281	if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
	282	curSample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
be2d41b7	283	LED_D_OFF();
be2d41b7	284
9f669cb2	285	// skip until the first high sample above threshold
7cfc777b	286	if (!startFound && curSample > T55xx_READ_UPPER_THRESHOLD) {
6fe5c94b	287	//if (curSample > lastSample)
6fe5c94b	288	// lastSample = curSample;
7cfc777b	289	highFound = true;
7cfc777b	290	} else if (!highFound) {
be2d41b7	291	skipCnt++;
7cfc777b	292	continue;
7cfc777b	293	}
6fe5c94b	294	// skip until the first Low sample below threshold
	295	if (!startFound && curSample < T55xx_READ_LOWER_THRESHOLD) {
	296	//if (curSample > lastSample)
	297	lastSample = curSample;
	298	lowFound = true;
	299	} else if (!lowFound) {
	300	skipCnt++;
	301	continue;
	302	}
	303
	304
9f669cb2	305	// skip until first high samples begin to change
6fe5c94b	306	if (startFound \|\| curSample > T55xx_READ_LOWER_THRESHOLD+T55xx_READ_TOL){
9f669cb2	307	// if just found start - recover last sample
9f669cb2	308	if (!startFound) {
db829602	309	dest[i++] = lastSample;
9f669cb2	310	startFound = true;
	311	}
	312	// collect samples
7cfc777b	313	dest[i++] = curSample;
7cfc777b	314	}
	315	}
	316	}
	317	}