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tests/driver_dac_dds: make use of imath

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Benjamin Valentin 2023-03-10 13:27:50 +01:00 committed by Benjamin Valentin
parent c23cec9776
commit 69a6b3cb14
1 changed files with 5 additions and 36 deletions
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41
tests/drivers/dac_dds/main.c
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@ -31,6 +31,7 @@
#include "mutex.h" #include "mutex.h"
#include "dac_dds.h" #include "dac_dds.h"
#include "dac_dds_params.h" #include "dac_dds_params.h"
#include "imath.h"
#include "shell.h" #include "shell.h"
#include "blob/hello.raw.h" #include "blob/hello.raw.h"
@ -58,38 +59,6 @@
static bool res_16b = 0; static bool res_16b = 0;
static unsigned sample_rate = 8000; static unsigned sample_rate = 8000;
#define ISIN_PERIOD (0x7FFF)
#define ISIN_MAX (0x1000)
/**
* @brief A sine approximation via a fourth-order cosine approx.
* source: https://www.coranac.com/2009/07/sines/
*
* @param x angle (with 2^15 units/circle)
* @return sine value (Q12)
*/
static int32_t isin(int32_t x)
{
int32_t c, y;
static const int32_t qN = 13,
qA = 12,
B = 19900,
C = 3516;
c = x << (30 - qN); /* Semi-circle info into carry. */
x -= 1 << qN; /* sine -> cosine calc */
x = x << (31 - qN); /* Mask with PI */
x = x >> (31 - qN); /* Note: SIGNED shift! (to qN) */
x = x * x >> (2 * qN - 14); /* x=x^2 To Q14 */
y = B - (x * C >> 14); /* B - x^2*C */
y = (1 << qA) /* A - x^2*(B-x^2*C) */
- (x * y >> 16);
return c >= 0 ? y : -y;
}
/* simple function to fill buffer with samples /* simple function to fill buffer with samples
* *
* It is up to the caller to ensure that len is always at least period. * It is up to the caller to ensure that len is always at least period.
@ -115,11 +84,11 @@ static void _fill_saw_samples_16(uint8_t *buf, size_t len, uint16_t period)
static void _fill_sine_samples_8(uint8_t *buf, size_t len, uint16_t period) static void _fill_sine_samples_8(uint8_t *buf, size_t len, uint16_t period)
{ {
uint16_t x = 0; uint16_t x = 0;
unsigned step = ISIN_PERIOD / period; unsigned step = SINI_PERIOD / period;
for (uint16_t i = 0; i < period; ++i) { for (uint16_t i = 0; i < period; ++i) {
x += step; x += step;
buf[i] = (isin(x) + 4096) >> 6; buf[i] = (fast_sini(x) - SINI_MIN) >> 6;
} }
for (uint16_t i = period; i < len; i += period) { for (uint16_t i = period; i < len; i += period) {
@ -130,14 +99,14 @@ static void _fill_sine_samples_8(uint8_t *buf, size_t len, uint16_t period)
static void _fill_sine_samples_16(uint8_t *buf, size_t len, uint16_t period) static void _fill_sine_samples_16(uint8_t *buf, size_t len, uint16_t period)
{ {
uint16_t x = 0; uint16_t x = 0;
unsigned step = ISIN_PERIOD / period; unsigned step = SINI_PERIOD / period;
period *= 2; period *= 2;
for (uint16_t i = 0; i < period; ++i) { for (uint16_t i = 0; i < period; ++i) {
x += step; x += step;
uint16_t y = (isin(x) + 4096) << 2; uint16_t y = (fast_sini(x) - SINI_MIN) << 2;
buf[i] = y; buf[i] = y;
buf[++i] = y >> 8; buf[++i] = y >> 8;
} }