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dynamic creation of spectrum analyzer with parameters
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@ka9q
ka9q committed Apr 18, 2023
1 parent 0fc1936 commit 9639148
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Showing 3 changed files with 78 additions and 47 deletions.
96 changes: 61 additions & 35 deletions powers.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -31,22 +31,38 @@ char Locale[256] = "en_US.UTF-8";
char Iface[1024]; // Multicast interface to talk to front end
int Status_fd,Ctl_fd;

int dump_powers(float *power,int npower,uint64_t *time,double *freq,double *bin_bw,int32_t const ssrc,uint8_t const * const buffer,int length);
int extract_powers(float *power,int npower,uint64_t *time,double *freq,double *bin_bw,int32_t const ssrc,uint8_t const * const buffer,int length);

int main(int argc,char *argv[]){
App_path = argv[0];
int count = -1; // Number of updates. -1 means infinite
int count = 1; // Number of updates. -1 means infinite
float interval = 5; // Period between updates, sec
float frequency = 0;
int bins = 0;
float bin_bw = 0;
float tc = 0;
{
int c;
while((c = getopt(argc,argv,"c:i:vs:")) != -1){
while((c = getopt(argc,argv,"f:w:b:c:i:t:vs:")) != -1){
switch(c){
case 'f':
frequency = strtof(optarg,NULL);
break;
case 'w':
bin_bw = strtof(optarg,NULL);
break;
case 'b':
bins = strtol(optarg,NULL,0);
break;
case 'c':
count = strtol(optarg,NULL,0);
break;
case 'i':
interval = strtof(optarg,NULL);
break;
case 't':
tc = strtof(optarg,NULL);
break;
case 'v':
Verbose++;
break;
Expand All @@ -71,7 +87,7 @@ int main(int argc,char *argv[]){
// Dummy filter

if(argc <= optind){
fprintf(stderr,"Usage: %s -s ssrc [-v] [-i interval] [-c count] mcast_addr\n",App_path);
fprintf(stderr,"Usage: %s [-v] -s ssrc [-f freq] [-w bin_bw] [-b bins] [-t time_constant] [-c count [-i interval]] mcast_addr\n",App_path);
exit(1);

}
Expand All @@ -86,18 +102,39 @@ int main(int argc,char *argv[]){
fprintf(stderr,"connect to mcast control failed\n");
exit(1);
}


// Send command to set up the channel?? Or do in a separate command? We'd like to reuse the same demod & ssrc,
// which is hard to do in one command, as we'd have to stash the ssrc somewhere.
while(true){
uint32_t tag = send_poll(Ctl_fd,Ssrc);
uint8_t buffer[8192];
uint8_t *bp = buffer;
*bp++ = 1; // Command

encode_int(&bp,OUTPUT_SSRC,Ssrc);
uint32_t tag = random();
encode_int(&bp,COMMAND_TAG,tag);
encode_int(&bp,DEMOD_TYPE,SPECT_DEMOD);
if(frequency != 0)
encode_float(&bp,RADIO_FREQUENCY,frequency);
if(bins != 0)
encode_int(&bp,BIN_COUNT,bins);
if(bin_bw != 0)
encode_float(&bp,NONCOHERENT_BIN_BW,bin_bw);
if(tc != 0)
encode_float(&bp,INTEGRATE_TC,tc);

encode_eol(&bp);
int const command_len = bp - buffer;
if(send(Ctl_fd, buffer, command_len, 0) != command_len){
perror("command send");
usleep(1000000);
goto again;
}
// The deadline starts at 1 sec after a poll
int64_t deadline = gps_time_ns() + BILLION;

int length = 0;
uint8_t buffer[8192];
while(true){

do {
// Wait for a reply to our query
// ignore all packets on group without changing deadline
fd_set fdset;
Expand All @@ -121,28 +158,19 @@ int main(int argc,char *argv[]){
socklen_t ssize = sizeof(Metadata_source_address);
length = recvfrom(Status_fd,buffer,sizeof(buffer),0,(struct sockaddr *)&Metadata_source_address,&ssize);

// Ignore our own command packets
if(length < 2 || buffer[0] != 0)
continue; // Wait for another one
if(Ssrc != get_ssrc(buffer+1,length-1))
continue; // Not the droid we're looking for; wait for another one

// Ignore invalid packets, command packets, packets re other SSRCs and packets not in response to our polls
// Should we insist on the same command tag, or accept any "recent" status packet, e.g., triggered by the control program?
// This is needed because initial delays in joining multicast groups produce bursts of buffered responses; investigate this
if(tag != get_tag(buffer+1,length-1))
continue; // Also not the droid we're looking for.
// This is needed because an initial delay in joining multicast groups produces a burst of buffered responses; investigate this
} while(length < 2 || buffer[0] != 0 || Ssrc != get_ssrc(buffer+1,length-1) || tag != get_tag(buffer+1,length-1));

break;
}
float powers[65536];
uint64_t time;
double freq;
double bin_bw;
double r_freq;
double r_bin_bw;

int npower = dump_powers(powers,sizeof(powers) / sizeof (powers[0]), &time,&freq,&bin_bw,Ssrc,buffer+1,length-1);
int npower = extract_powers(powers,sizeof(powers) / sizeof (powers[0]), &time,&r_freq,&r_bin_bw,Ssrc,buffer+1,length-1);
if(npower < 0){
printf("Invalid response, length %d\n",npower);

continue; // Invalid for some reason
}
// Note from VK5QI:
Expand All @@ -158,21 +186,21 @@ int main(int argc,char *argv[]){
// npower odd: emit N/2+1....N-1 0....N/2 (division truncating to integer)
// npower even: emit N/2....N-1 0....N/2-1
int const first_neg_bin = (npower + 1)/2; // round up, e.g., 64->32, 65 -> 33, 66 -> 33
float base = freq - bin_bw * (npower/2); // integer truncation (round down), e.g., 64-> 32, 65 -> 32
float base = r_freq - r_bin_bw * (npower/2); // integer truncation (round down), e.g., 64-> 32, 65 -> 32
printf(" %.0f, %.0f, %.0f, %d,",
base, base + bin_bw * (npower-1), bin_bw, npower);
base, base + r_bin_bw * (npower-1), r_bin_bw, npower);

#if TESTING
// Frequencies below center
printf("\n");
for(int i=first_neg_bin ; i < npower; i++){
printf("%d %f %.1f\n",i,base,(powers[i] == 0) ? -100.0 : 10*log10(powers[i]));
base += bin_bw;
base += r_bin_bw;
}
// Frequencies above center
for(int i=0; i < first_neg_bin; i++){
printf("%d %f %.1f\n",i,base,(powers[i] == 0) ? -100.0 : 10*log10(powers[i]));
base += bin_bw;
base += r_bin_bw;
}
#else
for(int i= first_neg_bin; i < npower; i++)
Expand All @@ -182,22 +210,20 @@ int main(int argc,char *argv[]){
printf(" %.1f,",(powers[i] == 0) ? -100.0 : 10*log10(powers[i]));
#endif
printf("\n");
if(--count == 0)
break;

// need to add randomized wait and avoidance of poll if response elicited by other poller (eg., control) comes in first
// And if we decide to use those responses (currently blocked by command tag check)
usleep((useconds_t)(interval * 1e6));

if(count == -1)
continue;
count--;
if(count == 0)
break;
again:;
}
exit(0);
}

// Decode only those status fields relevant to spectrum measurement
// Return number of bins
int dump_powers(float *power,int npower,uint64_t *time,double *freq,double *bin_bw,int32_t const ssrc,uint8_t const * const buffer,int length){
int extract_powers(float *power,int npower,uint64_t *time,double *freq,double *bin_bw,int32_t const ssrc,uint8_t const * const buffer,int length){
#if 0 // use later
double l_lo1 = 0,l_lo2 = 0;
#endif
Expand Down
25 changes: 16 additions & 9 deletions radio_status.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -137,8 +137,8 @@ static int send_radio_status(struct frontend const *frontend,struct demod const

// with SSRC selection, should scan entire command for our SSRC before we execute any of it
static int decode_radio_commands(struct demod *demod,uint8_t const *buffer,int length){
int restart_needed = 0;
int new_filter_needed = 0;
bool restart_needed = false;
bool new_filter_needed = false;

uint8_t const *cp = buffer;
while(cp - buffer < length){
Expand Down Expand Up @@ -173,15 +173,18 @@ static int decode_radio_commands(struct demod *demod,uint8_t const *buffer,int l
int new_sample_rate = decode_int(cp,optlen);
if(new_sample_rate != demod->output.samprate){
demod->output.samprate = new_sample_rate;
restart_needed = 1;
restart_needed = true;
}
}
break;
case RADIO_FREQUENCY: // Hz
{
double const f = fabs(decode_double(cp,optlen));
if(isfinite(f))
if(isfinite(f)){
set_freq(demod,f);
if(demod->demod_type == SPECT_DEMOD)
restart_needed = true; // Easier than trying to handle it inline
}
}
break;
case FIRST_LO_FREQUENCY:
Expand Down Expand Up @@ -259,7 +262,7 @@ static int decode_radio_commands(struct demod *demod,uint8_t const *buffer,int l
new_filter_needed = 1;

if(demod->demod_type != old_type || demod->output.samprate != old_samprate)
restart_needed = 1; // demod changed, ask for a restart
restart_needed = true; // demod changed, ask for a restart
}
}
break;
Expand All @@ -268,7 +271,7 @@ static int decode_radio_commands(struct demod *demod,uint8_t const *buffer,int l
enum demod_type const i = decode_int(cp,optlen);
if(i >= 0 && i < Ndemod && i != demod->demod_type){
demod->demod_type = i;
restart_needed = 1;
restart_needed = true;
}
}
break;
Expand Down Expand Up @@ -356,22 +359,26 @@ static int decode_radio_commands(struct demod *demod,uint8_t const *buffer,int l
case NONCOHERENT_BIN_BW:
{
float const x = decode_float(cp,optlen);
if(!isnan(x))
if(!isnan(x) && x != demod->spectrum.bin_bw){
demod->spectrum.bin_bw = x;
restart_needed = true;
}
}
break;
case BIN_COUNT:
{
int const x = decode_int(cp,optlen);
if(x > 0)
if(x > 0 && x != demod->spectrum.bin_count){
demod->spectrum.bin_count = x;
restart_needed = true;
}
}
break;
case INTEGRATE_TC:
{
float const x = decode_float(cp,optlen);
if(!isnan(x))
demod->spectrum.integrate_tc = x;
demod->spectrum.integrate_tc = x; // No restart needed for this parameter
}
break;
default:
Expand Down
4 changes: 1 addition & 3 deletions spectrum.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -68,7 +68,6 @@ void *demod_spectrum(void *arg){

set_freq(demod,demod->tune.freq); // retune front end if needed to cover requested bandwidth

float f = demod->tune.freq; // Cache radio frequency
float tc = 0; // time constant cache, let it be set in the first iteration
float smooth = 1;
// Do first update with smooth == 1 so we don't have to wait for an initial exponential rise
Expand All @@ -78,7 +77,7 @@ void *demod_spectrum(void *arg){
break; // received terminate

// If a user parameter has changed, restart the integrators
if(demod->spectrum.integrate_tc != tc || f != demod->tune.freq)
if(demod->spectrum.integrate_tc != tc)
smooth = 1;

int binp = 0;
Expand All @@ -97,7 +96,6 @@ void *demod_spectrum(void *arg){
demod->spectrum.integrate_tc = 5; // Force reasonable value of 5 sec

// Update cached copies, recalculate smoothing param
f = demod->tune.freq;
tc = demod->spectrum.integrate_tc;
// https://en.wikipedia.org/wiki/Exponential_smoothing#Time constant
// smooth = 1 - exp(-blocktime/tc)
Expand Down

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