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hw tune: compute Q

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This commit is contained in:
Philippe Teuwen 2020-10-10 00:55:50 +02:00
commit 104377362a
1 changed files with 38 additions and 1 deletions
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39
client/src/cmddata.c
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@ -1694,6 +1694,37 @@ int CmdTuneSamples(const char *Cmd) {
if (package->peak_v > NON_VOLTAGE && package->peak_f > 0)
PrintAndLogEx(SUCCESS, "LF optimal: %5.2f V - %6.2f kHz", (package->peak_v * ANTENNA_ERROR) / 1000.0, LF_DIV2FREQ(package->peak_f));
double vdd = IfPm3Rdv4Fw() ? 9000 : 5400; // Empirical measures in mV
if (package->peak_v > NON_VOLTAGE && package->peak_f > 0) {
// Q measure with Q=f/delta_f
double v_3db_scaled = (double)(package->peak_v * 0.707) / 512; // /512 == >>9
uint32_t s2=0, s4=0;
for (int i = 1; i < 256; i++) {
if ((s2 == 0) && (package->results[i] > v_3db_scaled)) {
s2 = i;
}
if ((s2 != 0) && (package->results[i] < v_3db_scaled)) {
s4 = i;
break;
}
}
if (s4 != 0) { // we got all our points of interest
double a = package->results[s2 - 1];
double b = package->results[s2];
double f1 = LF_DIV2FREQ(s2 - 1 + (v_3db_scaled - a)/(b-a));
double c = package->results[s4 - 1];
double d = package->results[s4];
double f2 = LF_DIV2FREQ(s4 - 1 + (c - v_3db_scaled)/(c-d));
double q = LF_DIV2FREQ(package->peak_f) / (f1 - f2);
PrintAndLogEx(SUCCESS, "Approx. Q factor (*): %.1lf by frequency bandwidth measurement", q);
}
// Q measure with Vlr=Q*(2*Vdd/pi)
double q = (double)package->peak_v * 3.14 / 2 / vdd;
PrintAndLogEx(SUCCESS, "Approx. Q factor (*): %.1lf by peak voltage measurement", q);
}
char judgement[20];
memset(judgement, 0, sizeof(judgement));
// LF evaluation
@ -1713,6 +1744,11 @@ int CmdTuneSamples(const char *Cmd) {
memset(judgement, 0, sizeof(judgement));
if (package->v_hf >= HF_UNUSABLE_V) {
// Q measure with Vlr=Q*(2*Vdd/pi)
double q = (double)package->v_hf * 3.14 / 2 / vdd;
PrintAndLogEx(SUCCESS, "Approx. Q factor (*): %.1lf by peak voltage measurement", q);
}
if (package->v_hf < HF_UNUSABLE_V)
sprintf(judgement, _RED_("UNUSABLE"));
else if (package->v_hf < HF_MARGINAL_V)
@ -1721,6 +1757,7 @@ int CmdTuneSamples(const char *Cmd) {
sprintf(judgement, _GREEN_("OK"));
PrintAndLogEx((package->v_hf < HF_UNUSABLE_V) ? WARNING : SUCCESS, "HF antenna is %s", judgement);
PrintAndLogEx(NORMAL, "\n(*) Q factor must be measured without tag on the antenna");
// graph LF measurements
// even here, these values has 3% error.
@ -1731,7 +1768,7 @@ int CmdTuneSamples(const char *Cmd) {
}
if (test1 > 0) {
PrintAndLogEx(SUCCESS, "\nDisplaying LF tuning graph. Divisor %d is %.2f kHz, %d is %.2f kHz.\n\n",
PrintAndLogEx(SUCCESS, "\nDisplaying LF tuning graph. Divisor %d (blue) is %.2f kHz, %d (red) is %.2f kHz.\n\n",
LF_DIVISOR_134, LF_DIV2FREQ(LF_DIVISOR_134), LF_DIVISOR_125, LF_DIV2FREQ(LF_DIVISOR_125));
GraphTraceLen = 256;
CursorCPos = LF_DIVISOR_125;