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F5OEO-PiFmRds
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F5OEO-PiFmRds/src/pi_fm_rds.c

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/*
* PiFmRds - FM/RDS transmitter for the Raspberry Pi
* Copyright (C) 2014 Christophe Jacquet, F8FTK
* Copyright (C) 2012 Richard Hirst
* Copyright (C) 2012 Oliver Mattos and Oskar Weigl
*
* See https://github.com/ChristopheJacquet/PiFmRds
*
* PI-FM-RDS: RaspberryPi FM transmitter, with RDS.
*
* This file contains the VHF FM modulator. All credit goes to the original
* authors, Oliver Mattos and Oskar Weigl for the original idea, and to
* Richard Hirst for using the Pi's DMA engine, which reduced CPU usage
* dramatically.
*
* I (Christophe Jacquet) have adapted their idea to transmitting samples
* at 228 kHz, allowing to build the 57 kHz subcarrier for RDS BPSK data.
*
* Never use this to transmit VHF-FM data through an antenna, as it is
* illegal in most countries. This code is for testing purposes only.
* Always connect a shielded transmission line from the RaspberryPi directly
* to a radio receiver, so as *not* to emit radio waves.
*
* ---------------------------------------------------------------------------
* These are the comments from Richard Hirst's version:
*
* RaspberryPi based FM transmitter. For the original idea, see:
*
* http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter
*
* All credit to Oliver Mattos and Oskar Weigl for creating the original code.
*
* I have taken their idea and reworked it to use the Pi DMA engine, so
* reducing the CPU overhead for playing a .wav file from 100% to about 1.6%.
*
* I have implemented this in user space, using an idea I picked up from Joan
* on the Raspberry Pi forums - credit to Joan for the DMA from user space
* idea.
*
* The idea of feeding the PWM FIFO in order to pace DMA control blocks comes
* from ServoBlaster, and I take credit for that :-)
*
* This code uses DMA channel 0 and the PWM hardware, with no regard for
* whether something else might be trying to use it at the same time (such as
* the 3.5mm jack audio driver).
*
* I know nothing much about sound, subsampling, or FM broadcasting, so it is
* quite likely the sound quality produced by this code can be improved by
* someone who knows what they are doing. There may be issues realting to
* caching, as the user space process just writes to its virtual address space,
* and expects the DMA controller to see the data; it seems to work for me
* though.
*
* NOTE: THIS CODE MAY WELL CRASH YOUR PI, TRASH YOUR FILE SYSTEMS, AND
* POTENTIALLY EVEN DAMAGE YOUR HARDWARE. THIS IS BECAUSE IT STARTS UP THE DMA
* CONTROLLER USING MEMORY OWNED BY A USER PROCESS. IF THAT USER PROCESS EXITS
* WITHOUT STOPPING THE DMA CONTROLLER, ALL HELL COULD BREAK LOOSE AS THE
* MEMORY GETS REALLOCATED TO OTHER PROCESSES WHILE THE DMA CONTROLLER IS STILL
* USING IT. I HAVE ATTEMPTED TO MINIMISE ANY RISK BY CATCHING SIGNALS AND
* RESETTING THE DMA CONTROLLER BEFORE EXITING, BUT YOU HAVE BEEN WARNED. I
* ACCEPT NO LIABILITY OR RESPONSIBILITY FOR ANYTHING THAT HAPPENS AS A RESULT
* OF YOU RUNNING THIS CODE. IF IT BREAKS, YOU GET TO KEEP ALL THE PIECES.
*
* NOTE ALSO: THIS MAY BE ILLEGAL IN YOUR COUNTRY. HERE ARE SOME COMMENTS
* FROM MORE KNOWLEDGEABLE PEOPLE ON THE FORUM:
*
* "Just be aware that in some countries FM broadcast and especially long
* distance FM broadcast could get yourself into trouble with the law, stray FM
* broadcasts over Airband aviation is also strictly forbidden."
*
* "A low pass filter is really really required for this as it has strong
* harmonics at the 3rd, 5th 7th and 9th which sit in licensed and rather
* essential bands, ie GSM, HAM, emergency services and others. Polluting these
* frequencies is immoral and dangerous, whereas "breaking in" on FM bands is
* just plain illegal."
*
* "Don't get caught, this GPIO use has the potential to exceed the legal
* limits by about 2000% with a proper aerial."
*
*
* As for the original code, this code is released under the GPL.
*
* Richard Hirst <richardghirst@gmail.com> December 2012
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <stdarg.h>
#include <stdint.h>
#include <math.h>
#include <time.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sndfile.h>
#include "rds.h"
#include "fm_mpx.h"
#define NUM_SAMPLES 50000
#define NUM_CBS (NUM_SAMPLES * 2)
#define BCM2708_DMA_NO_WIDE_BURSTS (1<<26)
#define BCM2708_DMA_WAIT_RESP (1<<3)
#define BCM2708_DMA_D_DREQ (1<<6)
#define BCM2708_DMA_PER_MAP(x) ((x)<<16)
#define BCM2708_DMA_END (1<<1)
#define BCM2708_DMA_RESET (1<<31)
#define BCM2708_DMA_INT (1<<2)
#define DMA_CS (0x00/4)
#define DMA_CONBLK_AD (0x04/4)
#define DMA_DEBUG (0x20/4)
#define DMA_BASE 0x20007000
#define DMA_LEN 0x24
#define PWM_BASE 0x2020C000
#define PWM_LEN 0x28
#define CLK_BASE 0x20101000
#define CLK_LEN 0xA8
#define GPIO_BASE 0x20200000
#define GPIO_LEN 0xB4
#define PWM_CTL (0x00/4)
#define PWM_DMAC (0x08/4)
#define PWM_RNG1 (0x10/4)
#define PWM_FIFO (0x18/4)
#define PWMCLK_CNTL 40
#define PWMCLK_DIV 41
#define GPCLK_CNTL (0x70/4)
#define GPCLK_DIV (0x74/4)
#define PWMCTL_MODE1 (1<<1)
#define PWMCTL_PWEN1 (1<<0)
#define PWMCTL_CLRF (1<<6)
#define PWMCTL_USEF1 (1<<5)
#define PWMDMAC_ENAB (1<<31)
// I think this means it requests as soon as there is one free slot in the FIFO
// which is what we want as burst DMA would mess up our timing..
#define PWMDMAC_THRSHLD ((15<<8)|(15<<0))
#define GPFSEL0 (0x00/4)
#define PLLFREQ 500000000. // PLLD is running at 500MHz ////
// The deviation specifies how wide the signal is. Use 25.0 for WBFM
// (broadcast radio) and about 3.5 for NBFM (walkie-talkie style radio)
#define DEVIATION 25.0
typedef struct {
uint32_t info, src, dst, length,
stride, next, pad[2];
} dma_cb_t;
typedef struct {
uint8_t *virtaddr;
uint32_t physaddr;
} page_map_t;
page_map_t *page_map;
static uint8_t *virtbase;
static volatile uint32_t *pwm_reg;
static volatile uint32_t *clk_reg;
static volatile uint32_t *dma_reg;
static volatile uint32_t *gpio_reg;
struct control_data_s {
dma_cb_t cb[NUM_CBS];
uint32_t sample[NUM_SAMPLES];
};
#define PAGE_SIZE 4096
#define PAGE_SHIFT 12
#define NUM_PAGES ((sizeof(struct control_data_s) + PAGE_SIZE - 1) >> PAGE_SHIFT)
static struct control_data_s *ctl;
static void
udelay(int us)
{
struct timespec ts = { 0, us * 1000 };
nanosleep(&ts, NULL);
}
static void
terminate(int dummy)
{
if (dma_reg) {
dma_reg[DMA_CS] = BCM2708_DMA_RESET;
udelay(10);
}
fm_mpx_close();
exit(1);
}
static void
fatal(char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vfprintf(stderr, fmt, ap);
va_end(ap);
terminate(0);
}
static uint32_t
mem_virt_to_phys(void *virt)
{
uint32_t offset = (uint8_t *)virt - virtbase;
return page_map[offset >> PAGE_SHIFT].physaddr + (offset % PAGE_SIZE);
}
static uint32_t
mem_phys_to_virt(uint32_t phys)
{
uint32_t pg_offset = phys & (PAGE_SIZE - 1);
uint32_t pg_addr = phys - pg_offset;
int i;
for (i = 0; i < NUM_PAGES; i++) {
if (page_map[i].physaddr == pg_addr) {
return (uint32_t)virtbase + i * PAGE_SIZE + pg_offset;
}
}
fatal("Failed to reverse map phys addr %08x\n", phys);
return 0;
}
static void *
map_peripheral(uint32_t base, uint32_t len)
{
int fd = open("/dev/mem", O_RDWR);
void * vaddr;
if (fd < 0)
fatal("Failed to open /dev/mem: %m\n");
vaddr = mmap(NULL, len, PROT_READ|PROT_WRITE, MAP_SHARED, fd, base);
if (vaddr == MAP_FAILED)
fatal("Failed to map peripheral at 0x%08x: %m\n", base);
close(fd);
return vaddr;
}
#define SUBSIZE 1
#define DATA_SIZE 5000
int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt, int16_t ppm) {
int i, fd, pid;
char pagemap_fn[64];
// Catch all signals possible - it is vital we kill the DMA engine
// on process exit!
for (i = 0; i < 64; i++) {
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = terminate;
sigaction(i, &sa, NULL);
}
dma_reg = map_peripheral(DMA_BASE, DMA_LEN);
pwm_reg = map_peripheral(PWM_BASE, PWM_LEN);
clk_reg = map_peripheral(CLK_BASE, CLK_LEN);
gpio_reg = map_peripheral(GPIO_BASE, GPIO_LEN);
virtbase = mmap(NULL, NUM_PAGES * PAGE_SIZE, PROT_READ|PROT_WRITE,
MAP_SHARED|MAP_ANONYMOUS|MAP_NORESERVE|MAP_LOCKED,
-1, 0);
if (virtbase == MAP_FAILED)
fatal("Failed to mmap physical pages: %m\n");
if ((unsigned long)virtbase & (PAGE_SIZE-1))
fatal("Virtual address is not page aligned\n");
printf("Virtual memory mapped at %p\n", virtbase);
page_map = malloc(NUM_PAGES * sizeof(*page_map));
if (page_map == 0)
fatal("Failed to malloc page_map: %m\n");
pid = getpid();
sprintf(pagemap_fn, "/proc/%d/pagemap", pid);
fd = open(pagemap_fn, O_RDONLY);
if (fd < 0)
fatal("Failed to open %s: %m\n", pagemap_fn);
if (lseek(fd, (unsigned long)virtbase >> 9, SEEK_SET) != (unsigned long)virtbase >> 9)
fatal("Failed to seek on %s: %m\n", pagemap_fn);
// printf("Page map:\n");
for (i = 0; i < NUM_PAGES; i++) {
uint64_t pfn;
page_map[i].virtaddr = virtbase + i * PAGE_SIZE;
// Following line forces page to be allocated
page_map[i].virtaddr[0] = 0;
if (read(fd, &pfn, sizeof(pfn)) != sizeof(pfn))
fatal("Failed to read %s: %m\n", pagemap_fn);
if (((pfn >> 55)&0xfbf) != 0x10c) // pagemap bits: https://www.kernel.org/doc/Documentation/vm/pagemap.txt
fatal("Page %d not present (pfn 0x%016llx)\n", i, pfn);
page_map[i].physaddr = (uint32_t)pfn << PAGE_SHIFT | 0x40000000;
// printf(" %2d: %8p ==> 0x%08x [0x%016llx]\n", i, page_map[i].virtaddr, page_map[i].physaddr, pfn);
}
// GPIO4 needs to be ALT FUNC 0 to otuput the clock
gpio_reg[GPFSEL0] = (gpio_reg[GPFSEL0] & ~(7 << 12)) | (4 << 12);
// Program GPCLK to use MASH setting 1, so fractional dividers work
clk_reg[GPCLK_CNTL] = 0x5A << 24 | 6;
udelay(100);
clk_reg[GPCLK_CNTL] = 0x5A << 24 | 1 << 9 | 1 << 4 | 6;
ctl = (struct control_data_s *)virtbase;
dma_cb_t *cbp = ctl->cb;
uint32_t phys_sample_dst = 0x7e101074;
uint32_t phys_pwm_fifo_addr = 0x7e20c000 + 0x18;
// Calculate the frequency control word
// The fractional part is stored in the lower 12 bits
uint32_t freq_ctl = ((float)(PLLFREQ / carrier_freq)) * ( 1 << 12 );
for (i = 0; i < NUM_SAMPLES; i++) {
ctl->sample[i] = 0x5a << 24 | freq_ctl; // Silence
// Write a frequency sample
cbp->info = BCM2708_DMA_NO_WIDE_BURSTS | BCM2708_DMA_WAIT_RESP;
cbp->src = mem_virt_to_phys(ctl->sample + i);
cbp->dst = phys_sample_dst;
cbp->length = 4;
cbp->stride = 0;
cbp->next = mem_virt_to_phys(cbp + 1);
cbp++;
// Delay
cbp->info = BCM2708_DMA_NO_WIDE_BURSTS | BCM2708_DMA_WAIT_RESP | BCM2708_DMA_D_DREQ | BCM2708_DMA_PER_MAP(5);
cbp->src = mem_virt_to_phys(virtbase);
cbp->dst = phys_pwm_fifo_addr;
cbp->length = 4;
cbp->stride = 0;
cbp->next = mem_virt_to_phys(cbp + 1);
cbp++;
}
cbp--;
cbp->next = mem_virt_to_phys(virtbase);
// Here we define the rate at which we want to update the GPCLK control
// register.
//
// Set the range to 2 bits. PLLD is at 500 MHz, therefore to get 228 kHz
// we need a divisor of 500000 / 2 / 228 = 1096.491228
//
// This is 1096 + 2012*2^-12 theoretically
//
// However the fractional part may have to be adjusted to take the actual
// frequency of your Pi's oscillator into account. For example on my Pi,
// the fractional part should be 1916 instead of 2012 to get exactly
// 228 kHz. However RDS decoding is still okay even at 2012.
//
// So we use the 'ppm' parameter to compensate for the oscillator error
float divider = (500000./(2*228*(1.+ppm/1.e6)));
uint32_t idivider = (uint32_t) divider;
uint32_t fdivider = (uint32_t) ((divider - idivider)*pow(2, 12));
printf("ppm corr is %d, divider is %.4f (%d + %d*2^-12) [nominal 1096.4912]\n",
ppm, divider, idivider, fdivider);
pwm_reg[PWM_CTL] = 0;
udelay(10);
clk_reg[PWMCLK_CNTL] = 0x5A000006; // Source=PLLD and disable
udelay(100);
// theorically : 1096 + 2012*2^-12
clk_reg[PWMCLK_DIV] = 0x5A000000 | (idivider<<12) | fdivider;
udelay(100);
clk_reg[PWMCLK_CNTL] = 0x5A000216; // Source=PLLD and enable + MASH filter 1
udelay(100);
pwm_reg[PWM_RNG1] = 2;
udelay(10);
pwm_reg[PWM_DMAC] = PWMDMAC_ENAB | PWMDMAC_THRSHLD;
udelay(10);
pwm_reg[PWM_CTL] = PWMCTL_CLRF;
udelay(10);
pwm_reg[PWM_CTL] = PWMCTL_USEF1 | PWMCTL_PWEN1;
udelay(10);
// Initialise the DMA
dma_reg[DMA_CS] = BCM2708_DMA_RESET;
udelay(10);
dma_reg[DMA_CS] = BCM2708_DMA_INT | BCM2708_DMA_END;
dma_reg[DMA_CONBLK_AD] = mem_virt_to_phys(ctl->cb);
dma_reg[DMA_DEBUG] = 7; // clear debug error flags
dma_reg[DMA_CS] = 0x10880001; // go, mid priority, wait for outstanding writes
uint32_t last_cb = (uint32_t)ctl->cb;
// Data structures for baseband data
float data[DATA_SIZE];
int data_len = 0;
int data_index = 0;
// Initialize the baseband generator
if(fm_mpx_open(audio_file, DATA_SIZE) < 0) return -1;
// Initialize the RDS modulator
char myps[9] = {0};
set_rds_pi(pi);
set_rds_rt(rt);
uint16_t count = 0;
uint16_t count2 = 0;
if(ps) {
set_rds_ps(ps);
printf("PI: %04X, PS: \"%s\"\n", pi, ps);
} else {
printf("PI: %04X, PS: <Varying>\n", pi);
}
printf("RT: \"%s\"\n", rt);
printf("Starting to transmit on %3.1f MHz.\n", carrier_freq/1e6);
for (;;) {
// Default (varying) PS
if(!ps) {
if(count == 512) {
snprintf(myps, 9, "%08d", count2);
set_rds_ps(myps);
count2++;
}
if(count == 1024) {
set_rds_ps("RPi-Live");
count = 0;
}
count++;
}
usleep(5000);
uint32_t cur_cb = mem_phys_to_virt(dma_reg[DMA_CONBLK_AD]);
int last_sample = (last_cb - (uint32_t)virtbase) / (sizeof(dma_cb_t) * 2);
int this_sample = (cur_cb - (uint32_t)virtbase) / (sizeof(dma_cb_t) * 2);
int free_slots = this_sample - last_sample;
if (free_slots < 0)
free_slots += NUM_SAMPLES;
while (free_slots >= SUBSIZE) {
// get more baseband samples if necessary
if(data_len == 0) {
fm_mpx_get_samples(data);
data_len = DATA_SIZE;
data_index = 0;
}
float dval = data[data_index] * (DEVIATION / 10.);
data_index++;
data_len--;
int intval = (int)((floor)(dval));
//int frac = (int)((dval - (float)intval) * SUBSIZE);
ctl->sample[last_sample++] = (0x5A << 24 | freq_ctl) + intval; //(frac > j ? intval + 1 : intval);
if (last_sample == NUM_SAMPLES)
last_sample = 0;
free_slots -= SUBSIZE;
}
last_cb = (uint32_t)virtbase + last_sample * sizeof(dma_cb_t) * 2;
}
terminate(0);
return 0;
}
int main(int argc, char **argv) {
char *audio_file = NULL;
uint32_t carrier_freq = 107900000;
char *ps = NULL;
char *rt = "PiFmRds: live FM-RDS transmission from the RaspberryPi";
uint16_t pi = 0x1234;
int16_t ppm = 0;
for(int i=1; i<argc; i++) {
char *arg = argv[i];
char *param = NULL;
if(arg[0] == '-' && i+1 < argc) param = argv[i+1];
if((strcmp("-wav", arg)==0 || strcmp("-audio", arg)==0) && param != NULL) {
i++;
audio_file = param;
} else if(strcmp("-freq", arg)==0 && param != NULL) {
i++;
carrier_freq = 1e6 * atof(param);
if(carrier_freq < 87500000 || carrier_freq > 108000000)
fatal("Incorrect frequency specification. Must be in megahertz, of the form 107.9\n");
} else if(strcmp("-pi", arg)==0 && param != NULL) {
i++;
pi = (uint16_t) strtol(param, NULL, 16);
} else if(strcmp("-ps", arg)==0 && param != NULL) {
i++;
ps = param;
} else if(strcmp("-rt", arg)==0 && param != NULL) {
i++;
rt = param;
} else if(strcmp("-ppm", arg)==0 && param != NULL) {
i++;
ppm = atoi(param);
} else {
fatal("Unrecognised argument: %s\n"
"Syntax: pi_fm_rds [-freq freq] [-audio file] [-ppm ppm_error] [-pi pi_code] [-ps ps_text] [-rt rt_text]\n", arg);
}
}
tx(carrier_freq, audio_file, pi, ps, rt, ppm);
}
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