Interrupt interval 2X requested interval
wcwuttke opened this issue · 9 comments
wcwuttke commented
Arduino IDE version 1.8.13
Adruino WiFI Rev 2
OS: Win 10
Context:
Actual interrupt delay is 2 times the programmed value. e.g., programmed value = 10 ms., actual value = 20 ms.
Steps to reproduce:
- Compile and run the Argument_None example with: #define TIMER1_INTERVAL_MS 11L, adding pin A0 to the
toggle1 code to observe the output on an oscilloscope connected to pin A0. - Observe that the waveform toggles at twice the programmed value (22 ms).
Works the same with any clock selected.
Am I doing something wrong?
/****************************************************************************************************************************
Argument_None.ino
For Arduino megaAVR ATMEGA4809-based boards (UNO WiFi Rev2, NANO_EVERY, etc. )
Written by Khoi Hoang
Built by Khoi Hoang https://github.com/khoih-prog/megaAVR_TimerInterrupt
Licensed under MIT license
Now with we can use these new 16 ISR-based timers, while consuming only 1 hwarware Timer.
Their independently-selected, maximum interval is practically unlimited (limited only by unsigned long miliseconds)
The accuracy is nearly perfect compared to software timers. The most important feature is they're ISR-based timers
Therefore, their executions are not blocked by bad-behaving functions / tasks.
This important feature is absolutely necessary for mission-critical tasks.
Version: 1.3.0
Version Modified By Date Comments
------- ----------- ---------- -----------
1.0.0 K.Hoang 01/04/2021 Initial coding to support Arduino megaAVR ATmega4809-based boards (UNO WiFi Rev2, etc.)
1.1.0 K.Hoang 14/04/2021 Fix bug. Don't use v1.0.0
1.2.0 K.Hoang 17/04/2021 Selectable TCB Clock 16MHz, 8MHz or 250KHz depending on necessary accuracy
1.3.0 K.Hoang 17/04/2021 Fix TCB Clock bug. Don't use v1.2.0
*****************************************************************************************************************************/
// These define's must be placed at the beginning before #include "megaAVR_TimerInterrupt.h"
// _TIMERINTERRUPT_LOGLEVEL_ from 0 to 4
// Don't define _TIMERINTERRUPT_LOGLEVEL_ > 0. Only for special ISR debugging only. Can hang the system.
#define TIMER_INTERRUPT_DEBUG 0
#define _TIMERINTERRUPT_LOGLEVEL_ 0
// Select USING_16MHZ == true for 16MHz to Timer TCBx => shorter timer, but better accuracy
// Select USING_8MHZ == true for 8MHz to Timer TCBx => shorter timer, but better accuracy
// Select USING_250KHZ == true for 250KHz to Timer TCBx => shorter timer, but better accuracy
// Not select for default 250KHz to Timer TCBx => longer timer, but worse accuracy
#define USING_16MHZ false
#define USING_8MHZ false
#define USING_250KHZ true
#define USE_TIMER_0 false
#define USE_TIMER_1 true
#define USE_TIMER_2 false
#define USE_TIMER_3 false
#include "megaAVR_TimerInterrupt.h"
#define TIMER1_INTERVAL_MS 11L
#ifndef LED_BUILTIN
#define LED_BUILTIN 13
#endif
void TimerHandler1(void)
{
static bool toggle1 = false;
static bool started = false;
if (!started)
{
started = true;
pinMode(LED_BUILTIN, OUTPUT);
pinMode(A0, OUTPUT);
}
//timer interrupt toggles pin LED_BUILTIN
digitalWrite(LED_BUILTIN, toggle1);
digitalWrite(A0, toggle1);
toggle1 = !toggle1;
}
#if USE_TIMER_2
#define TIMER2_INTERVAL_MS 2
void TimerHandler2(void)
{
static bool toggle2 = false;
static bool started = false;
if (!started)
{
started = true;
pinMode(A0, OUTPUT);
}
//timer interrupt toggles outputPin
digitalWrite(A0, toggle2);
toggle2 = !toggle2;
}
#endif
void setup()
{
Serial.begin(115200);
while (!Serial);
Serial.print(F("\nStarting Argument_None on "));
Serial.println(BOARD_NAME);
Serial.println(MEGA_AVR_TIMER_INTERRUPT_VERSION);
Serial.print(F("CPU Frequency = ")); Serial.print(F_CPU / 1000000); Serial.println(F(" MHz"));
Serial.print(F("TCB Clock Frequency = "));
#if USING_16MHZ
Serial.println(F("16MHz for highest accuracy"));
#elif USING_8MHZ
Serial.println(F("8MHz for very high accuracy"));
#else
Serial.println(F("250KHz for lower accuracy but longer time"));
#endif
// Select Timer 1-2 for UNO, 0-5 for MEGA
// Timer 2 is 8-bit timer, only for higher frequency
ITimer1.init();
// Using ATmega328 used in UNO => 16MHz CPU clock ,
// For 16-bit timer 1, 3, 4 and 5, set frequency from 0.2385 to some KHz
// For 8-bit timer 2 (prescaler up to 1024, set frequency from 61.5Hz to some KHz
if (ITimer1.attachInterruptInterval(TIMER1_INTERVAL_MS, TimerHandler1))
{
Serial.print(F("Starting ITimer1 OK, millis() = ")); Serial.println(millis());
}
else
Serial.println(F("Can't set ITimer1. Select another freq. or timer"));
#if USE_TIMER_2
// Select Timer 1-2 for UNO, 0-5 for MEGA
// Timer 2 is 8-bit timer, only for higher frequency
ITimer2.init();
if (ITimer2.attachInterruptInterval(TIMER2_INTERVAL_MS, TimerHandler2))
{
Serial.print(F("Starting ITimer2 OK, millis() = ")); Serial.println(millis());
}
else
Serial.println(F("Can't set ITimer2. Select another freq. or timer"));
#endif
}
void loop()
{
}
khoih-prog commented
Hi @wcwuttke
Thanks for your interests in the library.
- I think you have to use 16MHz clock to Timers for better accuracy
// Select USING_16MHZ == true for 16MHz to Timer TCBx => shorter timer, but better accuracy
// Select USING_8MHZ == true for 8MHz to Timer TCBx => shorter timer, but better accuracy
// Select USING_250KHZ == true for 250KHz to Timer TCBx => shorter timer, but better accuracy
// Not select for default 250KHz to Timer TCBx => longer timer, but worse accuracy
#define USING_16MHZ true
#define USING_8MHZ false
#define USING_250KHZ false
also megaAVR is a very slow MCU, doing to many things within 10ms, such as
//timer interrupt toggles pin LED_BUILTIN
digitalWrite(LED_BUILTIN, toggle1);
digitalWrite(A0, toggle1);
possibly distorts its timings.
- Try this example ISR_16_Timers_Array_Complex.
The best way to know the timings is correct is to use a counter inside the ISR, then print it out using a timing loop outside ISR, using millis().
For example, you can see the timing is very accurate here
Starting ISR_16_Timers_Array_Complex on megaAVR Nano Every
megaAVR_TimerInterrupt v1.3.0
CPU Frequency = 16 MHz
TCB Clock Frequency = 16MHz for highest accuracy
[TISR] TCB 1
[TISR] ==================
[TISR] Init, Timer = 1
[TISR] CTRLB = 0
[TISR] CCMP = 65535
[TISR] INTCTRL = 0
[TISR] CTRLA = 1
[TISR] ==================
[TISR] Frequency = 200.00 , CLK_TCB_FREQ = 16000000
[TISR] setFrequency: _CCMPValueRemaining = 80000
[TISR] ==================
[TISR] set_CCMP, Timer = 1
[TISR] CTRLB = 0
[TISR] CCMP = 65535
[TISR] INTCTRL = 1
[TISR] CTRLA = 1
Starting ITimer1 OK, millis() = 13
SimpleTimer : 2, ms : 10013, Dms : 10013
Timer : 0, programmed : 5000, actual : 5015
Timer : 1, programmed : 10000, actual : 0
Timer : 2, programmed : 15000, actual : 0
Timer : 3, programmed : 20000, actual : 0
Timer : 4, programmed : 25000, actual : 0
Timer : 5, programmed : 30000, actual : 0
Timer : 6, programmed : 35000, actual : 0
Timer : 7, programmed : 40000, actual : 0
Timer : 8, programmed : 45000, actual : 0
Timer : 9, programmed : 50000, actual : 0
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 20072, Dms : 10059
Timer : 0, programmed : 5000, actual : 4998
Timer : 1, programmed : 10000, actual : 9995
Timer : 2, programmed : 15000, actual : 15017
Timer : 3, programmed : 20000, actual : 20015
Timer : 4, programmed : 25000, actual : 0
Timer : 5, programmed : 30000, actual : 0
Timer : 6, programmed : 35000, actual : 0
Timer : 7, programmed : 40000, actual : 0
Timer : 8, programmed : 45000, actual : 0
Timer : 9, programmed : 50000, actual : 0
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 30131, Dms : 10059
Timer : 0, programmed : 5000, actual : 4997
Timer : 1, programmed : 10000, actual : 10002
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 20015
Timer : 4, programmed : 25000, actual : 25020
Timer : 5, programmed : 30000, actual : 30017
Timer : 6, programmed : 35000, actual : 0
Timer : 7, programmed : 40000, actual : 0
Timer : 8, programmed : 45000, actual : 0
Timer : 9, programmed : 50000, actual : 0
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 40192, Dms : 10061
Timer : 0, programmed : 5000, actual : 5005
Timer : 1, programmed : 10000, actual : 10002
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 20004
Timer : 4, programmed : 25000, actual : 25020
Timer : 5, programmed : 30000, actual : 30017
Timer : 6, programmed : 35000, actual : 35014
Timer : 7, programmed : 40000, actual : 40019
Timer : 8, programmed : 45000, actual : 0
Timer : 9, programmed : 50000, actual : 0
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 50252, Dms : 10060
Timer : 0, programmed : 5000, actual : 4997
Timer : 1, programmed : 10000, actual : 9995
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 20004
Timer : 4, programmed : 25000, actual : 24994
Timer : 5, programmed : 30000, actual : 30017
Timer : 6, programmed : 35000, actual : 35014
Timer : 7, programmed : 40000, actual : 40019
Timer : 8, programmed : 45000, actual : 45017
Timer : 9, programmed : 50000, actual : 50014
Timer : 10, programmed : 55000, actual : 0
Timer : 11, programmed : 60000, actual : 0
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 60314, Dms : 10062
Timer : 0, programmed : 5000, actual : 4997
Timer : 1, programmed : 10000, actual : 10002
Timer : 2, programmed : 15000, actual : 14999
Timer : 3, programmed : 20000, actual : 19997
Timer : 4, programmed : 25000, actual : 24994
Timer : 5, programmed : 30000, actual : 29999
Timer : 6, programmed : 35000, actual : 35014
Timer : 7, programmed : 40000, actual : 40019
Timer : 8, programmed : 45000, actual : 45017
Timer : 9, programmed : 50000, actual : 50014
Timer : 10, programmed : 55000, actual : 55019
Timer : 11, programmed : 60000, actual : 60016
Timer : 12, programmed : 65000, actual : 0
Timer : 13, programmed : 70000, actual : 0
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 70376, Dms : 10062
Timer : 0, programmed : 5000, actual : 5006
Timer : 1, programmed : 10000, actual : 10003
Timer : 2, programmed : 15000, actual : 14999
Timer : 3, programmed : 20000, actual : 19997
Timer : 4, programmed : 25000, actual : 24994
Timer : 5, programmed : 30000, actual : 29999
Timer : 6, programmed : 35000, actual : 35005
Timer : 7, programmed : 40000, actual : 40019
Timer : 8, programmed : 45000, actual : 45017
Timer : 9, programmed : 50000, actual : 50014
Timer : 10, programmed : 55000, actual : 55019
Timer : 11, programmed : 60000, actual : 60016
Timer : 12, programmed : 65000, actual : 65013
Timer : 13, programmed : 70000, actual : 70019
Timer : 14, programmed : 75000, actual : 0
Timer : 15, programmed : 80000, actual : 0
SimpleTimer : 2, ms : 80439, Dms : 10063
Timer : 0, programmed : 5000, actual : 4997
Timer : 1, programmed : 10000, actual : 9994
Timer : 2, programmed : 15000, actual : 15000
Timer : 3, programmed : 20000, actual : 19997
Timer : 4, programmed : 25000, actual : 25002
Timer : 5, programmed : 30000, actual : 29999
Timer : 6, programmed : 35000, actual : 35005
Timer : 7, programmed : 40000, actual : 39994
Timer : 8, programmed : 45000, actual : 45017
Timer : 9, programmed : 50000, actual : 50014
Timer : 10, programmed : 55000, actual : 55019
Timer : 11, programmed : 60000, actual : 60016
Timer : 12, programmed : 65000, actual : 65013
Timer : 13, programmed : 70000, actual : 70019
Timer : 14, programmed : 75000, actual : 75016
Timer : 15, programmed : 80000, actual : 80013
Good Luck,
wcwuttke commented
Hello,
I need a 1 millisecond timer. That can only be done with the 250 KHz clock.
According to the formula, the correct value gets stored in TCB1_CCMP
(250) for a 1 ms timer. However, the timer interval is 2 ms. I made a workaround
by changing TCB1_CCMP in my code. Now I have interrupts occurring at
precise 1 ms intervals (as measured with my oscilloscope). It behaves as if the
250 KHz clock has been divided by two somewhere.
Bill Wuttke
khoih-prog commented
Good to know it's OK for you.
It behaves as if the 250 KHz clock has been divided by two somewhere.
I actually haven't tested with 250KHz. Possibly a bug somewhere in this library, or the core???
I'll spend some time to investigate later whenever I have time. I'd appreciate it you could help here to locate the issue.
Regards,
wcwuttke commented
Hello Khoi,
I'll be investigating further tomorrow. It's been a long time since I've played around with registers, etc.,
and then it was on 6800 & Z80s. Things have changed alot since then. Anyhow, I'll try to do
some register manipulation to get a basic timer going so I can do a comparison. I'll let
you know what I find.
Regards,
Bil Wuttke
On Sunday, September 5, 2021, 07:09:51 PM PDT, Khoi Hoang ***@***.***> wrote:
Good to know it's OK for you.
It behaves as if the 250 KHz clock has been divided by two somewhere.
I actually haven't tested with 250KHz. Possibly a bug somewhere in this library, or the core???
I'll spend some time to investigate later whenever I have time. I'd appreciate it you could help here to locate the issue.
Regards,
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wcwuttke commented
Hello Khoi,
I wrote two test sketches today, one for TCA, and one for TCB, using direct register manipulation.
Both work correctly, delivering 1 millisecond interrupts using sys_clk/64. Both are attached.
(Although the TCB timing is a little "glitchy" on the oscilloscope.) The TCB code probably
has an error or two.
Regards,
Bill Wuttke
//**************************************************************************************************
//**************************************************************************************************
// TCA Timer Test Sketch. 1 millisecond timer.
// modified from Microchip TB3217 example 7-1
#define PERIOD_EXAMPLE_VALUE (249) /* 1 millisecond using sys_clk/64 */
void TCA0_init(void)
{
/* enable overflow interrupt */
TCA0.SINGLE.INTCTRL = TCA_SINGLE_OVF_bm;
/* set Normal mode */
TCA0.SINGLE.CTRLB = TCA_SINGLE_WGMODE_NORMAL_gc;
/* disable event counting */
TCA0.SINGLE.EVCTRL &= ~(TCA_SINGLE_CNTEI_bm);
/* set the period */
TCA0.SINGLE.PER = PERIOD_EXAMPLE_VALUE;
TCA0.SINGLE.CTRLA = TCA_SINGLE_CLKSEL_DIV64_gc /* set clock source (sys_clk/64) */
| TCA_SINGLE_ENABLE_bm; /* start timer */
}
void PORT_init(void)
{
/* set pin 0 of PORT A as output */
pinMode(A0, OUTPUT);
}
ISR(TCA0_OVF_vect)
{
static bool toggle1 = false;
/* Toggle PIN 0 of PORT A */
digitalWrite(A0, toggle1);
toggle1 = !toggle1;
/* The interrupt flag has to be cleared manually */
TCA0.SINGLE.INTFLAGS = TCA_SINGLE_OVF_bm;
}
void setup() {
PORT_init();
TCA0_init();
/* enable global interrupts */
sei();
}
void loop() {
}
//**************************************************************************************************
//**************************************************************************************************
// TCB Timer Test Sketch. 1 millisecond timer.
#define PERIOD_EXAMPLE_VALUE (250) /* 1 millisecond using sys_clk/64 */
void CLOCK_init (void)
{
/* Enable writing to protected register */
CPU_CCP = CCP_IOREG_gc;
/* Enable Prescaler and set Prescaler Division to 64 */
CLKCTRL.MCLKCTRLB = CLKCTRL_PDIV_64X_gc | CLKCTRL_PEN_bm;
/* Enable writing to protected register */
CPU_CCP = CCP_IOREG_gc;
/* Select OSC20M */
CLKCTRL.MCLKCTRLA = CLKCTRL_CLKSEL_OSC20M_gc;
/* Wait for system oscillator changing to finish */
while (CLKCTRL.MCLKSTATUS & CLKCTRL_SOSC_bm)
{
;
}
}
void TCB1_init(void)
{
/* Load the Compare or Capture register with the timeout value*/
TCB1.CCMPL = PERIOD_EXAMPLE_VALUE;
TCB1.CCMPH = 0;
/* Enable TCB and set CLK_PER divider to 1 (No Prescaling) */
TCB1.CTRLA = TCB_CLKSEL_CLKDIV1_gc | TCB_ENABLE_bm;
/* Configure TCB in Periodic Timeout mode */
TCB1.CTRLB = TCB_CCMPEN_bm;
/* Enable Capture or Timeout interrupt */
TCB1.INTCTRL = TCB_CAPT_bm;
}
void PORT_init (void)
{
/* set pin 0 of PORT A as output */
pinMode(A0, OUTPUT);
}
ISR(TCB1_INT_vect)
{
static bool toggle1 = false;
/* Toggle PIN 0 of PORT A */
digitalWrite(A0, toggle1);
toggle1 = !toggle1;
/* The interrupt flag has to be cleared manually */
TCB1.INTFLAGS = TCB_CAPT_bm; /* Clear the interrupt flag */
}
void setup() {
CLOCK_init();
PORT_init();
TCB1_init();
sei();
}
void loop() {
}
On Sunday, September 5, 2021, 07:09:51 PM PDT, Khoi Hoang ***@***.***> wrote:
Good to know it's OK for you.
It behaves as if the 250 KHz clock has been divided by two somewhere.
I actually haven't tested with 250KHz. Possibly a bug somewhere in this library, or the core???
I'll spend some time to investigate later whenever I have time. I'd appreciate it you could help here to locate the issue.
Regards,
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khoih-prog commented
Thanks Bill,
The TCB code probably has an error or two.
Do you mean error in the library? I believe so.. Could you please help locate and make a PR ?
If not possible due to time constraint, it's OK and I understand and will fix it later.
I'm reopening the issue now
Best Regards,
Khoi
wcwuttke commented
Hello Khoi,
I've been trying to locate the problem - it looks like you set the timer registers correctly.
It looks like you are not using the interrupt directly, but do something with counts - that's
where I get lost.
I am totally unfamiliar with the workings of Github, except that it stores one of my projects.
Therefore, I'll leave the PR, etc, for you.
My immediate problem (need for 1 ms timer) has been solved by using a few lines of code to
set the timer registers.
Best Regards,
Bill Wuttke
On Monday, September 6, 2021, 01:51:10 PM PDT, Khoi Hoang ***@***.***> wrote:
Thanks Bill,
The TCB code probably has an error or two.
Do you mean error in the library? I believe so.. Could you please help locate and make a PR ?
If not possible due to time constraint, it's OK and I understand and will fix it later.
I'm reopening the issue now
Best Regards,
Khoi
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khoih-prog commented
Hi Bill,
Thanks. I'll spend some time later to investigate, locate and solve this issue.
Regards,
khoih-prog commented
Hi @wcwuttke
I'm sorry to wait too long to fix the bug, which is delicate and hard-to-find and happened only to high frequencies (around >245Hz). The bug has just been fixed by the new megaAVR_TimerInterrupt releases v1.4.0
Your contribution is noted in Contributions and Thanks
Regards,
Release v1.4.0
- Fix TCB Clock bug in high frequencies. Check Interrupt interval 2X requested interval #1
- Add example to demo High Frequency
- Delete Blynk-related examples
- Add changelog.md