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QortalOS Brooklyn for Raspberry Pi 4
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Brooklyn/IPoverVHF/tx/rpitx_fsk.cpp

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/*
rpitx_fsk.cpp
David Rowe July 2020
FSK modulates an input bit stream using rpitx.
TODO:
[X] option for packed/unpacked byte input data
[ ] Fix operation at Rs<200, at present we can't detect any packets at Rs=100
[ ] test with other LDPC codes
+ high rate codes are of interest, big gains for small overhead
*/
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <math.h>
#include <signal.h>
#include <getopt.h>
#include <unistd.h>
#include <fcntl.h>
#include "../librpitx/src/librpitx.h"
#include "ldpc_codes.h"
#include "freedv_api.h"
#define MAX_CHAR 256
#define FIFO_SIZE 100
// Functions to build FSK_LDPC frame. Not normally exposed by FreeDV API
extern "C" {
int freedv_tx_fsk_ldpc_bits_per_frame(struct freedv *f);
void freedv_tx_fsk_ldpc_framer(struct freedv *f, uint8_t frame[], uint8_t payload_data[]);
void ofdm_generate_payload_data_bits(uint8_t payload_data_bits[], int n);
unsigned short freedv_gen_crc16(unsigned char* data_p, int length);
void freedv_pack(unsigned char *bytes, unsigned char *bits, int nbits);
void freedv_unpack(unsigned char *bits, unsigned char *bytes, int nbits);
}
bool running=true;
static int terminate_calls = 0;
ngfmdmasync *fmmod = NULL;
float initial_frequency = 0.0;
// Signals like Ctrl-C or segfaults get handled here
static void terminate(int num) {
terminate_calls++;
running=false;
fprintf(stderr,"Caught signal %d - Terminating\n", num);
if (terminate_calls >= 5) {
fprintf(stderr, "Too many signals - finishing....\n");
fmmod->clkgpio::print_clock_tree();
// make sure TX is off if we have to abort
if (fmmod) delete fmmod;
exit(1);
}
}
/* Use the Linux /sys/class/gpio system to access the RPis GPIOs */
void sys_gpio(const char filename[], const char s[]) {
FILE *fgpio = fopen(filename, "wt");
//fprintf(stderr,"%s %s\n",filename, s);
if (fgpio == NULL) {
fprintf(stderr, "\nProblem opening %s\n", filename);
exit(1);
}
fprintf(fgpio,"%s",s);
fclose(fgpio);
}
// calculate and insert CRC in the last 16 bits of (unpacked) data_bits[]
void calculate_and_insert_crc(uint8_t data_bits[], int data_bits_per_frame) {
assert((data_bits_per_frame % 8) == 0);
int data_bytes_per_frame = data_bits_per_frame / 8;
uint8_t data_bytes[data_bytes_per_frame];
freedv_pack(data_bytes, data_bits, data_bits_per_frame-16);
uint16_t crc16 = freedv_gen_crc16(data_bytes, data_bytes_per_frame-2);
uint8_t crc16_bytes[] = { (uint8_t)(crc16 >> 8), (uint8_t)(crc16 & 0xff) };
freedv_unpack(data_bits+data_bits_per_frame-16, crc16_bytes, 16);
}
/* Sanity check PLLC. During development this was getting modified outside of rpitx.
Fix is to add "force_turbo=1" to the end of /boot/config.txt */
#define PLLC_CTRL (0x1120 / 4) // from libpitx/src/gpio.h
float initial_pllc_freq() {
volatile uint32_t *gpioreg = fmmod->clkgpio::gpioreg;
return 19.2 * 1E6 * ((float)(gpioreg[PLLC_CTRL] & 0x3ff) + ((float)gpioreg[PLLC_FRAC]) / ((float)(1 << 20)));
}
void check_pllc() {
volatile uint32_t *gpioreg = fmmod->clkgpio::gpioreg;
float current_freq = 19.2 * 1E6 * ((float)(gpioreg[PLLC_CTRL] & 0x3ff) + ((float)gpioreg[PLLC_FRAC]) / ((float)(1 << 20)));
float delta = fabs(current_freq - initial_frequency)/initial_frequency;
if (delta > 0.01) {
fprintf(stderr, "PLLC PDIV=%d NDIV=%d FRAC=%d ", (gpioreg[PLLC_CTRL] >> 12)&0x7, gpioreg[PLLC_CTRL] & 0x3ff, gpioreg[PLLC_FRAC]);
fprintf(stderr, " %f MHz\n", 19.2 * ((float)(gpioreg[PLLC_CTRL] & 0x3ff) + ((float)gpioreg[PLLC_FRAC]) / ((float)(1 << 20))));
fprintf(stderr, "\nPLLC getting modified outside of rpitx! Add \"force_turbo=1\" to the end of /boot/config.txt\n");
delete fmmod;
exit(1);
}
}
// My attempt at a function to send samples to the DMA circular
// buffer. Not sure if this is any better than ngfmdamsync functions!
// Interesting area for further work.
int SetFrequencySampleNonBlocking(ngfmdmasync *fmmod, float Frequency)
{
int Index = fmmod->GetUserMemIndex();
if (Index == -1) {
return -1;
} else {
fmmod->sampletab[Index]=(0x5A<<24)|fmmod->GetMasterFrac(Frequency);
fmmod->PushSample(Index);
return 0;
}
}
// FSK Modulate and Tx a frame of bits
void modulate_frame(ngfmdmasync *fmmod, float shiftHz, int m, uint8_t tx_frame[], int bits_per_frame) {
assert(fmmod != NULL);
for(int bit_i=0; bit_i<bits_per_frame;) {
/* generate the symbol number from the bit stream,
e.g. 0,1 for 2FSK, 0,1,2,3 for 4FSK */
int sym = 0;
for(int i=m; i>>=1; ) {
uint8_t bit = tx_frame[bit_i] & 0x1;
sym = (sym<<1)|bit;
bit_i++;
}
float VCOfreqHz = shiftHz*sym;
while (SetFrequencySampleNonBlocking(fmmod,VCOfreqHz)) usleep(100);
}
}
int main(int argc, char **argv)
{
for (int i = 0; i < 64; i++) {
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = terminate;
sigaction(i, &sa, NULL);
}
FILE *fin;
int carrier_test = 0;
int one_zero_test = 0;
float frequency = 144.5e6;
int SymbolRate = 10000;
int m = 2;
int log2m;
float shiftHz = -1;
struct freedv *freedv = NULL;
struct freedv_advanced adv;
int fsk_ldpc = 0;
int data_bits_per_frame; // number of payload data bits
int bits_per_frame; // total number of bits including UW, payload data, parity bits for FSK + LDPC mode
int testframes = 0;
int Nframes = 0;
int Nbursts = 1;
int sequence_numbers = 0;
char ant_switch_gpio[128] = "";
char ant_switch_gpio_path[MAX_CHAR] = "";
int rpitx_fsk_fifo = 0;
int packed = 0;
uint8_t source_byte = 0;
int inter_burst_delay_ms = 0;
char usage[] = "usage: %s [-m fskM 2|4] [-f carrierFreqHz] [-r symbRateHz] [-s shiftHz] [-t] [-c] "
"[--testframes Nframes] InputOneBitPerCharFile\n"
" -c Carrier test mode\n"
" -g GPIO that controls antenna Tx/Rx switch (1 for Tx, 0 for Rx)\n"
" -t ...0101010... FSK test mode\n"
" --code CodeName Use LDPC code CodeName\n"
" --listcodes List available LDPC codes\n"
" --testframes N Send N testframes per burst\n"
" --bursts B Send B bursts of N testframes (default 1)\n"
" --delay ms testframe inter-burst delay in ms (default 2 frames)\n"
" --seq send packet sequence numbers (breaks testframe BER counting) in byte[1]\n"
" --fifo fifoName send stats messages to fifoName\n"
" --packed packed byte input\n"
" --source Byte insert a (non-zero) source address att byte[0]\n"
"\n"
" Example 1, send 10000 bits of (100 bit) tests frames from external test frame generator\n"
" at 1000 bits/s using 2FSK:\n\n"
" $ ../codec2/build_linux/src/fsk_get_test_bits - 10000 | sudo ./rpitx_fsk - -r 1000 -s 1000\n\n"
" Example 2, send two LDPC encoded test frames at 1000 bits/s using 2FSK:\n\n"
" $ sudo ./rpitx_fsk /dev/zero --code H_256_512_4 -r 1000 -s 1000 --testframes 2\n";
int opt = 0;
int opt_idx = 0;
while( opt != -1 ){
static struct option long_opts[] = {
{"code", required_argument, 0, 'a'},
{"listcodes", no_argument, 0, 'b'},
{"testframes",required_argument, 0, 'u'},
{"bursts", required_argument, 0, 'e'},
{"seq", no_argument, 0, 'q'},
{"fifo", required_argument, 0, 'i'},
{"packed", no_argument, 0, 'l'},
{"source", required_argument, 0, 'd'},
{"delay", required_argument, 0, 'j'},
{0, 0, 0, 0}
};
opt = getopt_long(argc,argv,"a:bcd:e:f:g:i:m:qr:s:tu:",long_opts,&opt_idx);
switch (opt) {
case 'a':
fsk_ldpc = 1;
adv.codename = optarg;
break;
case 'b':
ldpc_codes_list();
exit(0);
break;
case 'c':
carrier_test = 1;
break;
case 'd':
source_byte = strtol(optarg, NULL, 0);
fprintf(stderr,"source byte: 0x%02x\n", source_byte);
break;
case 'e':
Nbursts = atoi(optarg);
break;
case 'm':
m = atoi(optarg);
break;
case 'l':
packed = 1;
break;
case 'f':
frequency = atof(optarg);
break;
case 'i':
rpitx_fsk_fifo = open(optarg, O_WRONLY);
if (rpitx_fsk_fifo == -1) {
fprintf(stderr, "Error opening fifo %s\n", argv[2]);
exit(1);
}
fprintf(stderr, "rpitx_fsk: FIFO opened OK ...\n");
break;
case 'q':
sequence_numbers = 1;
break;
case 'r':
SymbolRate = atof(optarg);
break;
case 's':
shiftHz = atof(optarg);
break;
case 't':
one_zero_test = 1;
break;
case 'u':
if (fsk_ldpc == 0) {
fprintf(stderr, "internal testframe mode only supported in --code coded mode!\n");
exit(1);
}
testframes = 1;
Nframes = atoi(optarg);
fprintf(stderr, "rpitx_fsk: Sending %d testframe(s)...\n", Nframes);
break;
case 'g':
strcpy(ant_switch_gpio, optarg);
sys_gpio("/sys/class/gpio/unexport", ant_switch_gpio);
sys_gpio("/sys/class/gpio/export", ant_switch_gpio);
usleep(100*1000); /* short delay so OS can create the next device */
char tmp[MAX_CHAR];
sprintf(tmp,"/sys/class/gpio/gpio%s/direction", ant_switch_gpio);
sys_gpio(tmp, "out");
sprintf(ant_switch_gpio_path,"/sys/class/gpio/gpio%s/value", ant_switch_gpio);
sys_gpio(ant_switch_gpio_path, "0");
break;
case 'j':
inter_burst_delay_ms = atoi(optarg);
break;
case 'h':
case '?':
fprintf(stderr, usage, argv[0]);
exit(1);
}
}
if (argc < 2) {
fprintf(stderr, usage, argv[0]);
exit(1);
}
fin = stdin;
if (!(carrier_test || one_zero_test)) {
if (strcmp(argv[optind],"-") != 0) {
fin = fopen(argv[optind],"rb");
if (fin == NULL) {
fprintf(stderr, "Error opening input file: %s\n", argv[optind]);
exit(1);
}
}
}
int npreamble_symbols = 50*(m>>1);
int npreamble_bits = npreamble_symbols*(m>>1);
uint8_t preamble_bits[npreamble_bits];
if (fsk_ldpc) {
// setup LDPC encoder and framer
adv.Rs = SymbolRate;
adv.Fs = 8*SymbolRate; // just required to satisfy freedv_open FSK_LDPC, as we don't run FSK demod here
adv.M = m;
freedv = freedv_open_advanced(FREEDV_MODE_FSK_LDPC, &adv);
assert(freedv != NULL);
data_bits_per_frame = freedv_get_bits_per_modem_frame(freedv);
bits_per_frame = freedv_tx_fsk_ldpc_bits_per_frame(freedv);
fprintf(stderr, "rpitx_fsk: FSK LDPC mode code: %s data_bits_per_frame: %d\n", adv.codename, data_bits_per_frame);
/* set up preamble */
/* TODO: this should be a freeDV API function */
// cycle through all 2 and 4FSK symbols, not sure if this is better than random
int sym = 0;
for(int i=0; i<npreamble_bits; i+=2) {
preamble_bits[i] = (sym>>1) & 0x1;
preamble_bits[i+1] = sym & 0x1;
sym += 1;
}
} else {
// uncoded mode
data_bits_per_frame = log2(m);
bits_per_frame = data_bits_per_frame;
}
/* Start RpiTX ---------------------------------------------------------------------------------*/
// Set shiftHz at 2*Rs if no command line argument
if (shiftHz == -1)
shiftHz = 2*SymbolRate;
dbg_setlevel(1);
fmmod = new ngfmdmasync(frequency,SymbolRate,14,FIFO_SIZE);
initial_frequency = initial_pllc_freq();
fmmod->clkgpio::disableclk(4);
fprintf(stderr, "rpitx_fsk: Frequency: %4.1f MHz Rs: %4.1f kHz Shift: %4.1f kHz M: %d \n", frequency/1E6, SymbolRate/1E3, shiftHz/1E3, m);
fprintf(stderr, "rpitx_fsk: data_bits_per_frame: %d bits_per_frame: %d\n", data_bits_per_frame, bits_per_frame);
if ((carrier_test == 0) && (one_zero_test == 0)) {
// FSK Tx --------------------------------------------------------------------
uint8_t data_bits[data_bits_per_frame];
uint8_t tx_frame[bits_per_frame];
if (testframes) {
/* FSK_LDPC Tx in test frame mode -------------------------------------------*/
assert(fsk_ldpc);
ofdm_generate_payload_data_bits(data_bits, data_bits_per_frame);
for(int b=0; b<Nbursts; b++) {
// antenna switch to Tx
if (*ant_switch_gpio_path) sys_gpio(ant_switch_gpio_path, "1");
// transmitter carrier on
fmmod->clkgpio::enableclk(4);
//fmmod = new ngfmdmasync(frequency,SymbolRate,14,FIFO_SIZE);
// send pre-amble at start of burst
modulate_frame(fmmod, shiftHz, m, preamble_bits, npreamble_bits);
for (int f=0; f<Nframes; f++) {
// optional injection of source address byte
if (source_byte) {
for (int i=0; i<8; i++)
data_bits[i] = (source_byte >> (7-i)) & 0x1;
}
// optional injection of sequence numbers to help locate bad frames
if (sequence_numbers) {
int seq = (f+1) & 0xff;
for (int i=0; i<8; i++)
data_bits[8+i] = (seq >> (7-i)) & 0x1;
}
calculate_and_insert_crc(data_bits, data_bits_per_frame);
freedv_tx_fsk_ldpc_framer(freedv, tx_frame, data_bits);
modulate_frame(fmmod, shiftHz, m, tx_frame, bits_per_frame);
// allow early exit on Crtl-C
if (!running) goto finished;
}
// wait for enough time for FIFO to empty
int bufferSamples = FIFO_SIZE - fmmod->GetBufferAvailable();
float tdelay = (float)bufferSamples/SymbolRate;
usleep((int)(tdelay*1E6));
fprintf(stderr, "rpitx_fsk: End of burst %d\n", b);
// transmitter carrier off between bursts
fmmod->clkgpio::disableclk(4);
//delete fmmod;
// antenna switch to Rx
if (*ant_switch_gpio_path) sys_gpio(ant_switch_gpio_path, "0");
if (inter_burst_delay_ms == 0) {
// Two frames delay so we have some interpacket silence
tdelay = (2.0/SymbolRate)*bits_per_frame/(m>>1);
} else {
tdelay = inter_burst_delay_ms/1E3;
}
usleep((int)(tdelay*1E6));
check_pllc();
}
}
else {
/* regular FSK or FSK_LDPC Tx operation with bits/bytes from stdin ----------------------*/
int nframes = 0;
while(1) {
uint8_t burst_control;
int nRead;
if (fsk_ldpc) {
// in fsk_ldpc mode we prepend input data with a burst control byte
nRead = fread(&burst_control, sizeof(uint8_t), 1, fin);
if (nRead == 0) goto finished;
}
if (packed) {
int data_bytes_per_frame = data_bits_per_frame/8;
uint8_t data_bytes[data_bytes_per_frame];
nRead = fread(data_bytes, sizeof(uint8_t), data_bytes_per_frame, fin);
freedv_unpack(data_bits, data_bytes, data_bits_per_frame);
nRead *= 8;
}
else {
nRead = fread(data_bits, sizeof(uint8_t), data_bits_per_frame, fin);
}
fprintf(stderr, "rpitx_fsk: burst_control: %d nRead: %d\n", burst_control, nRead);
if (nRead != data_bits_per_frame) goto finished;
if (fsk_ldpc) {
// start of burst
if (burst_control == 1) {
fprintf(stderr, "rpitx_fsk: Tx on\n");
// antenna switch to Tx
if (*ant_switch_gpio_path) sys_gpio(ant_switch_gpio_path, "1");
// transmitter carrier on
fmmod->clkgpio::enableclk(4);
//fmmod = new ngfmdmasync(frequency,SymbolRate,14,FIFO_SIZE);
// send preamble
fprintf(stderr, "rpitx_fsk: sending preamble\n");
modulate_frame(fmmod, shiftHz, m, preamble_bits, npreamble_bits);
nframes = 0;
}
if ((burst_control == 0) || (burst_control == 1)) {
fprintf(stderr, "rpitx_fsk: sending frame: %d\n", nframes); nframes++;
// send a data frame, note last two bytes in frame replaced with CRC
calculate_and_insert_crc(data_bits, data_bits_per_frame);
freedv_tx_fsk_ldpc_framer(freedv, tx_frame, data_bits);
modulate_frame(fmmod, shiftHz, m, tx_frame, bits_per_frame);
}
// end of burst - this has a dummy data frame so don't send
if (burst_control == 2) {
// wait for enough time for FIFO to empty
int bufferSamples = FIFO_SIZE - fmmod->GetBufferAvailable();
float tdelay = (float)bufferSamples/SymbolRate;
usleep((int)(tdelay*1E6));
// transmitter carrier off between bursts
fmmod->clkgpio::disableclk(4);
//delete fmmod;
// antenna switch to Rx
if (*ant_switch_gpio_path) sys_gpio(ant_switch_gpio_path, "0");
fprintf(stderr, "rpitx_fsk: Tx off\n");
if (rpitx_fsk_fifo) {
char buf[256];
sprintf(buf, "Tx off");
if (write(rpitx_fsk_fifo, buf, strlen(buf)+1) ==-1) {
fprintf(stderr, "rpitx_fsk: error writing to FIFO\n");
}
}
}
}
else {
// uncoded mode - just send data_bits without any further framing
memcpy(tx_frame, data_bits, data_bits_per_frame);
modulate_frame(fmmod, shiftHz, m, tx_frame, bits_per_frame);
}
// allow us to bail on Ctrl-C
if (!running) goto finished;
check_pllc();
}
}
}
if (carrier_test) {
fprintf(stderr, "Carrier test mode 1 sec on/off , Ctrl-C to exit\n");
int count = 0;
int cycles = 0;
float VCOfreqHz = 0;
fmmod->clkgpio::enableclk(4);
while(running) {
//fmmod->SetFrequencySamples(&VCOfreqHz,1);
while (SetFrequencySampleNonBlocking(fmmod, VCOfreqHz)) usleep(100);
count++;
if (count == SymbolRate)
fmmod->clkgpio::disableclk(4);
if (count == 2*SymbolRate) {
fmmod->clkgpio::enableclk(4);
count = 0;
fprintf(stderr,"\rcycles: %d", ++cycles);
}
}
}
if (one_zero_test) {
fprintf(stderr, "...010101... test mode, Ctrl-C to exit\n");
float VCOfreqHz = 0;
fmmod->clkgpio::enableclk(4);
while(running) {
if (VCOfreqHz == shiftHz)
VCOfreqHz = 0;
else
VCOfreqHz = shiftHz;
while (SetFrequencySampleNonBlocking(fmmod, VCOfreqHz)) usleep(100);
}
}
finished:
check_pllc();
fprintf(stderr, "finishing....\n");
if (fmmod) delete fmmod;
if (fsk_ldpc) freedv_close(freedv);
if (*ant_switch_gpio) {
sys_gpio(ant_switch_gpio_path, "0");
sys_gpio("/sys/class/gpio/unexport", ant_switch_gpio);
}
return 0;
}