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Code Issues Releases Activity

Represent frequency and deviation in PyFmDma as #defines instead of magic numbers

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This commit is contained in:
Dan Ankers 2012-12-18 11:52:50 +00:00
parent 6f2ff5fb6f
commit 1cee99150d
1 changed files with 14 additions and 4 deletions
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18
PiFmDma/PiFmDma.c
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@ -138,6 +138,12 @@
#define GPFSEL0 (0x00/4) #define GPFSEL0 (0x00/4)
#define PLLFREQ 500000000 // PLLD is running at 500MHz
#define CARRIERFREQ 100000000 // Carrier frequency is 100MHz
// 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 { typedef struct {
uint32_t info, src, dst, length, uint32_t info, src, dst, length,
stride, next, pad[2]; stride, next, pad[2];
@ -241,7 +247,7 @@ map_peripheral(uint32_t base, uint32_t len)
int int
main(int argc, char **argv) main(int argc, char **argv)
{ {
int i, fd, pid; int i, fd, pid, freq_ctl;
char pagemap_fn[64]; char pagemap_fn[64];
// Catch all signals possible - it is vital we kill the DMA engine // Catch all signals possible - it is vital we kill the DMA engine
@ -253,6 +259,10 @@ main(int argc, char **argv)
sa.sa_handler = terminate; sa.sa_handler = terminate;
sigaction(i, &sa, NULL); sigaction(i, &sa, NULL);
} }
// Calculate the frequency control word
// The fractional part is stored in the lower 12 bits
freq_ctl = ((float)(PLLFREQ / CARRIERFREQ)) * ( 1 << 12 );
dma_reg = map_peripheral(DMA_BASE, DMA_LEN); dma_reg = map_peripheral(DMA_BASE, DMA_LEN);
pwm_reg = map_peripheral(PWM_BASE, PWM_LEN); pwm_reg = map_peripheral(PWM_BASE, PWM_LEN);
@ -305,7 +315,7 @@ main(int argc, char **argv)
uint32_t phys_pwm_fifo_addr = 0x7e20c000 + 0x18; uint32_t phys_pwm_fifo_addr = 0x7e20c000 + 0x18;
for (i = 0; i < NUM_SAMPLES; i++) { for (i = 0; i < NUM_SAMPLES; i++) {
ctl->sample[i] = 0x5a << 24 | 5 << 12; // Silence ctl->sample[i] = 0x5a << 24 | freq_ctl; // Silence
// Write a frequency sample // Write a frequency sample
cbp->info = BCM2708_DMA_NO_WIDE_BURSTS | BCM2708_DMA_WAIT_RESP; cbp->info = BCM2708_DMA_NO_WIDE_BURSTS | BCM2708_DMA_WAIT_RESP;
cbp->src = mem_virt_to_phys(ctl->sample + i); cbp->src = mem_virt_to_phys(ctl->sample + i);
@ -387,7 +397,7 @@ main(int argc, char **argv)
free_slots += NUM_SAMPLES; free_slots += NUM_SAMPLES;
while (free_slots >= 10) { while (free_slots >= 10) {
float dval = (float)(data[data_index])/65536.0 * 25.0; float dval = (float)(data[data_index])/65536.0 * DEVIATION;
int intval = (int)((floor)(dval)); int intval = (int)((floor)(dval));
int frac = (int)((dval - (float)intval) * 10.0); int frac = (int)((dval - (float)intval) * 10.0);
int j; int j;
@ -396,7 +406,7 @@ main(int argc, char **argv)
// distributing the '+1's evenly across the 10 subsamples, or maybe // distributing the '+1's evenly across the 10 subsamples, or maybe
// by taking the previous and next samples in to account too. // by taking the previous and next samples in to account too.
for (j = 0; j < 10; j++) { for (j = 0; j < 10; j++) {
ctl->sample[last_sample++] = (0x5A << 24 | 5 << 12) + (frac > j ? intval + 1 : intval); ctl->sample[last_sample++] = (0x5A << 24 | freq_ctl) + (frac > j ? intval + 1 : intval);
if (last_sample == NUM_SAMPLES) if (last_sample == NUM_SAMPLES)
last_sample = 0; last_sample = 0;
} }