proxmark3/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;
			}
		}
	}
}