refactor: support higher modulation frequencies and better precision (#4)

Support higher modulation frequencies and get better precision without the need for calibration.

---------

Co-authored-by: Daniel Wallner <[email protected]>

Author: zehnm

src/IRsend.cpp

@@ -26,7 +26,7 @@
 ///  i.e. If not, assume a 100% duty cycle. Ignore attempts to change the
 ///  duty cycle etc.
 IRsend::IRsend(uint16_t IRsendPin, bool inverted, bool use_modulation)
-    : IRpin(IRsendPin), periodOffset(kPeriodOffset) {
+    : IRpin(IRsendPin) {
   if (inverted) {
     outputOn = LOW;
     outputOff = HIGH;
@@ -54,7 +54,7 @@ IRsend::IRsend(uint16_t IRsendPin, bool inverted, bool use_modulation)
 /// @param[in] w1tc_mask mask for clearing GPIOs for a logical 1 output.
 ///  Required if some outputs are inverted.
 IRsend::IRsend(bool use_modulation, int64_t w1ts_mask, uint64_t w1tc_mask) :
-    periodOffset(kPeriodOffset), _irPinMaskEnabled(true) {
+    _irPinMaskEnabled(true) {
   IRpin = static_cast<int32_t>(w1ts_mask);
   _w1ts_mask_upper = static_cast<int32_t>(w1ts_mask >> 32);
   _w1tc_mask_lower = static_cast<int32_t>(w1tc_mask);
@@ -152,18 +152,14 @@ void IRsend::ledOn() {
 
 /// Calculate the period for a given frequency.
 /// @param[in] hz Frequency in Hz.
-/// @param[in] use_offset Should we use the calculated offset or not?
 /// @return nr. of uSeconds.
 /// @note (T = 1/f)
-uint32_t IRsend::calcUSecPeriod(uint32_t hz, bool use_offset) {
+uint32_t IRsend::calcUSecPeriod(uint32_t hz) {
   if (hz == 0) hz = 1;  // Avoid Zero hz. Divide by Zero is nasty.
   uint32_t period =
       (1000000UL + hz / 2) / hz;  // The equiv of round(1000000/hz).
-  // Apply the offset and ensure we don't result in a <= 0 value.
-  if (use_offset)
-    return std::max(static_cast<uint32_t>(1), period + periodOffset);
-  else
-    return std::max(static_cast<uint32_t>(1), period);
+  // Ensure we don't result in a <= 0 value.
+  return std::max(static_cast<uint32_t>(1), period);
 }
 
 /// Set the output frequency modulation and duty cycle.
@@ -188,11 +184,34 @@ void IRsend::enableIROut(uint32_t freq, uint8_t duty) {
 #ifdef UNIT_TEST
   _freq_unittest = freq;
 #endif  // UNIT_TEST
+
+#ifndef UNIT_TEST
+  _fractionalBits = 14;
+
+  // Maximum signed value that fits.
+  uint32_t maxValue = 0x7FFF >> _fractionalBits;
+  uint32_t period = calcUSecPeriod(freq);
+
+  // Decrement the number of fractional bits until the period fits.
+  while (maxValue < period) {
+    --_fractionalBits;
+    maxValue = 0x7FFF >> _fractionalBits;
+  }
+
+  uint32_t fixedPointPeriod = ((1000000ULL << _fractionalBits) + freq / 2)
+                              / freq;
+
+  // Nr. of uSeconds the LED will be on per pulse.
+  onTimePeriod = (fixedPointPeriod * _dutycycle) / kDutyMax;
+  // Nr. of uSeconds the LED will be off per pulse.
+  offTimePeriod = fixedPointPeriod - onTimePeriod;
+#else
   uint32_t period = calcUSecPeriod(freq);
   // Nr. of uSeconds the LED will be on per pulse.
   onTimePeriod = (period * _dutycycle) / kDutyMax;
   // Nr. of uSeconds the LED will be off per pulse.
   offTimePeriod = period - onTimePeriod;
+#endif
 }
 
 #if ALLOW_DELAY_CALLS
@@ -253,6 +272,67 @@ uint16_t IRsend::mark(uint16_t usec) {
   // Not simple, so do it assuming frequency modulation.
   uint16_t counter = 0;
   IRtimer usecTimer = IRtimer();
+#ifndef UNIT_TEST
+#if SEND_BANG_OLUFSEN && ESP8266 && F_CPU < 160000000L
+  // Free running loop to attempt to get close to the 455 kHz required by
+  // Bang & Olufsen.
+  // Define BANG_OLUFSEN_CHECK_MODULATION temporarily to test frequency and
+  // time.
+  // Runs at ~300 kHz on an 80 MHz ESP8266.
+  // This is far from ideal but works if the transmitter is close enough.
+  uint32_t periodUInt = (onTimePeriod + offTimePeriod) >> _fractionalBits;
+  periodUInt = std::max(static_cast<uint32_t>(1), periodUInt);
+  if (periodUInt <= 5) {
+    // Assume we can at least run for this number of periods.
+    uint32_t nextCheck = usec / periodUInt / 2;
+    for (;;) {  // nextStop is not updated in this loop.
+      ledOn();
+      ledOff();
+      counter++;
+      if (counter >= nextCheck) {
+        uint32_t now = usecTimer.elapsed();
+        int32_t timeLeft = usec - now;
+        if (timeLeft <= 1) {
+          return counter;
+        }
+        uint32_t periodsToEnd = counter * timeLeft / now;
+        // Check again when we are half way closer to the end.
+        nextCheck = (periodsToEnd >> 2) + counter;
+      }
+    }
+  }
+#endif
+
+  // Use absolute time for zero drift (but slightly uneven period).
+  // Using IRtimer.elapsed() instead of _delayMicroseconds is better for short
+  // period times.
+  // Maxed out at ~190 kHz on an 80 MHz ESP8266.
+  // Maxed out at ~460 kHz on ESP32.
+  // Must be 32 bits to not overflow when usec is near max.
+  uint32_t nextStop = 0;
+  // Loop until we've met/exceeded our required time.
+  while ((nextStop >> _fractionalBits) < usec) {
+    ledOn();
+    nextStop += onTimePeriod;
+    uint32_t nextStopUInt = std::min(nextStop >>
+                            _fractionalBits, static_cast<uint32_t>(usec));
+    while (usecTimer.elapsed() < nextStopUInt) {}
+    ledOff();
+    counter++;
+    nextStop += offTimePeriod;
+    nextStopUInt = std::min(nextStop >>
+                   _fractionalBits, static_cast<uint32_t>(usec));
+    uint32_t now = usecTimer.elapsed();
+    int32_t delay = nextStopUInt - now;
+    if (delay > 0) {
+      while (usecTimer.elapsed() < nextStopUInt) {}
+    } else {
+      // This means we ran past nextStop and need to reset to actual time to
+      // avoid playing catch-up with a far too short period.
+      nextStop = (now << _fractionalBits) + (offTimePeriod >> 1);
+    }
+  }
+#else
   // Cache the time taken so far. This saves us calling time, and we can be
   // assured that we can't have odd math problems. i.e. unsigned under/overflow.
   uint32_t elapsed = usecTimer.elapsed();
@@ -273,6 +353,7 @@ uint16_t IRsend::mark(uint16_t usec) {
                  static_cast<uint32_t>(offTimePeriod)));
     elapsed = usecTimer.elapsed();  // Update & recache the actual elapsed time.
   }
+#endif
   return counter;
 }
 
@@ -296,7 +377,7 @@ void IRsend::space(uint32_t time) {
 int8_t IRsend::calibrate(uint16_t hz) {
   if (hz < 1000)  // Were we given kHz? Supports the old call usage.
     hz *= 1000;
-  periodOffset = 0;  // Turn off any existing offset while we calibrate.
+  int8_t periodOffset = 0;
   enableIROut(hz);
   IRtimer usecTimer = IRtimer();  // Start a timer *just* before we do the call.
   uint16_t pulses = mark(UINT16_MAX);  // Generate a PWM of 65,535 us. (Max.)

src/IRsend.h

@@ -22,17 +22,6 @@
 // Constants
 // Offset (in microseconds) to use in Period time calculations to account for
 // code excution time in producing the software PWM signal.
-#if defined(ESP32)
-// Calculated on a generic ESP-WROOM-32 board with v3.2-18 SDK @ 240MHz
-const int8_t kPeriodOffset = -2;
-#elif (defined(ESP8266) && F_CPU == 160000000L)  // NOLINT(whitespace/parens)
-// Calculated on an ESP8266 NodeMCU v2 board using:
-// v2.6.0 with v2.5.2 ESP core @ 160MHz
-const int8_t kPeriodOffset = -2;
-#else  // (defined(ESP8266) && F_CPU == 160000000L)
-// Calculated on ESP8266 Wemos D1 mini using v2.4.1 with v2.4.0 ESP core @ 40MHz
-const int8_t kPeriodOffset = -5;
-#endif  // (defined(ESP8266) && F_CPU == 160000000L)
 const uint8_t kDutyDefault = 50;  // Percentage
 const uint8_t kDutyMax = 100;     // Percentage
 // delayMicroseconds() is only accurate to 16383us.
@@ -940,13 +929,13 @@ class IRsend {
 #else
   uint32_t _freq_unittest;
 #endif  // UNIT_TEST
-  uint16_t onTimePeriod;
-  uint16_t offTimePeriod;
+  uint16_t onTimePeriod;  // Fixed point.
+  uint16_t offTimePeriod;  // Fixed point.
+  uint8_t _fractionalBits;  // Number of fractional bits in on/offTimePeriod.
   uint32_t IRpin;
-  int8_t periodOffset;
   uint8_t _dutycycle;
   bool modulation;
-  uint32_t calcUSecPeriod(uint32_t hz, bool use_offset = true);
+  uint32_t calcUSecPeriod(uint32_t hz);
 #if SEND_SONY
   void _sendSony(const uint64_t data, const uint16_t nbits,
                  const uint16_t repeat, const uint16_t freq);

src/IRtimer.cpp

@@ -31,10 +31,7 @@ uint32_t IRtimer::elapsed() {
 #else
   uint32_t now = _IRtimer_unittest_now;
 #endif
-  if (start <= now)      // Check if the system timer has wrapped.
-    return now - start;  // No wrap.
-  else
-    return UINT32_MAX - start + now;  // Has wrapped.
+  return now - start;  // Wrap safe.
 }
 
 /// Add time to the timer to simulate elapsed time.
@@ -64,10 +61,7 @@ uint32_t TimerMs::elapsed() {
 #else
   uint32_t now = _TimerMs_unittest_now;
 #endif
-  if (start <= now)      // Check if the system timer has wrapped.
-    return now - start;  // No wrap.
-  else
-    return UINT32_MAX - start + now;  // Has wrapped.
+  return now - start;  // Wrap safe.
 }
 
 /// Add time to the timer to simulate elapsed time.

src/ir_GlobalCache.cpp

@@ -35,7 +35,7 @@ const uint8_t kGlobalCacheStartIndex = kGlobalCacheRptStartIndex + 1;
 void IRsend::sendGC(uint16_t buf[], uint16_t len) {
   uint16_t hz = buf[kGlobalCacheFreqIndex];  // GC frequency is in Hz.
   enableIROut(hz);
-  uint32_t periodic_time = calcUSecPeriod(hz, false);
+  uint32_t periodic_time = calcUSecPeriod(hz);
   uint8_t emits =
       std::min(buf[kGlobalCacheRptIndex],
                static_cast<uint16_t>(kGlobalCacheMaxRepeat));

src/ir_Pronto.cpp

@@ -73,7 +73,7 @@ bool IRsend::sendPronto(uint16_t data[], uint16_t len, uint16_t repeat) {
   uint16_t seq_1_start = kProntoDataOffset;
   uint16_t seq_2_start = kProntoDataOffset + seq_1_len;
 
-  uint32_t periodic_time_x10 = calcUSecPeriod(hz / 10, false);
+  uint32_t periodic_time_x10 = calcUSecPeriod(hz / 10);
 
   // Normal (1st sequence) case.
   // Is there a first (normal) sequence to send?

test/IRsend_test.cpp

@@ -239,18 +239,18 @@ TEST(TestLowLevelSend, MarkFrequencyModulationAt38kHz) {
 
   irsend.reset();
   irsend.enableIROut(38000, 50);
-  EXPECT_EQ(5, irsend.mark(100));
+  EXPECT_EQ(4, irsend.mark(100));
   EXPECT_EQ(
-      "[On]10usecs[Off]11usecs[On]10usecs[Off]11usecs[On]10usecs[Off]11usecs"
-      "[On]10usecs[Off]11usecs[On]10usecs[Off]6usecs",
+      "[On]13usecs[Off]13usecs[On]13usecs[Off]13usecs[On]13usecs[Off]13usecs"
+      "[On]13usecs[Off]9usecs",
       irsend.low_level_sequence);
 
   irsend.reset();
   irsend.enableIROut(38000, 33);
-  EXPECT_EQ(5, irsend.mark(100));
+  EXPECT_EQ(4, irsend.mark(100));
   EXPECT_EQ(
-      "[On]6usecs[Off]15usecs[On]6usecs[Off]15usecs[On]6usecs[Off]15usecs"
-      "[On]6usecs[Off]15usecs[On]6usecs[Off]10usecs",
+      "[On]8usecs[Off]18usecs[On]8usecs[Off]18usecs[On]8usecs[Off]18usecs"
+      "[On]8usecs[Off]14usecs",
       irsend.low_level_sequence);
 
   irsend.reset();
@@ -266,18 +266,18 @@ TEST(TestLowLevelSend, MarkFrequencyModulationAt36_7kHz) {
 
   irsend.reset();
   irsend.enableIROut(36700, 50);
-  EXPECT_EQ(5, irsend.mark(100));
+  EXPECT_EQ(4, irsend.mark(100));
   EXPECT_EQ(
-      "[On]11usecs[Off]11usecs[On]11usecs[Off]11usecs[On]11usecs[Off]11usecs"
-      "[On]11usecs[Off]11usecs[On]11usecs[Off]1usecs",
+      "[On]13usecs[Off]14usecs[On]13usecs[Off]14usecs[On]13usecs[Off]14usecs"
+      "[On]13usecs[Off]6usecs",
       irsend.low_level_sequence);
 
   irsend.reset();
   irsend.enableIROut(36700, 33);
-  EXPECT_EQ(5, irsend.mark(100));
+  EXPECT_EQ(4, irsend.mark(100));
   EXPECT_EQ(
-      "[On]7usecs[Off]15usecs[On]7usecs[Off]15usecs[On]7usecs[Off]15usecs"
-      "[On]7usecs[Off]15usecs[On]7usecs[Off]5usecs",
+      "[On]8usecs[Off]19usecs[On]8usecs[Off]19usecs[On]8usecs[Off]19usecs"
+      "[On]8usecs[Off]11usecs",
       irsend.low_level_sequence);
 
   irsend.reset();
@@ -293,18 +293,18 @@ TEST(TestLowLevelSend, MarkFrequencyModulationAt40kHz) {
 
   irsend.reset();
   irsend.enableIROut(40000, 50);
-  EXPECT_EQ(5, irsend.mark(100));
+  EXPECT_EQ(4, irsend.mark(100));
   EXPECT_EQ(
-      "[On]10usecs[Off]10usecs[On]10usecs[Off]10usecs[On]10usecs[Off]10usecs"
-      "[On]10usecs[Off]10usecs[On]10usecs[Off]10usecs",
+      "[On]12usecs[Off]13usecs[On]12usecs[Off]13usecs[On]12usecs[Off]13usecs"
+      "[On]12usecs[Off]13usecs",
       irsend.low_level_sequence);
 
   irsend.reset();
   irsend.enableIROut(40000, 33);
-  EXPECT_EQ(5, irsend.mark(100));
+  EXPECT_EQ(4, irsend.mark(100));
   EXPECT_EQ(
-      "[On]6usecs[Off]14usecs[On]6usecs[Off]14usecs[On]6usecs[Off]14usecs"
-      "[On]6usecs[Off]14usecs[On]6usecs[Off]14usecs",
+      "[On]8usecs[Off]17usecs[On]8usecs[Off]17usecs[On]8usecs[Off]17usecs"
+      "[On]8usecs[Off]17usecs",
       irsend.low_level_sequence);
 
   irsend.reset();