add comments for tone max frequency limit

Tech-TX · Tech-TX · commit f5000ad78f87 · 2020-03-31T20:23:51.000-05:00
diff --git a/cores/esp8266/Tone.cpp b/cores/esp8266/Tone.cpp
@@ -35,10 +35,12 @@ static void _startTone(uint8_t _pin, uint32_t high, uint32_t low, unsigned long
 
   pinMode(_pin, OUTPUT);
 
-  high = std::max(high, (uint32_t)100);
-  low = std::max(low, (uint32_t)100);
+  high = std::max(high, (uint32_t)100);  // 5KHz maximum tone for Arduino compatibility
+  low = std::max(low, (uint32_t)100);    // (100us high + 100us low period = 5KHz)
 
-  if (startWaveform(_pin, high, low, (uint32_t) duration * 1000)) {
+  duration *= 1000UL;
+  duration -= duration % (high + low);
+  if (startWaveform(_pin, high, low, duration)) {
     _toneMap |= 1 << _pin;
   }
 }

Original file line number	Diff line number	Diff line change
`@@ -35,10 +35,12 @@ static void _startTone(uint8_t _pin, uint32_t high, uint32_t low, unsigned long`
`35`	`35`
`36`	`36`	`pinMode(_pin, OUTPUT);`
`37`	`37`
`38`		`- high = std::max(high, (uint32_t)100);`
`39`		`- low = std::max(low, (uint32_t)100);`
	`38`	`+ high = std::max(high, (uint32_t)100); // 5KHz maximum tone for Arduino compatibility`
	`39`	`+ low = std::max(low, (uint32_t)100); // (100us high + 100us low period = 5KHz)`
`40`	`40`
`41`		`- if (startWaveform(_pin, high, low, (uint32_t) duration * 1000)) {`
	`41`	`+ duration *= 1000UL;`
	`42`	`+ duration -= duration % (high + low);`
	`43`	`+ if (startWaveform(_pin, high, low, duration)) {`
`42`	`44`	`_toneMap \|= 1 << _pin;`
`43`	`45`	`}`
`44`	`46`	`}`