#endif
// Craig Young - 14a stand-alone code
-#ifdef WITH_ISO14443a_StandAlone
+#ifdef WITH_ISO14443a
#include "iso14443a.h"
#endif
// return that.
//-----------------------------------------------------------------------------
static int ReadAdc(int ch)
-{
- uint32_t d;
-
- AT91C_BASE_ADC->ADC_CR = AT91C_ADC_SWRST;
- AT91C_BASE_ADC->ADC_MR =
- ADC_MODE_PRESCALE(63 /* was 32 */) | // ADC_CLK = MCK / ((63+1) * 2) = 48MHz / 128 = 375kHz
- ADC_MODE_STARTUP_TIME(1 /* was 16 */) | // Startup Time = (1+1) * 8 / ADC_CLK = 16 / 375kHz = 42,7us Note: must be > 20us
- ADC_MODE_SAMPLE_HOLD_TIME(15 /* was 8 */); // Sample & Hold Time SHTIM = 15 / ADC_CLK = 15 / 375kHz = 40us
-
+{
// Note: ADC_MODE_PRESCALE and ADC_MODE_SAMPLE_HOLD_TIME are set to the maximum allowed value.
- // Both AMPL_LO and AMPL_HI are very high impedance (10MOhm) outputs, the input capacitance of the ADC is 12pF (typical). This results in a time constant
- // of RC = 10MOhm * 12pF = 120us. Even after the maximum configurable sample&hold time of 40us the input capacitor will not be fully charged.
+ // AMPL_HI is are high impedance (10MOhm || 1MOhm) output, the input capacitance of the ADC is 12pF (typical). This results in a time constant
+ // of RC = (0.91MOhm) * 12pF = 10.9us. Even after the maximum configurable sample&hold time of 40us the input capacitor will not be fully charged.
//
// The maths are:
// If there is a voltage v_in at the input, the voltage v_cap at the capacitor (this is what we are measuring) will be
//
- // v_cap = v_in * (1 - exp(-RC/SHTIM)) = v_in * (1 - exp(-3)) = v_in * 0,95 (i.e. an error of 5%)
- //
- // Note: with the "historic" values in the comments above, the error was 34% !!!
-
- AT91C_BASE_ADC->ADC_CHER = ADC_CHANNEL(ch);
+ // v_cap = v_in * (1 - exp(-SHTIM/RC)) = v_in * (1 - exp(-40us/10.9us)) = v_in * 0,97 (i.e. an error of 3%)
- AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START;
+ AT91C_BASE_ADC->ADC_CR = AT91C_ADC_SWRST;
+ AT91C_BASE_ADC->ADC_MR =
+ ADC_MODE_PRESCALE(63) | // ADC_CLK = MCK / ((63+1) * 2) = 48MHz / 128 = 375kHz
+ ADC_MODE_STARTUP_TIME(1) | // Startup Time = (1+1) * 8 / ADC_CLK = 16 / 375kHz = 42,7us Note: must be > 20us
+ ADC_MODE_SAMPLE_HOLD_TIME(15); // Sample & Hold Time SHTIM = 15 / ADC_CLK = 15 / 375kHz = 40us
- while(!(AT91C_BASE_ADC->ADC_SR & ADC_END_OF_CONVERSION(ch)))
- ;
- d = AT91C_BASE_ADC->ADC_CDR[ch];
+ AT91C_BASE_ADC->ADC_CHER = ADC_CHANNEL(ch);
+ AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START;
- return d;
+ while(!(AT91C_BASE_ADC->ADC_SR & ADC_END_OF_CONVERSION(ch))) {};
+
+ return AT91C_BASE_ADC->ADC_CDR[ch];
}
int AvgAdc(int ch) // was static - merlok
FpgaDownloadAndGo(FPGA_BITSTREAM_LF);
FpgaWriteConfWord(FPGA_MAJOR_MODE_LF_ADC | FPGA_LF_ADC_READER_FIELD);
+ SpinDelay(50);
+
for (i=255; i>=19; i--) {
WDT_HIT();
FpgaSendCommand(FPGA_CMD_SET_DIVISOR, i);
if (i==95) *vLf125 = adcval; // voltage at 125Khz
if (i==89) *vLf134 = adcval; // voltage at 134Khz
- LF_Results[i] = adcval>>8; // scale int to fit in byte for graphing purposes
+ LF_Results[i] = adcval >> 9; // scale int to fit in byte for graphing purposes
if(LF_Results[i] > peak) {
*peakv = adcval;
peak = LF_Results[i];
}
}
- cmd_send(CMD_MEASURED_ANTENNA_TUNING, vLf125 | (vLf134<<16), vHf, peakf | (peakv<<16), LF_Results, 256);
+ cmd_send(CMD_MEASURED_ANTENNA_TUNING, vLf125>>1 | (vLf134>>1<<16), vHf, peakf | (peakv>>1<<16), LF_Results, 256);
FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
LED_B_OFF();
return;