fixed imprecisse timing on SAMD21 (Arduino Zero)

.arduino-ci.yaml

@@ -0,0 +1,11 @@
+compile:
+  platforms:
+    - uno
+    - due
+    - zero
+    - leonardo
+    - m4
+    - esp32
+    #- esp8266
+    - mega2560
+    - nano_every

.github/workflows/arduino-lint.yaml

@@ -0,0 +1,16 @@
+---
+name: arduino-lint
+
+on: [push, pull_request]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        # https://github.com/actions/checkout
+      - uses: arduino/arduino-lint-action@v1
+        # https://github.com/arduino/arduino-lint-action
+        with:
+          library-manager: update
+          compliance: strict

.github/workflows/arduino_ci.yaml

@@ -0,0 +1,13 @@
+---
+name: arduino_ci
+
+on: [push, pull_request]
+
+jobs:
+  arduino_ci:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        # https://github.com/actions/checkout
+      - uses: Arduino-CI/action@stable-1.x
+        # https://github.com/marketplace/actions/arduino_ci

contributors.txt

@@ -1,3 +1,4 @@
 Naguissa - https://github.com/Naguissa
 svlPanelMaker - https://github.com/svlPanelMaker - SAMD21 timing issue fix
 Raf (Raffaele Rialdi) - https://github.com/raffaeler - ESP32 hardware timer (better precission than ticker library)
+Daniel Mohr - https://github.com/daniel-mohr - SAMD21 timing issue fix

library.properties

@@ -1,5 +1,5 @@
 name=uTimerLib
-version=1.7.1
+version=1.7.2
 author=Naguissa <naguissa@foroelectro.net>
 maintainer=Naguissa <naguissa@foroelectro.net>
 sentence=Tiny and cross-device compatible timer library

src/hardware/uTimerLib.SAMD21.cpp

@@ -52,26 +52,41 @@
 
 		Prescaler:
 		Prescalers: GCLK_TC, GCLK_TC/2, GCLK_TC/4, GCLK_TC/8, GCLK_TC/16, GCLK_TC/64, GCLK_TC/256, GCLK_TC/1024
-		Base frequency: 84MHz
+		Base frequency: 48MHz
 
 		We will use TCC2, as there're some models with only 3 timers (regular models have 5 TCs)
 
 		REMEMBER! 16 bit counter!!!
 
 
 		Name			Prescaler	Freq		Base Delay		Overflow delay
-		GCLK_TC			   1		 48MHz		0,020833333us	   1365,333333333us;    1,365333333333ms
-		GCLK_TC/2		   2		 24MHz		0,041666667us	   2730,666666667us;    2,730666666667ms
-		GCLK_TC/4		   4		 12MHz		0,083333333us	   5461,333333333us;    5,461333333333ms
-		GCLK_TC/8		   8		  6MHz		0,166666667us	  10922,666666667us;   10,922666666667ms
-		GCLK_TC/16		  16		  3MHz		0,333333333us	  21845,333333333us;   21,845333333333ms
-		GCLK_TC/64		  64		750KHz		1,333333333us	  87381,333311488us;   87,381333311488ms
-		GCLK_TC/256		 256		187,5KHz	5,333333333us	 349525,333311488us;  349,525333311488ms
-		GCLK_TC/1024	1024		46.875Hz	21,333333333us	1398101,333333333us; 1398,101333333333ms; 1,398101333333333s
+		GCLK_TC			   1		 48MHz		~0,020833333us	   1365,3125us;    1,3653125ms
+		GCLK_TC/2		   2		 24MHz		~0,041666667us	   2730,625us;    2,730625ms
+		GCLK_TC/4		   4		 12MHz		~0,083333333us	   5461,25us;    5,46125ms
+		GCLK_TC/8		   8		  6MHz		~0,166666667us	  10922,5us;   10,9225ms
+		GCLK_TC/16		  16		  3MHz		~0,333333333us	  21845us;   21,845ms
+		GCLK_TC/64		  64		750KHz		~1,333333333us	  87380us;   87,380ms
+		GCLK_TC/256		 256		187,5KHz	~5,333333333us	 349520us;  349,52ms
+		GCLK_TC/1024	1024		46.875kHz	~21,333333333us	1398080us; 1398,08ms; 1,39808s
+
+		In general:
+			freq = 48 MHz / prescaler
+			base_delay = 1 / freq
+			overflow_delay = UINT16_MAX * base_delay
 
 		Will be using:
 			GCLK_TC/16 for us
 			GCLK_TC/1024 for s
+
+		GCLK_TC/16:
+		freq = 48 MHz / prescaler = 48 MHz / 16 = 3 MHz
+		base_delay = 1 / freq = 1 / 3e6 s = 1/3 us ~= 0.333333333 us
+		overflow_delay = UINT16_MAX * base_delay = 65535 / 3 us = 21845 us
+
+		GCLK_TC/1024:
+		freq = 48 MHz / prescaler = 48 MHz / 1024 = 46.875 kHz = 46875 Hz
+		base_delay = 1 / freq = 1 / 46875 s = ~= 21.333333333us
+		overflow_delay = UINT16_MAX * base_delay = 65535 / 46875 s = 1.39808 s
 		*/
 
 		// Enable clock for TC
@@ -82,23 +97,23 @@
 		_TC->CTRLA.reg &= ~TC_CTRLA_ENABLE;
 		while (_TC->STATUS.bit.SYNCBUSY == 1); // sync
 
-		// Set Timer counter Mode to 16 bits + Set TC as normal Normal Frq + Prescaler: GCLK_TC/16
-		_TC->CTRLA.reg |= (TC_CTRLA_MODE_COUNT16 + TC_CTRLA_WAVEGEN_NFRQ + TC_CTRLA_PRESCALER_DIV16);
+		// Set Timer counter Mode to 16 bits + Set TC as normal Match Frq + Prescaler: GCLK_TC/16
+		_TC->CTRLA.reg |= (TC_CTRLA_MODE_COUNT16 + TC_CTRLA_WAVEGEN_MFRQ + TC_CTRLA_PRESCALER_DIV16);
 		while (_TC->STATUS.bit.SYNCBUSY == 1); // sync
 
 		if (us > 21845) {
-			__overflows = _overflows = us / 21845.333333333;
-			__remaining = _remaining = ((us - (21845.333333333 * _overflows)) / 0.333333333) + 0.5; // +0.5 is same as round
+			__overflows = _overflows = us / 21845.0;
+			__remaining = _remaining = (us - (21845 * _overflows)) * 3 - 1;
 		} else {
 			__overflows = _overflows = 0;
-			__remaining = _remaining = (us / 0.333333333) + 0.5; // +0.5 is same as round
+			__remaining = _remaining = us * 3 - 1;
 		}
 
 		if (__overflows == 0) {
 			_loadRemaining();
 			_remaining = 0;
 		} else {
-			_TC->CC[0].reg = 65535;
+			_TC->CC[0].reg = UINT16_MAX;
 			_TC->INTENSET.reg = 0;              // disable all interrupts
 			_TC->INTENSET.bit.OVF = 1;          // enable overfollow
 			// Skip: while (_TC->STATUS.bit.SYNCBUSY == 1); // sync
@@ -126,7 +141,7 @@
 		}
 
 		/*
-		GCLK_TC/1024	1024		46.875Hz	21,333333333us	1398101,333333333us; 1398,101333333333ms; 1,398101333333333s
+		GCLK_TC/1024	1024		46.875kHz	~21,333333333us	1398080us; 1398,08ms; 1,39808s
 		*/
 
 		// Enable clock for TC
@@ -137,23 +152,23 @@
 		_TC->CTRLA.reg &= ~TC_CTRLA_ENABLE;
 		while (_TC->STATUS.bit.SYNCBUSY == 1); // sync
 
-		// Set Timer counter Mode to 16 bits + Set TC as normal Normal Frq + Prescaler: GCLK_TC/1024
-		_TC->CTRLA.reg |= (TC_CTRLA_MODE_COUNT16 + TC_CTRLA_WAVEGEN_NFRQ + TC_CTRLA_PRESCALER_DIV1024);
+		// Set Timer counter Mode to 16 bits + Set TC as normal Match Frq + Prescaler: GCLK_TC/1024
+		_TC->CTRLA.reg |= (TC_CTRLA_MODE_COUNT16 + TC_CTRLA_WAVEGEN_MFRQ + TC_CTRLA_PRESCALER_DIV1024);
 		while (_TC->STATUS.bit.SYNCBUSY == 1); // sync
 
 		if (s > 1) {
-			__overflows = _overflows = s / 1.398101333333333;
-			__remaining = _remaining = ((s - (1.398101333333333 * _overflows)) / 0.000021333333333) + 0.5; // +0.5 is same as round
+			__overflows = _overflows = s / 1.39808;
+			__remaining = _remaining = ((s * 100000) % 139808) * 480 / 1024 - 1; // for integer s this is always an integer
 		} else {
 			__overflows = _overflows = 0;
-			__remaining = _remaining = (s / 0.000021333333333) + 0.5; // +0.5 is same as round
+			__remaining = _remaining = s * 46875 - 1;
 		}
 
 		if (__overflows == 0) {
 			_loadRemaining();
 			_remaining = 0;
 		} else {
-			_TC->CC[0].reg = 65535;
+			_TC->CC[0].reg = UINT16_MAX;
 			_TC->INTENSET.reg = 0;              // disable all interrupts
 			_TC->INTENSET.bit.OVF = 1;          // enable overfollow
 			// Skip: while (_TC->STATUS.bit.SYNCBUSY == 1); // sync
@@ -174,7 +189,6 @@
 	 * Note: This is device-dependant
 	 */
 	void uTimerLib::_loadRemaining() {
-		_TC->COUNT.reg = 0;              // Reset to 0
 		_TC->CC[0].reg = _remaining;
 		_TC->INTENSET.reg = 0;              // disable all interrupts
 		_TC->INTENSET.bit.MC0 = 1;          // enable compare match to CC0
@@ -217,28 +231,22 @@
 			if (_type == UTIMERLIB_TYPE_TIMEOUT) {
 				clearTimer();
 			} else if (_type == UTIMERLIB_TYPE_INTERVAL) {
-				if (__overflows == 0) {
-					_remaining = __remaining;
-					_loadRemaining();
-					_remaining = 0;
-				} else {
+				if (__overflows != 0) {
 					_overflows = __overflows;
 					_remaining = __remaining;
 
-					_TC->COUNT.reg = 0;              // Reset to 0
 					_TC->INTENSET.reg = 0;              // disable all interrupts
 					_TC->INTENSET.bit.OVF = 0;          // enable overfollow
 					_TC->INTENSET.bit.MC0 = 1;          // disable compare match to CC0
-					_TC->CC[0].reg = 65535;
+					_TC->CC[0].reg = UINT16_MAX;
 				}
 			}
 			_cb();
 		} else if (_overflows > 0) { // Reload for SAMD21
-			_TC->COUNT.reg = 0;              // Reset to 0
 			_TC->INTENSET.reg = 0;              // disable all interrupts
 			_TC->INTENSET.bit.OVF = 0;          // enable overfollow
 			_TC->INTENSET.bit.MC0 = 1;          // disable compare match to CC0
-			_TC->CC[0].reg = 65535;
+			_TC->CC[0].reg = UINT16_MAX;
 		}
 	}