~jeffpc/fox commit - sourcehut hg

08a6a7fc77ca — Josef 'Jeff' Sipek tip 2 years ago

tones: keep frequencies in tone tables in 8.8 fixed point format

The phase calculation is already done using fixed point math, so we can
trivially feed it tone frequencies in the same format.  This results in the
tones being closer to the desired frequencies.  E.g., a E6 will sound as
1319 Hz (as it should) instead of 1344 Hz as before.

Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>

patch browse

3 files changed, 10 insertions(+), 10 deletions(-)

M fmfox.h
M main.c
M tones.c

M fmfox.h +3 -3

@@ 47,8 47,8 @@ 
  * Various tone sequences
  */
 extern const __flash uint8_t sine_wave[WAVE_STEPS / 4 + 1];
-extern const __flash uint8_t tones_fixed[10];
-extern const __flash uint8_t tones_lfsr[16];
-extern const __flash uint8_t tones_morse[2];
+extern const __flash uint16_t tones_fixed[10];
+extern const __flash uint16_t tones_lfsr[16];
+extern const __flash uint16_t tones_morse[2];
 
 #endif

M main.c +3 -3

@@ 378,7 378,7 @@ void gen_sample(void)
 				tone = next_fixed_tone(tone);
 			}
 
-			dphase = tones_fixed[tone] << 8;
+			dphase = tones_fixed[tone];
 			break;
 		case STATE_PLAYING_LFSR:
 			if (!steps) {

          
@@ 386,7 386,7 @@ void gen_sample(void)
 				tone = next_lfsr_tone(tone);
 			}
 
-			dphase = tones_lfsr[tone] << 8;
+			dphase = tones_lfsr[tone];
 			break;
 		case STATE_PLAYING_IDENT:
 			if (!steps) {

          
@@ 401,7 401,7 @@ void gen_sample(void)
 					phase = 0;
 			}
 
-			dphase = tones_morse[tone] << 8;
+			dphase = tones_morse[tone];
 			break;
 	}

M tones.c +4 -4

@@ 25,7 25,7 @@ 
 
 #define DIV_ROUND_UP(x, y)	(((x) + (y) - 1) / (y))
 #define HZ_TO_STEPS(freq) \
-	DIV_ROUND_UP((freq), (OUT_SAMPLE_RATE / WAVE_STEPS))
+	DIV_ROUND_UP((freq) * 256ul, (OUT_SAMPLE_RATE / WAVE_STEPS))
 
 #define E4	HZ_TO_STEPS(330)
 #define G4	HZ_TO_STEPS(392)

          
@@ 44,12 44,12 @@ 
 #define D7	HZ_TO_STEPS(2349)
 
 /* a fixed sequence of tones that play in order */
-const __flash uint8_t tones_fixed[] = {
+const __flash uint16_t tones_fixed[] = {
 	C6, C5, D6, D5, E6, E5, G6, G5, A6, A5,
 };
 
 /* a set of tones for a 4-bit LFSR */
-const __flash uint8_t tones_lfsr[16] = {
+const __flash uint16_t tones_lfsr[16] = {
 	0, /* never used since LFSRs are never 0 */
 	E4, G4, A4,
 	C5, D5, E5, G5, A5,

          
@@ 57,6 57,6 @@ const __flash uint8_t tones_lfsr[16] = {
 	C7, D7,
 };
 
-const __flash uint8_t tones_morse[2] = {
+const __flash uint16_t tones_morse[2] = {
 	0, D5,
 };