AT91C_BASE_ADC->ADC_CR = AT91C_ADC_SWRST;
AT91C_BASE_ADC->ADC_MR =
- ADC_MODE_PRESCALE(32) |
- ADC_MODE_STARTUP_TIME(16) |
- ADC_MODE_SAMPLE_HOLD_TIME(8);
+ 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.
+ //
+ // 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);
AT91C_BASE_ADC->ADC_CR = AT91C_ADC_START;
+
while(!(AT91C_BASE_ADC->ADC_SR & ADC_END_OF_CONVERSION(ch)))
;
d = AT91C_BASE_ADC->ADC_CDR[ch];
WDT_HIT();
FpgaSendCommand(FPGA_CMD_SET_DIVISOR, i);
SpinDelay(20);
- // Vref = 3.3V, and a 10000:240 voltage divider on the input
- // can measure voltages up to 137500 mV
- adcval = ((137500 * AvgAdc(ADC_CHAN_LF)) >> 10);
+ adcval = ((MAX_ADC_LF_VOLTAGE * AvgAdc(ADC_CHAN_LF)) >> 10);
if (i==95) vLf125 = adcval; // voltage at 125Khz
if (i==89) vLf134 = adcval; // voltage at 134Khz
FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
SpinDelay(20);
- // Vref = 3300mV, and an 10:1 voltage divider on the input
- // can measure voltages up to 33000 mV
- vHf = (33000 * AvgAdc(ADC_CHAN_HF)) >> 10;
+ vHf = (MAX_ADC_HF_VOLTAGE * AvgAdc(ADC_CHAN_HF)) >> 10;
- cmd_send(CMD_MEASURED_ANTENNA_TUNING,vLf125|(vLf134<<16),vHf,peakf|(peakv<<16),LF_Results,256);
+ cmd_send(CMD_MEASURED_ANTENNA_TUNING, vLf125 | (vLf134<<16), vHf, peakf | (peakv<<16), LF_Results, 256);
FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
LED_A_OFF();
LED_B_OFF();
DbpString("Measuring HF antenna, press button to exit");
+ // Let the FPGA drive the high-frequency antenna around 13.56 MHz.
+ FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
+
for (;;) {
- // Let the FPGA drive the high-frequency antenna around 13.56 MHz.
- FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
- FpgaWriteConfWord(FPGA_MAJOR_MODE_HF_READER_RX_XCORR);
SpinDelay(20);
- // Vref = 3300mV, and an 10:1 voltage divider on the input
- // can measure voltages up to 33000 mV
- vHf = (33000 * AvgAdc(ADC_CHAN_HF)) >> 10;
+ vHf = (MAX_ADC_HF_VOLTAGE * AvgAdc(ADC_CHAN_HF)) >> 10;
Dbprintf("%d mV",vHf);
if (BUTTON_PRESS()) break;
}
DbpString("cancelled");
+
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
+
}
void ListenReaderField(int limit)
{
- int lf_av, lf_av_new, lf_baseline= 0, lf_count= 0, lf_max;
- int hf_av, hf_av_new, hf_baseline= 0, hf_count= 0, hf_max;
+ int lf_av, lf_av_new, lf_baseline= 0, lf_max;
+ int hf_av, hf_av_new, hf_baseline= 0, hf_max;
int mode=1, display_val, display_max, i;
-#define LF_ONLY 1
-#define HF_ONLY 2
+#define LF_ONLY 1
+#define HF_ONLY 2
+#define REPORT_CHANGE 10 // report new values only if they have changed at least by REPORT_CHANGE
+
+
+ // switch off FPGA - we don't want to measure our own signal
+ FpgaDownloadAndGo(FPGA_BITSTREAM_HF);
+ FpgaWriteConfWord(FPGA_MAJOR_MODE_OFF);
LEDsoff();
- lf_av=lf_max=ReadAdc(ADC_CHAN_LF);
+ lf_av = lf_max = AvgAdc(ADC_CHAN_LF);
if(limit != HF_ONLY) {
- Dbprintf("LF 125/134 Baseline: %d", lf_av);
+ Dbprintf("LF 125/134kHz Baseline: %dmV", (MAX_ADC_LF_VOLTAGE * lf_av) >> 10);
lf_baseline = lf_av;
}
- hf_av=hf_max=ReadAdc(ADC_CHAN_HF);
+ hf_av = hf_max = AvgAdc(ADC_CHAN_HF);
if (limit != LF_ONLY) {
- Dbprintf("HF 13.56 Baseline: %d", hf_av);
+ Dbprintf("HF 13.56MHz Baseline: %dmV", (MAX_ADC_HF_VOLTAGE * hf_av) >> 10);
hf_baseline = hf_av;
}
WDT_HIT();
if (limit != HF_ONLY) {
- if(mode==1) {
- if (abs(lf_av - lf_baseline) > 10) LED_D_ON();
- else LED_D_OFF();
+ if(mode == 1) {
+ if (abs(lf_av - lf_baseline) > REPORT_CHANGE)
+ LED_D_ON();
+ else
+ LED_D_OFF();
}
- ++lf_count;
- lf_av_new= ReadAdc(ADC_CHAN_LF);
+ lf_av_new = AvgAdc(ADC_CHAN_LF);
// see if there's a significant change
- if(abs(lf_av - lf_av_new) > 10) {
- Dbprintf("LF 125/134 Field Change: %x %x %x", lf_av, lf_av_new, lf_count);
+ if(abs(lf_av - lf_av_new) > REPORT_CHANGE) {
+ Dbprintf("LF 125/134kHz Field Change: %5dmV", (MAX_ADC_LF_VOLTAGE * lf_av_new) >> 10);
lf_av = lf_av_new;
if (lf_av > lf_max)
lf_max = lf_av;
- lf_count= 0;
}
}
if (limit != LF_ONLY) {
if (mode == 1){
- if (abs(hf_av - hf_baseline) > 10) LED_B_ON();
- else LED_B_OFF();
+ if (abs(hf_av - hf_baseline) > REPORT_CHANGE)
+ LED_B_ON();
+ else
+ LED_B_OFF();
}
- ++hf_count;
- hf_av_new= ReadAdc(ADC_CHAN_HF);
+ hf_av_new = AvgAdc(ADC_CHAN_HF);
// see if there's a significant change
- if(abs(hf_av - hf_av_new) > 10) {
- Dbprintf("HF 13.56 Field Change: %x %x %x", hf_av, hf_av_new, hf_count);
+ if(abs(hf_av - hf_av_new) > REPORT_CHANGE) {
+ Dbprintf("HF 13.56MHz Field Change: %5dmV", (MAX_ADC_HF_VOLTAGE * hf_av_new) >> 10);
hf_av = hf_av_new;
if (hf_av > hf_max)
hf_max = hf_av;
- hf_count= 0;
}
}
projects / proxmark3-svn / blobdiff