Allow continuous tone frequency changes

Fixes #121
Supersedes #185

Redo the PIO program to allow the tone generator on a pin to be updated
without interruption, at waveform boundaries.  This allows for things like
sirens or slurs to be implemented simply.

Use an alarm, not the PIO hardware, to manage time-limited tones().

Add a simple siren example.

Author: earlephilhower

cores/rp2040/Tone.cpp

@@ -28,16 +28,24 @@ typedef struct {
     pin_size_t pin;
     PIO pio;
     int sm;
+    alarm_id_t alarm;
 } Tone;
 
 // Keep std::map safe for multicore use
 auto_init_mutex(_toneMutex);
 
-
-#include "tone.pio.h"
-static PIOProgram _tonePgm(&tone_program);
+#include "tone2.pio.h"
+static PIOProgram _tone2Pgm(&tone2_program);
 static std::map<pin_size_t, Tone *> _toneMap;
 
+int64_t _stopTonePIO(alarm_id_t id, void *user_data) {
+    (void) id;
+    Tone *tone = (Tone *)user_data;
+    tone->alarm = 0;
+    pio_sm_set_enabled(tone->pio, tone->sm, false);
+    return 0;
+}
+
 void tone(uint8_t pin, unsigned int frequency, unsigned long duration) {
     if (pin > 29) {
         DEBUGCORE("ERROR: Illegal pin in tone (%d)\n", pin);
@@ -58,32 +66,36 @@ void tone(uint8_t pin, unsigned int frequency, unsigned long duration) {
     if (us < 5) {
         us = 5;
     }
-    // Even phases run forever, odd phases end after count...so ensure its odd
-    int phases = duration ? (duration * 1000 / us) | 1 : 2;
     auto entry = _toneMap.find(pin);
-    if (entry != _toneMap.end()) {
-        noTone(pin);
-    }
-
-    auto newTone = new Tone();
-    newTone->pin = pin;
-    pinMode(pin, OUTPUT);
-    int off;
-    if (!_tonePgm.prepare(&newTone->pio, &newTone->sm, &off)) {
-        DEBUGCORE("ERROR: tone unable to start, out of PIO resources\n");
-        // ERROR, no free slots
-        delete newTone;
-        return;
+    Tone *newTone;
+    if (entry == _toneMap.end()) {
+        newTone = new Tone();
+        newTone->pin = pin;
+        pinMode(pin, OUTPUT);
+        int off;
+        if (!_tone2Pgm.prepare(&newTone->pio, &newTone->sm, &off)) {
+            DEBUGCORE("ERROR: tone unable to start, out of PIO resources\n");
+            // ERROR, no free slots
+            delete newTone;
+            return;
+        }
+        tone2_program_init(newTone->pio, newTone->sm, off, pin);
+        newTone->alarm = 0;
+    } else {
+        newTone = entry->second;
+        if (newTone->alarm) {
+            cancel_alarm(newTone->alarm);
+            newTone->alarm = 0;
+        }
     }
-    tone_program_init(newTone->pio, newTone->sm, off, pin);
-    pio_sm_set_enabled(newTone->pio, newTone->sm, false);
     pio_sm_put_blocking(newTone->pio, newTone->sm, RP2040::usToPIOCycles(us));
-    pio_sm_exec(newTone->pio, newTone->sm, pio_encode_pull(false, false));
-    pio_sm_exec(newTone->pio, newTone->sm, pio_encode_out(pio_isr, 32));
     pio_sm_set_enabled(newTone->pio, newTone->sm, true);
-    pio_sm_put_blocking(newTone->pio, newTone->sm, phases);
 
     _toneMap.insert({pin, newTone});
+
+    if (duration) {
+        newTone->alarm = add_alarm_in_ms(duration, _stopTonePIO, (void *)newTone, true);
+    }
 }
 
 void noTone(uint8_t pin) {
@@ -95,6 +107,10 @@ void noTone(uint8_t pin) {
     }
     auto entry = _toneMap.find(pin);
     if (entry != _toneMap.end()) {
+        if (entry->second->alarm) {
+            cancel_alarm(entry->second->alarm);
+            entry->second->alarm = 0;
+        }
         pio_sm_set_enabled(entry->second->pio, entry->second->sm, false);
         pio_sm_unclaim(entry->second->pio, entry->second->sm);
         delete entry->second;

cores/rp2040/tone.pio.h

@@ -1,4 +1,4 @@
-; Tone for the Raspberry Pi Pico RP2040
+; Tone2 for the Raspberry Pi Pico RP2040
 ;
 ; Copyright (c) 2021 Earle F. Philhower, III <[email protected]>
 ;
@@ -18,32 +18,35 @@
 
 ; Side-set pin 0 is used for Tone output
 
-.program tone
+; OSR == Halfcycle count
+
+.program tone2
 .side_set 1 opt
 
-    pull
-    mov x, osr
+    pull                     ; TXFIFO -> OSR, or X -> OSR if no new period
+    mov x, osr               ; OSR -> X
 
 high:
-    mov y, isr      side 1
+    pull noblock             ; Potentially grab new HALFCYCLECOUNT, OTW copy from backup in X
+    mov x, osr               ; OSR -> X
+    mov y, osr      side 1   ; HALFCYCLECOUNT -> Y
 highloop:
-    jmp y-- highloop
-
-    jmp x-- low
+    jmp y-- highloop         ; while (y--) { /* noop delay */ }
 
 low:
-    mov y, isr      side 0
+    mov y, osr      side 0   ; HALFCYCLECOUNT -> Y
 lowloop:
-    jmp y-- lowloop
+    jmp y-- lowloop          ; while (y--) { /* noop delay */ }
 
-    jmp x-- high
+    jmp high                 ; GOTO high
 
 % c-sdk {
-static inline void tone_program_init(PIO pio, uint sm, uint offset, uint pin) {
+static inline void tone2_program_init(PIO pio, uint sm, uint offset, uint pin) {
    pio_gpio_init(pio, pin);
    pio_sm_set_consecutive_pindirs(pio, sm, pin, 1, true);
-   pio_sm_config c = tone_program_get_default_config(offset);
+   pio_sm_config c = tone2_program_get_default_config(offset);
    sm_config_set_sideset_pins(&c, pin);
    pio_sm_init(pio, sm, offset, &c);
 }
 %}
+

cores/rp2040/tone.pio renamed to cores/rp2040/tone2.pio

@@ -0,0 +1,53 @@
+// -------------------------------------------------- //
+// This file is autogenerated by pioasm; do not edit! //
+// -------------------------------------------------- //
+
+#if !PICO_NO_HARDWARE
+#include "hardware/pio.h"
+#endif
+
+// ----- //
+// tone2 //
+// ----- //
+
+#define tone2_wrap_target 0
+#define tone2_wrap 8
+
+static const uint16_t tone2_program_instructions[] = {
+    //     .wrap_target
+    0x80a0, //  0: pull   block
+    0xa027, //  1: mov    x, osr
+    0x8080, //  2: pull   noblock
+    0xa027, //  3: mov    x, osr
+    0xb847, //  4: mov    y, osr          side 1
+    0x0085, //  5: jmp    y--, 5
+    0xb047, //  6: mov    y, osr          side 0
+    0x0087, //  7: jmp    y--, 7
+    0x0002, //  8: jmp    2
+    //     .wrap
+};
+
+#if !PICO_NO_HARDWARE
+static const struct pio_program tone2_program = {
+    .instructions = tone2_program_instructions,
+    .length = 9,
+    .origin = -1,
+};
+
+static inline pio_sm_config tone2_program_get_default_config(uint offset) {
+    pio_sm_config c = pio_get_default_sm_config();
+    sm_config_set_wrap(&c, offset + tone2_wrap_target, offset + tone2_wrap);
+    sm_config_set_sideset(&c, 2, true, false);
+    return c;
+}
+
+static inline void tone2_program_init(PIO pio, uint sm, uint offset, uint pin) {
+    pio_gpio_init(pio, pin);
+    pio_sm_set_consecutive_pindirs(pio, sm, pin, 1, true);
+    pio_sm_config c = tone2_program_get_default_config(offset);
+    sm_config_set_sideset_pins(&c, pin);
+    pio_sm_init(pio, sm, offset, &c);
+}
+
+#endif
+

cores/rp2040/tone2.pio.h

@@ -0,0 +1,13 @@
+/* Simple annoying siren example using tone() */
+/* Released to the public domain by Earle F. Philhower, III */
+
+#define TONEPIN 7
+
+void setup() {
+}
+
+void loop() {
+  for (int i = 100; i < 10000; i += 5) {
+    tone(TONEPIN, i);
+  }
+}