Merge pull request arduino#52 from Kees-van-der-Oord/main

Bugfix: `micros()` returns smaller number when timer wraps

Author: aentinger

Diff for: .gitignore

@@ -3,4 +3,6 @@ cores/arduino/mydebug.cpp
 libraries/Storage/.development
 cores/arduino/mydebug.cpp.donotuse
 .DS_Store
-.DS_Store?
+.DS_Store?
+/.vs
+/.gitignore

Diff for: cores/arduino/time.cpp

@@ -2,8 +2,7 @@
 #include "IRQManager.h"
 #include "FspTimer.h"
 
-volatile unsigned long agt_time_ms = 0;
-uint32_t _freq_hz = 0;
+// this file implements the following public funcions: delay, delayMicroseconds, yield, millis, micros
 
 __attribute__((weak)) void delay(uint32_t ms) {
 	R_BSP_SoftwareDelay(ms, BSP_DELAY_UNITS_MILLISECONDS);
@@ -16,21 +15,31 @@ void delayMicroseconds(unsigned int us) {
 __attribute__((weak)) void yield() {
 }
 
-static FspTimer main_timer;
+static FspTimer   agt_timer;
+volatile uint32_t agt_time_ms = 0;
 
-static uint32_t _top_counter;
-
-static void timer_micros_callback(timer_callback_args_t __attribute((unused)) *p_args) {
-	agt_time_ms += 1; //1ms
+static void timer_micros_callback(timer_callback_args_t __attribute((unused))* p_args) {
+	agt_time_ms += 1;
 }
 
 void startAgt() {
-	main_timer.begin(TIMER_MODE_PERIODIC, AGT_TIMER, 0, 2000.0f, 0.5f, timer_micros_callback);
-	IRQManager::getInstance().addPeripheral(IRQ_AGT,(void*)main_timer.get_cfg());
-	main_timer.open();
-	_top_counter = main_timer.get_counter();
-	main_timer.start();
-	_freq_hz = main_timer.get_freq_hz();
+	// configure AGT timer 0 to generate an underflow interrupt every 1 ms
+	// a clock divider 8 works for both the Uno R4 and Portenta C33 because number of clock ticks 
+	// in 1 ms (period) is an integer number and below the 16-bit counter limit
+	// on the Uno R4 the AGT clock is 24 MHz / 8 -> 3000 ticks per ms
+	// on the Portenta C33 the AGT clock is 50 Mhz / 8 -> 6250 ticks per ms
+	const uint32_t clock_freq_Hz = R_FSP_SystemClockHzGet(FSP_PRIV_CLOCK_PCLKB);
+	const uint32_t period = clock_freq_Hz / ((1 << TIMER_SOURCE_DIV_8) * 1000UL);
+	agt_timer.begin(/* mode */ TIMER_MODE_PERIODIC,
+                  /* type */ AGT_TIMER,
+                  /* channel */ 0,
+                  period,
+                  /* pulse */ 1,
+                  TIMER_SOURCE_DIV_8,
+                  timer_micros_callback);;
+	agt_timer.setup_overflow_irq(8);
+	agt_timer.open();
+	agt_timer.start(); // bug in R4 1.0.2: calling start() is not necessary: open() starts the counter already !?
 }
 
 unsigned long millis()
@@ -43,10 +52,18 @@ unsigned long millis()
 }
 
 unsigned long micros() {
-
-	// Convert time to us
-	NVIC_DisableIRQ(main_timer.get_cfg()->cycle_end_irq);
-	uint32_t time_us = ((main_timer.get_period_raw() - main_timer.get_counter()) * 1000 / main_timer.get_period_raw()) +  (agt_time_ms * 1000);
-	NVIC_EnableIRQ(main_timer.get_cfg()->cycle_end_irq);
-	return time_us;
+	// Return time in us
+	const timer_cfg_t* cfg = agt_timer.get_cfg();
+	NVIC_DisableIRQ(cfg->cycle_end_irq);
+	uint32_t ms = agt_time_ms;
+	// read from the R_AGT0 registers directly for performance reasons
+	uint32_t const down_counts = R_AGT0->AGT; // get the counter value
+	if (R_AGT0->AGTCR_b.TUNDF && (down_counts > (cfg->period_counts / 2))) {
+		// if the TUNDF (underflow) bit is set, the counter wrapped around 
+		// just before down_counts was read and agt_time_ms was not yet updated
+		++ms;
+	}
+	NVIC_EnableIRQ(cfg->cycle_end_irq);
+	uint32_t const up_counts = (cfg->period_counts - 1) - down_counts;
+	return  (ms * 1000) + ((up_counts * 1000) / cfg->period_counts);
 }