From 3b692427ac2585148be70b2dd3363a8ad1a95fe0 Mon Sep 17 00:00:00 2001 From: pwpiwi Date: Tue, 3 Feb 2015 07:21:57 +0100 Subject: [PATCH] Bugfix hw tune, hf tune: voltage measures were VERY wrong Modified hw detectreader: display reader field strength in mV units and to be less phony --- armsrc/appmain.c | 95 ++++++++++++++++++++++++++++-------------------- armsrc/apps.h | 4 ++ 2 files changed, 60 insertions(+), 39 deletions(-) diff --git a/armsrc/appmain.c b/armsrc/appmain.c index cb1b9f73..189f9d7a 100644 --- a/armsrc/appmain.c +++ b/armsrc/appmain.c @@ -135,12 +135,25 @@ static int ReadAdc(int ch) 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]; @@ -183,9 +196,7 @@ void MeasureAntennaTuning(void) 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 @@ -205,11 +216,9 @@ void MeasureAntennaTuning(void) 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(); @@ -222,19 +231,21 @@ void MeasureAntennaTuningHf(void) 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); + } @@ -512,26 +523,32 @@ static const int LIGHT_LEN = sizeof(LIGHT_SCHEME)/sizeof(LIGHT_SCHEME[0]); 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; } @@ -554,38 +571,38 @@ void ListenReaderField(int limit) 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; } } diff --git a/armsrc/apps.h b/armsrc/apps.h index 58a2a621..a15d8b81 100644 --- a/armsrc/apps.h +++ b/armsrc/apps.h @@ -38,6 +38,10 @@ void DbpString(char *str); void Dbprintf(const char *fmt, ...); void Dbhexdump(int len, uint8_t *d, bool bAsci); +// ADC Vref = 3300mV, and an (10M+1M):1M voltage divider on the HF input can measure voltages up to 36300 mV +#define MAX_ADC_HF_VOLTAGE 36300 +// ADC Vref = 3300mV, and an (10000k+240k):240k voltage divider on the LF input can measure voltages up to 140800 mV +#define MAX_ADC_LF_VOLTAGE 140800 int AvgAdc(int ch); void ToSendStuffBit(int b); -- 2.39.2