Move to shared TIMER1 infrastructure, add Steppers

Remove and rewrite all the parts of the core/libraries using TIMER1
and consolidate into a single, shared waveform generation interrupt
structure.  Tone, analogWrite(), Servo all now just call into this
shared resource to perform their tasks.

This setup enables multiple tones, analogWrites, servos, and stepper
motors to be controlled with reasonable accuracy.  It uses both TIMER1
and the internal ESP cycle counter to handle timing of waveform edges.
TIMER1 is used in non-reload mode and only edges cause interrupts.  The
interrupt is started and stopped as required, minimizing overhead when
these features are not being used.

Adds in control of DRV8825 or A4988 interfaces stepper motors to the
timer infrastructure.  The interrupt handles acceleration and velocity
of stepper pulses including jerk (dA/dt) calculations, but it is up
to the user application to do path planning and generate S-curve
accelerations.  All stepper DIR pins are connected together, and then
the STEP from each stepper interface board is routed to an individual
pin.  For motions which involve multiple steppers, there is an option
to wait before beginning the next stepper motion until all active
steppers have completed their moves (i.e. moving to an X, Y where there
may be 1-2us delay between the X arrival and Y arrival).

A generic "startWaveform(pin, high-US, low-US, runtime-US)" and
"stopWaveform(pin)" allow for further types of interfaces.

Using a simple USB DSO shows that with only a single channel running,
a "tone(1000)" generates a waveform of 999.8Hz (500.1us per high/low).
Running additional generators or steppers will potentially increase the
jitter.

The implementation also is limited in the time of the shortest pulse
it can generate (mostly an issue for analogWrite at values <1% or
>99% of the scale).  Presently measurements of ~2-3us are seen on
the shortest of pulses.  There is no optimization to allow generating
two edges on a single interrupt, which leads to this minimum pulse
width.

The current implementation was written focusing on readability and
flexibility, not squeezing every cycle out of interrupt loops. There
are probably many places where the code could be optimized (after it's
fully validated!) to reduce CPU load and timing errors.

Author: earlephilhower

cores/esp8266/Tone.cpp

@@ -3,7 +3,7 @@
 
   A Tone Generator Library for the ESP8266
 
-  Copyright (c) 2016 Ben Pirt. All rights reserved.
+  Original Copyright (c) 2016 Ben Pirt. All rights reserved.
   This file is part of the esp8266 core for Arduino environment.
 
   This library is free software; you can redistribute it and/or
@@ -22,115 +22,36 @@
 */
 
 #include "Arduino.h"
-#include "pins_arduino.h"
+#include "core_esp8266_waveform.h"
 
-#define AVAILABLE_TONE_PINS 1
-const uint8_t tone_timers[] = { 1 };
-static uint8_t tone_pins[AVAILABLE_TONE_PINS] = { 255, };
-static long toggle_counts[AVAILABLE_TONE_PINS] = { 0, };
-#define T1INDEX 0
+// Which pins have a tone running on them?
+static uint32_t _toneMap = 0;
 
-void t1IntHandler();
-
-static int8_t toneBegin(uint8_t _pin) {
-  int8_t _index = -1;
-
-  // if we're already using the pin, reuse it.
-  for (int i = 0; i < AVAILABLE_TONE_PINS; i++) {
-    if (tone_pins[i] == _pin) {
-      return i;
-    }
+void tone(uint8_t _pin, unsigned int frequency, unsigned long duration) {
+  if (_pin > 16) {
+    return;
   }
 
-  // search for an unused timer.
-  for (int i = 0; i < AVAILABLE_TONE_PINS; i++) {
-    if (tone_pins[i] == 255) {
-      tone_pins[i] = _pin;
-      _index = i;
-      break;
-    }
+  if (frequency == 0) {
+    noTone(_pin);
+    return;
   }
 
-  return _index;
-}
-
-// frequency (in hertz) and duration (in milliseconds).
-void tone(uint8_t _pin, unsigned int frequency, unsigned long duration) {
-  int8_t _index;
-
-  _index = toneBegin(_pin);
-
-  if (_index >= 0) {
-    // Set the pinMode as OUTPUT
-    pinMode(_pin, OUTPUT);
-
-    // Alternate handling of zero freqency to avoid divide by zero errors
-    if (frequency == 0)
-    {
-        noTone(_pin);
-        return;
-    }
-
-    // Calculate the toggle count
-    if (duration > 0) {
-      toggle_counts[_index] = 2 * frequency * duration / 1000;
-    } else {
-      toggle_counts[_index] = -1;
-    }
-
-    // set up the interrupt frequency
-    switch (tone_timers[_index]) {
-      case 0:
-        // Not currently supported
-        break;
-
-      case 1:
-        timer1_disable();
-        timer1_isr_init();
-        timer1_attachInterrupt(t1IntHandler);
-        timer1_enable(TIM_DIV1, TIM_EDGE, TIM_LOOP);
-        timer1_write((clockCyclesPerMicrosecond() * 500000) / frequency);
-        break;
-    }
+  uint32_t halfCycle = 500000L / frequency;
+  if (halfCycle < 100) {
+    halfCycle = 100;
   }
-}
-
-void disableTimer(uint8_t _index) {
-  tone_pins[_index] = 255;
 
-  switch (tone_timers[_index]) {
-    case 0:
-      // Not currently supported
-      break;
-
-    case 1:
-      timer1_disable();
-      break;
+  if (startWaveform(_pin, halfCycle, halfCycle, (uint32_t) duration * 1000)) {
+    _toneMap |= 1 << _pin;
   }
 }
 
 void noTone(uint8_t _pin) {
-  for (int i = 0; i < AVAILABLE_TONE_PINS; i++) {
-    if (tone_pins[i] == _pin) {
-      tone_pins[i] = 255;
-      disableTimer(i);
-      break;
-    }
-  }
-  digitalWrite(_pin, LOW);
-}
-
-ICACHE_RAM_ATTR void t1IntHandler() {
-  if (toggle_counts[T1INDEX] != 0){
-    // toggle the pin
-    digitalWrite(tone_pins[T1INDEX], toggle_counts[T1INDEX] % 2);
-    toggle_counts[T1INDEX]--;
-    // handle the case of indefinite duration
-    if (toggle_counts[T1INDEX] < -2){
-      toggle_counts[T1INDEX] = -1;
-    }
-  }else{
-    disableTimer(T1INDEX);
-    digitalWrite(tone_pins[T1INDEX], LOW);
+  if (_pin > 16) {
+    return;
   }
+  stopWaveform(_pin);
+  _toneMap &= ~(1 << _pin);
+  digitalWrite(_pin, 0);
 }