[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 "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;
}

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

/**
 * @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);
	// 50ms 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();
	// start a 1.5ticks is 1us
	StartTicks();
}

/**
 * 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) {
	//bigbuf, to hold the aquired raw data signal
	uint8_t *dest = BigBuf_get_addr();
    uint16_t bufsize = BigBuf_max_traceLen();

	//BigBuf_Clear_ext(false);	  //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() && !usb_poll_validate_length() ) {
		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);
	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+40  // 60 grph
	#define T55xx_READ_LOWER_THRESHOLD 128-40  // -60 grph
	#define T55xx_READ_TOL   2
	
	uint8_t *dest = BigBuf_get_addr();
	uint16_t bufsize = BigBuf_max_traceLen();
	
	if ( bufsize > sample_size )
		bufsize = sample_size;

	uint8_t curSample = 0, lastSample = 0;
	uint16_t i = 0, skipCnt = 0;
	bool startFound = false;
	bool highFound = false;
	bool lowFound = false;
		
	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; //43
			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
31abe49f	9	#include "lfsampling.h"
10a8875c	10
0cd2a41a	11	sample_config config = { 1, 8, 1, 95, 0 } ;
31abe49f	12
24c49d36	13	void printConfig() {
7838f4be	14	Dbprintf("LF Sampling config: ");
31abe49f MHS	15	Dbprintf(" [q] divisor: %d ", config.divisor);
	16	Dbprintf(" [b] bps: %d ", config.bits_per_sample);
	17	Dbprintf(" [d] decimation: %d ", config.decimation);
	18	Dbprintf(" [a] averaging: %d ", config.averaging);
	19	Dbprintf(" [t] trigger threshold: %d ", config.trigger_threshold);
	20	}
	21
	22
	23	/**
	24	* Called from the USB-handler to set the sampling configuration
	25	* The sampling config is used for std reading and snooping.
	26	*
	27	* Other functions may read samples and ignore the sampling config,
	28	* such as functions to read the UID from a prox tag or similar.
	29	*
	30	* Values set to '0' implies no change (except for averaging)
	31	* @brief setSamplingConfig
	32	* @param sc
	33	*/
24c49d36	34	void setSamplingConfig(sample_config *sc) {
31abe49f	35	if(sc->divisor != 0) config.divisor = sc->divisor;
9974991e	36	if(sc->bits_per_sample != 0) config.bits_per_sample = sc->bits_per_sample;
	37	if(sc->decimation != 0) config.decimation = sc->decimation;
	38	if(sc->trigger_threshold != -1) config.trigger_threshold = sc->trigger_threshold;
31abe49f	39
9974991e	40	config.averaging = sc->averaging;
31abe49f MHS	41	if(config.bits_per_sample > 8) config.bits_per_sample = 8;
	42	if(config.decimation < 1) config.decimation = 1;
	43
	44	printConfig();
	45	}
	46
24c49d36	47	sample_config* getSamplingConfig() {
31abe49f MHS	48	return &config;
31abe49f MHS	49	}
10a8875c	50
53d5dc64	51	struct BitstreamOut {
31abe49f MHS	52	uint8_t * buffer;
	53	uint32_t numbits;
	54	uint32_t position;
53d5dc64	55	};
31abe49f	56
31abe49f MHS	57	/**
	58	* @brief Pushes bit onto the stream
	59	* @param stream
	60	* @param bit
	61	*/
24c49d36	62	void pushBit( BitstreamOut* stream, uint8_t bit) {
31abe49f MHS	63	int bytepos = stream->position >> 3; // divide by 8
	64	int bitpos = stream->position & 7;
	65	*(stream->buffer+bytepos) \|= (bit > 0) << (7 - bitpos);
	66	stream->position++;
	67	stream->numbits++;
	68	}
10a8875c	69
31abe49f MHS	70	/**
	71	* Setup the FPGA to listen for samples. This method downloads the FPGA bitstream
	72	* if not already loaded, sets divisor and starts up the antenna.
	73	* @param divisor : 1, 88> 255 or negative ==> 134.8 KHz
	74	* 0 or 95 ==> 125 KHz
	75	*
	76	**/
24c49d36	77	void LFSetupFPGAForADC(int divisor, bool lf_field) {
31abe49f MHS	78	FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
	79	if ( (divisor == 1) \|\| (divisor < 0) \|\| (divisor > 255) )
	80	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 88); //134.8Khz
	81	else if (divisor == 0)
	82	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, 95); //125Khz
	83	else
	84	FpgaSendCommand(FPGA_CMD_SET_DIVISOR, divisor);
	85
	86	FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_ADC \| (lf_field ? FPGA_LF_ADC_READER_FIELD : 0));
	87
	88	// Connect the A/D to the peak-detected low-frequency path.
	89	SetAdcMuxFor(GPIO_MUXSEL_LOPKD);
8255e1a6	90	// 50ms for the resonant antenna to settle.
31abe49f MHS	91	SpinDelay(50);
	92	// Now set up the SSC to get the ADC samples that are now streaming at us.
	93	FpgaSetupSsc();
24c49d36	94	// start a 1.5ticks is 1us
24c49d36	95	StartTicks();
31abe49f MHS	96	}
31abe49f MHS	97
31abe49f MHS	98	/**
	99	* Does the sample acquisition. If threshold is specified, the actual sampling
	100	* is not commenced until the threshold has been reached.
	101	* This method implements decimation and quantization in order to
	102	* be able to provide longer sample traces.
	103	* Uses the following global settings:
	104	* @param decimation - how much should the signal be decimated. A decimation of N means we keep 1 in N samples, etc.
	105	* @param bits_per_sample - bits per sample. Max 8, min 1 bit per sample.
	106	* @param averaging If set to true, decimation will use averaging, so that if e.g. decimation is 3, the sample
	107	* value that will be used is the average value of the three samples.
	108	* @param trigger_threshold - a threshold. The sampling won't commence until this threshold has been reached. Set
	109	* to -1 to ignore threshold.
	110	* @param silent - is true, now outputs are made. If false, dbprints the status
	111	* @return the number of bits occupied by the samples.
	112	*/
24c49d36	113	uint32_t DoAcquisition(uint8_t decimation, uint32_t bits_per_sample, bool averaging, int trigger_threshold,bool silent) {
1c8fbeb9	114	//bigbuf, to hold the aquired raw data signal
0644d5e3	115	uint8_t *dest = BigBuf_get_addr();
1c8fbeb9	116	uint16_t bufsize = BigBuf_max_traceLen();
0644d5e3	117
c0f15a05	118	//BigBuf_Clear_ext(false); //creates issues with cmdread (marshmellow)
31abe49f MHS	119
	120	if(bits_per_sample < 1) bits_per_sample = 1;
	121	if(bits_per_sample > 8) bits_per_sample = 8;
	122
	123	if(decimation < 1) decimation = 1;
	124
	125	// Use a bit stream to handle the output
	126	BitstreamOut data = { dest , 0, 0};
	127	int sample_counter = 0;
	128	uint8_t sample = 0;
	129	//If we want to do averaging
	130	uint32_t sample_sum =0 ;
	131	uint32_t sample_total_numbers =0 ;
	132	uint32_t sample_total_saved =0 ;
	133
edaf10af	134	while(!BUTTON_PRESS() && !usb_poll_validate_length() ) {
31abe49f MHS	135	WDT_HIT();
	136	if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
	137	AT91C_BASE_SSC->SSC_THR = 0x43;
	138	LED_D_ON();
	139	}
	140	if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
	141	sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
	142	LED_D_OFF();
99cf19d9	143	// threshold either high or low values 128 = center 0. if trigger = 178
99cf19d9	144	if ((trigger_threshold > 0) && (sample < (trigger_threshold+128)) && (sample > (128-trigger_threshold))) //
31abe49f MHS	145	continue;
	146
	147	trigger_threshold = 0;
	148	sample_total_numbers++;
	149
	150	if(averaging)
	151	{
	152	sample_sum += sample;
	153	}
	154	//Check decimation
	155	if(decimation > 1)
	156	{
	157	sample_counter++;
	158	if(sample_counter < decimation) continue;
	159	sample_counter = 0;
	160	}
	161	//Averaging
	162	if(averaging && decimation > 1) {
	163	sample = sample_sum / decimation;
	164	sample_sum =0;
	165	}
	166	//Store the sample
	167	sample_total_saved ++;
	168	if(bits_per_sample == 8){
	169	dest[sample_total_saved-1] = sample;
	170	data.numbits = sample_total_saved << 3;//Get the return value correct
	171	if(sample_total_saved >= bufsize) break;
	172	}
	173	else{
	174	pushBit(&data, sample & 0x80);
	175	if(bits_per_sample > 1) pushBit(&data, sample & 0x40);
	176	if(bits_per_sample > 2) pushBit(&data, sample & 0x20);
	177	if(bits_per_sample > 3) pushBit(&data, sample & 0x10);
	178	if(bits_per_sample > 4) pushBit(&data, sample & 0x08);
	179	if(bits_per_sample > 5) pushBit(&data, sample & 0x04);
	180	if(bits_per_sample > 6) pushBit(&data, sample & 0x02);
	181	//Not needed, 8bps is covered above
	182	//if(bits_per_sample > 7) pushBit(&data, sample & 0x01);
	183	if((data.numbits >> 3) +1 >= bufsize) break;
	184	}
	185	}
	186	}
	187
	188	if(!silent)
	189	{
	190	Dbprintf("Done, saved %d out of %d seen samples at %d bits/sample",sample_total_saved, sample_total_numbers,bits_per_sample);
	191	Dbprintf("buffer samples: %02x %02x %02x %02x %02x %02x %02x %02x ...",
	192	dest[0], dest[1], dest[2], dest[3], dest[4], dest[5], dest[6], dest[7]);
	193	}
	194	return data.numbits;
	195	}
	196	/**
	197	* @brief Does sample acquisition, ignoring the config values set in the sample_config.
	198	* This method is typically used by tag-specific readers who just wants to read the samples
	199	* the normal way
	200	* @param trigger_threshold
	201	* @param silent
	202	* @return number of bits sampled
	203	*/
24c49d36	204	uint32_t DoAcquisition_default(int trigger_threshold, bool silent) {
31abe49f MHS	205	return DoAcquisition(1,8,0,trigger_threshold,silent);
31abe49f MHS	206	}
24c49d36	207	uint32_t DoAcquisition_config( bool silent) {
31abe49f MHS	208	return DoAcquisition(config.decimation
	209	,config.bits_per_sample
	210	,config.averaging
	211	,config.trigger_threshold
	212	,silent);
	213	}
	214
24c49d36	215	uint32_t ReadLF(bool activeField, bool silent) {
	216	if (!silent)
	217	printConfig();
31abe49f	218	LFSetupFPGAForADC(config.divisor, activeField);
1fbf8956	219	return DoAcquisition_config(silent);
31abe49f MHS	220	}
	221
	222	/**
	223	* Initializes the FPGA for reader-mode (field on), and acquires the samples.
	224	* @return number of bits sampled
	225	**/
24c49d36	226	uint32_t SampleLF(bool printCfg) {
1fbf8956	227	return ReadLF(true, printCfg);
31abe49f MHS	228	}
	229	/**
	230	* Initializes the FPGA for snoop-mode (field off), and acquires the samples.
	231	* @return number of bits sampled
	232	**/
ac2df346	233	uint32_t SnoopLF() {
1fbf8956	234	return ReadLF(false, true);
31abe49f	235	}
ac2df346	236
	237	/**
	238	* acquisition of T55x7 LF signal. Similart to other LF, but adjusted with @marshmellows thresholds
	239	* the data is collected in BigBuf.
	240	**/
94422fa2	241	void doT55x7Acquisition(size_t sample_size) {
ac2df346	242
24c49d36	243	#define T55xx_READ_UPPER_THRESHOLD 128+40 // 60 grph
	244	#define T55xx_READ_LOWER_THRESHOLD 128-40 // -60 grph
	245	#define T55xx_READ_TOL 2
	246
ac2df346	247	uint8_t *dest = BigBuf_get_addr();
	248	uint16_t bufsize = BigBuf_max_traceLen();
	249
94422fa2	250	if ( bufsize > sample_size )
94422fa2	251	bufsize = sample_size;
ac2df346	252
24c49d36	253	uint8_t curSample = 0, lastSample = 0;
24c49d36	254	uint16_t i = 0, skipCnt = 0;
ac2df346	255	bool startFound = false;
ac2df346	256	bool highFound = false;
6426f6ba	257	bool lowFound = false;
24c49d36	258
3f267966	259	while(!BUTTON_PRESS() && !usb_poll_validate_length() && skipCnt < 1000 && (i < bufsize) ) {
1c8fbeb9	260	WDT_HIT();
ac2df346	261	if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
53d5dc64	262	AT91C_BASE_SSC->SSC_THR = 0x43; //43
ac2df346	263	LED_D_ON();
	264	}
	265	if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
1d0ccbe0	266	curSample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
1c8fbeb9	267	LED_D_OFF();
1c8fbeb9	268
94422fa2	269	// skip until the first high sample above threshold
1d0ccbe0	270	if (!startFound && curSample > T55xx_READ_UPPER_THRESHOLD) {
6426f6ba	271	//if (curSample > lastSample)
6426f6ba	272	// lastSample = curSample;
1d0ccbe0	273	highFound = true;
ac2df346	274	} else if (!highFound) {
1d0ccbe0	275	skipCnt++;
ac2df346	276	continue;
ac2df346	277	}
53d5dc64	278	// skip until the first low sample below threshold
6426f6ba	279	if (!startFound && curSample < T55xx_READ_LOWER_THRESHOLD) {
	280	//if (curSample > lastSample)
	281	lastSample = curSample;
	282	lowFound = true;
	283	} else if (!lowFound) {
	284	skipCnt++;
	285	continue;
	286	}
	287
94422fa2	288	// skip until first high samples begin to change
24c49d36	289	if (startFound \|\| curSample > T55xx_READ_LOWER_THRESHOLD + T55xx_READ_TOL){
94422fa2	290	// if just found start - recover last sample
94422fa2	291	if (!startFound) {
6426f6ba	292	dest[i++] = lastSample;
3f267966	293	startFound = true;
94422fa2	294	}
94422fa2	295	// collect samples
1d0ccbe0	296	dest[i++] = curSample;
ac2df346	297	}
	298	}
	299	}
1d0ccbe0	300	}
1d0ccbe0	301