Started following some tutorial on att85 usi. Downloaded example code from make avr book.

2022-09-20 01:08:01 -04:00
parent d0cbc0000e
commit 361a828c46
295 changed files with 68746 additions and 0 deletions
--- a/Examples/Chapter13_Advanced-PWM-Tricks/adsr/adsr.c
+++ b/Examples/Chapter13_Advanced-PWM-Tricks/adsr/adsr.c
@@ -0,0 +1,86 @@
+/*
+   Direct-digital synthesis
+   ADSR Dynamic Volume Envelope Demo
+*/
+
+// ------- Preamble -------- //
+#include "adsr.h"             /* Defines, includes, and init functions */
+
+int main(void) {
+
+  // -------- Inits --------- //
+
+  uint16_t accumulator = 0;
+  uint8_t volume = 0;
+  uint16_t noteClock = 0;
+  uint16_t tuningWord = C1;
+
+  uint8_t waveStep;
+  int16_t mixer=0;
+  char serialInput;
+
+  clock_prescale_set(clock_div_1);                  /* CPU clock 8 MHz */
+  initTimer0();
+  initUSART();
+  printString("  Serial Synth\r\n");
+  printString("Notes: asdfghjkl;'\r\n");
+
+  SPEAKER_DDR |= (1 << SPEAKER);                     /* speaker output */
+
+  // ------ Event loop ------ //
+  while (1) {
+
+    // Set PWM output
+    loop_until_bit_is_set(TIFR0, TOV0);    /* wait for timer0 overflow */
+    OCR0A = 128 + (uint8_t) mixer;
+    TIFR0 |= (1 << TOV0);                    /* reset the overflow bit */
+
+    // Update the DDS
+    accumulator += tuningWord;
+    waveStep = accumulator >> 8;
+    mixer = fullTriangle[waveStep] * volume;
+    mixer = mixer >> 5;
+
+                                  /* Input processed here: check USART */
+    if (bit_is_set(UCSR0A, RXC0)) {
+      serialInput = UDR0;                        /* read in from USART */
+      tuningWord = lookupPitch(serialInput);
+      noteClock = 1;
+    }
+
+                                          /* Dynamic Volume stuff here */
+    if (noteClock) {                   /* if noteClock already running */
+      noteClock++;
+      if (noteClock < ATTACK_TIME) {                         /* attack */
+                              /* wait until time to increase next step */
+        if (noteClock > ATTACK_RATE * volume) {
+          if (volume < 31) {
+            volume++;
+          }
+        }
+      }
+      else if (noteClock < DECAY_TIME) {                      /* decay */
+        if ((noteClock - ATTACK_TIME) >
+            (FULL_VOLUME - volume) * DECAY_RATE) {
+          if (volume > SUSTAIN_LEVEL) {
+            volume--;
+          }
+        }
+      }
+      else if (noteClock > RELEASE_TIME) {                  /* release */
+        if ((noteClock - RELEASE_TIME) >
+            (SUSTAIN_LEVEL - volume) * RELEASE_RATE) {
+          if (volume > 0) {
+            volume--;
+          }
+          else {
+            noteClock = 0;
+          }
+        }
+      }
+    }
+
+
+  }                                                  /* End event loop */
+  return 0;                            /* This line is never reached */
+}