rpitx/csdr
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

bpsk_costas_loop_cc function added to csdr

Browse source
This commit is contained in:
ha7ilm 2017-03-31 21:23:07 +02:00
parent 7590dd78ab
commit ca578ea4bc
3 changed files with 52 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

25
csdr.c
View file

@ -131,6 +131,7 @@ char usage[]=
" psk_modulator_u8_c <n_psk>\n"
" psk31_interpolate_sine_cc\n"
" duplicate_samples_ntimes_u8_u8 <sample_size_bytes> <ntimes>\n"
" bpsk_costas_loop_cc <samples_per_bits>\n"
" ?<search_the_function_list>\n"
" \n"
;
@ -2396,7 +2397,7 @@ int main(int argc, char *argv[])
fwrite(output_buffer, sizeof(complexf), state.output_size, stdout);
fflush(stdout);
TRY_YIELD;
fprintf(stderr, "state.input_processed = %d\n", state.input_processed);
//fprintf(stderr, "state.input_processed = %d\n", state.input_processed);
memmove((complexf*)input_buffer,((complexf*)input_buffer)+state.input_processed,(the_bufsize-state.input_processed)*sizeof(complexf)); //memmove lets the source and destination overlap
fread(((complexf*)input_buffer)+(the_bufsize-state.input_processed), sizeof(complexf), state.input_processed, stdin);
//fprintf(stderr,"iskip=%d state.output_size=%d start=%x target=%x skipcount=%x \n",state.input_processed,state.output_size,input_buffer, ((complexf*)input_buffer)+(BIG_BUFSIZE-state.input_processed),(BIG_BUFSIZE-state.input_processed));
@ -2575,6 +2576,28 @@ int main(int argc, char *argv[])
}
}
if(!strcmp(argv[1],"bpsk_costas_loop_cc")) //<samples_per_bits>
{
float samples_per_bits;
if(argc<=2) return badsyntax("need required parameter (samples_per_bits)");
sscanf(argv[2],"%f",&samples_per_bits);
if(samples_per_bits<=0) badsyntax("samples_per_bits should be >= 0");
bpsk_costas_loop_state_t state = init_bpsk_costas_loop_cc(samples_per_bits);
if(!initialize_buffers()) return -2;
sendbufsize(the_bufsize);
for(;;)
{
FEOF_CHECK;
FREAD_C;
bpsk_costas_loop_cc((complexf*)input_buffer, (complexf*)output_buffer, the_bufsize, &state);
FWRITE_C;
TRY_YIELD;
}
}
if(!strcmp(argv[1],"none"))
{
return 0;

29
libcsdr.c
View file

@ -1907,34 +1907,35 @@ char* timing_recovery_get_string_from_algorithm(timing_recovery_algorithm_t algo
return "INVALID";
}
typedef struct bpsk_costas_loop_state_s
{
float rc_filter_alpha;
float vco_phase_addition_multiplier;
float vco_phase;
float last_lpfi_output;
float last_lpfq_output;
} bpsk_costas_loop_state_t;
void init_bpsk_costas_loop_cc(bpsk_costas_loop_state_t* state, float samples_per_bits)
bpsk_costas_loop_state_t init_bpsk_costas_loop_cc(float samples_per_bits)
{
state->vco_phase = 0;
bpsk_costas_loop_state_t state;
state.vco_phase = 0;
float virtual_sampling_rate = 10000;
float virtual_data_rate = virtual_sampling_rate / samples_per_bits;
fprintf(stderr, "virtual_sampling_rate = %g, virtual_data_rate = %g\n", virtual_sampling_rate, virtual_data_rate);
float rc_filter_cutoff = virtual_data_rate/2;
float rc_filter_rc = 1/(2*M_PI*rc_filter_cutoff); //as of Equation 24 in Feigin
float virtual_sampling_dt = 1.0/virtual_sampling_rate;
state->rc_filter_alpha = virtual_sampling_dt/(rc_filter_rc+virtual_sampling_dt); //https://en.wikipedia.org/wiki/Low-pass_filter
fprintf(stderr, "rc_filter_cutoff = %g, rc_filter_rc = %g, virtual_sampling_dt = %g\n",
rc_filter_cutoff, rc_filter_rc, virtual_sampling_dt);
state.rc_filter_alpha = virtual_sampling_dt/(rc_filter_rc+virtual_sampling_dt); //https://en.wikipedia.org/wiki/Low-pass_filter
float rc_filter_omega_cutoff = 2*M_PI*rc_filter_cutoff;
state->vco_phase_addition_multiplier = 8*rc_filter_omega_cutoff; //as of Equation 25 in Feigin, assuming input signal amplitude of 1 (to 1V) and (state->vco_phase_addition_multiplier*<vco_input>), a value in radians, will be added to the vco_phase directly.
state.vco_phase_addition_multiplier = 8*rc_filter_omega_cutoff; //as of Equation 25 in Feigin, assuming input signal amplitude of 1 (to 1V) and (state.vco_phase_addition_multiplier*<vco_input>), a value in radians, will be added to the vco_phase directly.
fprintf(stderr, "rc_filter_alpha = %g, rc_filter_omega_cutoff = %g, vco_phase_addition_multiplier = %g\n",
state.rc_filter_alpha, rc_filter_omega_cutoff, state.vco_phase_addition_multiplier);
return state;
}
void bpsk_costas_loop_cc(complexf* input, complexf* output, int input_size, bpsk_costas_loop_state_t* state)
{
int debug = 0;
if(debug) fprintf(stderr, "costas:\n");
for(int i=0;i<input_size;i++)
{
float input_phase = atan2(input[i].q, input[i].i);
float input_and_vco_mixed_phase = input_phase - state->vco_phase;
if(debug) fprintf(stderr, "%g | %g\n", input_and_vco_mixed_phase, input_phase), debug--;
complexf input_and_vco_mixed_sample;
e_powj(&input_and_vco_mixed_sample, input_and_vco_mixed_phase);
float loop_output_i =
@ -1947,6 +1948,8 @@ void bpsk_costas_loop_cc(complexf* input, complexf* output, int input_size, bpsk
state->vco_phase += vco_phase_addition;
while(state->vco_phase>PI) state->vco_phase-=2*PI;
while(state->vco_phase<-PI) state->vco_phase+=2*PI;
output[i].i = loop_output_i;
output[i].q = loop_output_q;
}
}

12
libcsdr.h
View file

@ -323,3 +323,15 @@ complexf psk31_interpolate_sine_cc(complexf* input, complexf* output, int input_
void pack_bits_8to1_u8_u8(unsigned char* input, unsigned char* output, int input_size);
void psk31_varicode_encoder_u8_u8(unsigned char* input, unsigned char* output, int input_size, int output_max_size, int* input_processed, int* output_size);
unsigned char differential_codec(unsigned char* input, unsigned char* output, int input_size, int encode, unsigned char state);
typedef struct bpsk_costas_loop_state_s
{
float rc_filter_alpha;
float vco_phase_addition_multiplier;
float vco_phase;
float last_lpfi_output;
float last_lpfq_output;
} bpsk_costas_loop_state_t;
bpsk_costas_loop_state_t init_bpsk_costas_loop_cc(float samples_per_bits);
void bpsk_costas_loop_cc(complexf* input, complexf* output, int input_size, bpsk_costas_loop_state_t* state);