tests/driver_dac_dds: fix output of sine and saw functions

benpicco · benpicco · commit 65fccdd55a04 · 2023-02-06T14:18:37.000+01:00
diff --git a/tests/driver_dac_dds/main.c b/tests/driver_dac_dds/main.c
@@ -98,24 +98,17 @@ typedef void (*sample_gen_t)(uint8_t *dst, size_t len, uint16_t period);
 
 static void _fill_saw_samples_8(uint8_t *buf, size_t len, uint16_t period)
 {
-    uint8_t x = 0;
-    unsigned step = 0xFF / period;
-
     for (uint16_t i = 0; i < len; ++i) {
-        x += step;
-        buf[i] = x;
+        buf[i] = (i * 0xFFUL) / period;
     }
 }
 
 static void _fill_saw_samples_16(uint8_t *buf, size_t len, uint16_t period)
 {
-    uint16_t x = 0;
-    unsigned step = 0xFFFF / period;
-
     for (uint16_t i = 0; i < len; ++i) {
-        x += step;
-        buf[i]   = x;
-        buf[++i] = x >> 8;
+        uint16_t y = (i * 0xFFFFUL) / period;
+        buf[i]   = y;
+        buf[++i] = y >> 8;
     }
 }
 
@@ -126,8 +119,7 @@ static void _fill_sine_samples_8(uint8_t *buf, size_t len, uint16_t period)
 
     for (uint16_t i = 0; i < period; ++i) {
         x += step;
-        buf[i] = isin(x) >> 5;
-        buf[i] += INT8_MAX + 1;
+        buf[i] = (isin(x) + 4096) >> 6;
     }
 
     for (uint16_t i = period; i < len; i += period) {
@@ -145,8 +137,7 @@ static void _fill_sine_samples_16(uint8_t *buf, size_t len, uint16_t period)
     for (uint16_t i = 0; i < period; ++i) {
         x += step;
 
-        uint16_t y = isin(x);
-        y += INT16_MAX + 1;
+        uint16_t y = (isin(x) + 4096) << 2;
         buf[i]   = y;
         buf[++i] = y >> 8;
     }

Original file line number	Diff line number	Diff line change
`@@ -98,24 +98,17 @@ typedef void (sample_gen_t)(uint8_t dst, size_t len, uint16_t period);`
`98`	`98`
`99`	`99`	`static void _fill_saw_samples_8(uint8_t *buf, size_t len, uint16_t period)`
`100`	`100`	`{`
`101`		`- uint8_t x = 0;`
`102`		`- unsigned step = 0xFF / period;`
`103`		`-`
`104`	`101`	`for (uint16_t i = 0; i < len; ++i) {`
`105`		`- x += step;`
`106`		`- buf[i] = x;`
	`102`	`+ buf[i] = (i * 0xFFUL) / period;`
`107`	`103`	`}`
`108`	`104`	`}`
`109`	`105`
`110`	`106`	`static void _fill_saw_samples_16(uint8_t *buf, size_t len, uint16_t period)`
`111`	`107`	`{`
`112`		`- uint16_t x = 0;`
`113`		`- unsigned step = 0xFFFF / period;`
`114`		`-`
`115`	`108`	`for (uint16_t i = 0; i < len; ++i) {`
`116`		`- x += step;`
`117`		`- buf[i] = x;`
`118`		`- buf[++i] = x >> 8;`
	`109`	`+ uint16_t y = (i * 0xFFFFUL) / period;`
	`110`	`+ buf[i] = y;`
	`111`	`+ buf[++i] = y >> 8;`
`119`	`112`	`}`
`120`	`113`	`}`
`121`	`114`
`@@ -126,8 +119,7 @@ static void _fill_sine_samples_8(uint8_t *buf, size_t len, uint16_t period)`
`126`	`119`
`127`	`120`	`for (uint16_t i = 0; i < period; ++i) {`
`128`	`121`	`x += step;`
`129`		`- buf[i] = isin(x) >> 5;`
`130`		`- buf[i] += INT8_MAX + 1;`
	`122`	`+ buf[i] = (isin(x) + 4096) >> 6;`
`131`	`123`	`}`
`132`	`124`
`133`	`125`	`for (uint16_t i = period; i < len; i += period) {`
`@@ -145,8 +137,7 @@ static void _fill_sine_samples_16(uint8_t *buf, size_t len, uint16_t period)`
`145`	`137`	`for (uint16_t i = 0; i < period; ++i) {`
`146`	`138`	`x += step;`
`147`	`139`
`148`		`- uint16_t y = isin(x);`
`149`		`- y += INT16_MAX + 1;`
	`140`	`+ uint16_t y = (isin(x) + 4096) << 2;`
`150`	`141`	`buf[i] = y;`
`151`	`142`	`buf[++i] = y >> 8;`
`152`	`143`	`}`