I am new to Arduino programming and trying to use the arduino uno as a high resolution timer. I would like to be able to count clock cycles at the full 16MHz rate between two rising edge interrupts. I have some code that is functional using the micros() function which has 4 microsecond resolution, and I need better than that. Here is an example code where I am trying to use micros() for the timing:
volatile int k = 0;
volatile float t1 = 0;
volatile float t2 = 0;
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
attachInterrupt(digitalPinToInterrupt(2), ISR1, RISING);
attachInterrupt(digitalPinToInterrupt(3), ISR2, RISING);
}
void ISR2()
{
k = 1;
t1 = micros();
Serial.println(1);
}
void ISR1()
{
k = 2;
t2 = micros();
Serial.println(2);
}
void loop()
{
if (t1 != 0 && t2 != 0) {
if (t2 - t1 < 0) {
t1 = 0;
t2 = 0;
}
else {
Serial.print("tdelta ");
Serial.print(t2 - t1);
t1 = 0;
t2 = 0;
Serial.println(0);
}
}
}
I realize that my micros timing is probably getting a bit offset by the interrupts, which may be an issue.
Can anyone point me in the right direction?
I think I want to use timer1 since it is 16 bit and my events should be fast enough to be completed before any overflow occurs. I am hoping to find a simple way to set up tcnt1 to be 0 with the first interrupt and then count tcnt1 clock cycles until the second interrupt. I don't really even know how to read the values from tcnt1 though, so I have a ways to go.
I have searched for examples, but haven't really found one that seems appropriate. Everything seems to be geared towards timer interrupts which I don't think is quite what I'm after.
I am probably lacking a lot of needed understanding to use this tcnt1 counter, but any help to point me in the right direction would be greatly appreciated!
Thanks
You can try to work with timer registers directly. Look at manual for CPU which is used on your particular board. For mega it is ATmega2560-16AU. Timer register's name is TCNT1. You can store its value:
int t1;// declare global variable somewhere
t1 = TCNT1; //save timer value in ISRx interrupts
Be sure to setup prescaler value TCCR1B.CSn and handle timer overflow interrupt, else you will lose time data: ISR(TIMER1_OVF_vect)
As you can read here here precision of <1 uS can be reached.
More info of how to work directly with CPU timers registers.
Related
I am working on a school project for which I rotate a servo after a cable disconnects and a specific delay is over. This is my current code. We are using an Arduino Uno powered from the USB port
#include <Servo.h>
int reader=4;
int servo1Pin=8;
Servo servo1;
int value;
int pos=10;
int wacht=5000;
void setup() {
pinMode(reader, INPUT);
servo1.attach(servo1Pin);
}
void loop() {
value = digitalRead(reader);
servo1.write(pos);
if (value == LOW) {
delay(wacht);
pos=180;
}
else {
pos=10;
}
}
wacht is the specific delay. When we disconnected pin 4 to break that circuit we don't have a consistent time between the interruption of the power flow and the opening of the servo. It seems to vary from anywhere between 5 to 40 seconds of delay after triggering. Does anyone have any ideas to solve this issue?
try change
pinMode(reader, INPUT);
to
pinMode(reader, INPUT_PULLUP);
And for clarification delay don't use timer.
The order of your instructions seem strange. the usual order is:
Read
Decide
Act
Also, you may want to avoid sending useless instructions to the servo. For example, when you know the servo is already in the correct position. You should not rely on eternal code to do the right thing. In other terms, you have no idea how long servo1.write() takes to execute.
Which would give for your loop()
void loop()
{
if (digitalRead(reader) == LOW)
{
if (pos != 180)
{
delay(wacht); // delay() is only called once, when circuit breaks.
// this guarantees immediate response when circuit
∕/ closes again.
pos = 180;
servo1.write(pos);
}
}
else if (pos != 10)
{
pos = 10;
servo1.write(pos);
}
}
Also, have a look and implement Peter Plesník's answer. This will probably solve some of your problems. You input will definitely still have a random lag of up to 5 seconds when closing the circuit, though.
I am working with an hall sensor for counting the RPM of my wheel. I am using following sensor :
My code as follows :
int hall_pin = 3; // digital pin
float hall_threshold = 5.0;
float count = 0;
void setup() {
pinMode(hall_pin,INPUT);// put your setup code here, to run once:
Serial.begin(9600);
attachInterrupt(digitalPinToInterrupt(hall_pin),hall_ISR,RISING);
}
void loop() {
count = 0.0;
float start = micros();
while(1){
if(count >= hall_threshold){
break;
}
}
float end_time = micros();
float time_passed = (end_time - start)/1000000.0; // in seconds
float rpm = (count/time_passed)*60.0;
Serial.println(rpm);
delay(10000);
}
void hall_ISR()
{
count+=1.0;
}
I am using digital pin 3 to read from sensor and count the number of times it detects magnetic field using interrupt. Since the sensor outputs 1 on detecting, I have used a RISING interrupt. Once the count is greater than 5 then the control comes out of the infinite loop and calculates the RPM. The problem is this interrupt is getting triggered multiple times. I have tried using detachInterrupt(hall_pin) but it is not working. I also tried to decrease the sensitivity of hall sensor using the trimmer provided.
I am sure the problem is not with the sensor, it is with the interrupt, I guess. Where am I going wrong?
Any help is very much appreciated!
Thank you.
I am using a Remote Control from FlySky. For my robotics project, I want to read PWM from the receiver on an Arduino. I came across 2 options:
pulseIn() arduino function
ISR(PCINTx_vect) (interrupt)
I cant use the first option of pulseIn() because I want my robot to continue with the operation if receiver signal are not coming (Tx not available etc.) So I used ISR.
Most reliable source : Mr. Brookings channel on YouTube.
Here is what I did (Only the required part for 1 axis):
// [R] where R is defined as 0 => [R] == [0]
volatile long CH[4]; //4 pwms to read so array of 4
float IN[3]={0,0,0}; // throttle is directly written
unsigned long timer[4],curr_time;
byte last[4];
void setup(){
PCICR |= (1 << PCIE0);
PCMSK0 |= (1 << PCINT0);
PCMSK0 |= (1 << PCINT1);
PCMSK0 |= (1 << PCINT2);
PCMSK0 |= (1 << PCINT3);
/* There is some more code here */
Serial.begin(115200);
}
void loop(){
/* There is some more code here */
IN[R] = ((CH[ROLL] - (1500 + R_TRIM))/11.0); // eg.: (1200 - (1500 + 8))/11.0 = -28 (interpreted as setpoint of -28° by the robot)
Serial.println(IN[R]);
}
ISR(PCINT0_vect){
curr_time = micros();
//channel 1 roll
if(PINB & B00000001){
if(last[ROLL] == 0){
last[ROLL] = 1;
timer[ROLL] = curr_time;
}
}
else if(last[ROLL] == 1){
last[ROLL] = 0;
CH[ROLL] = ((curr_time - timer[ROLL]));
}
}
I can read the PWM actually, but the robot keeps showing random twitches in its control at a given set point. I managed to trace the reason and found out that the PWM is insanely ridden by noise. Its not stable like it should be - steady. I have a MATLAB plot I used for analysis:
Signal (IN[R]):
Close up (when Tx stick was in the middle w/o movement) :
There are such spikes coming which is adding up to the control signal eventually making my robot to twitch. I tried some filtering techniques like 'moving average' and '1st and 2nd order exponential filters'. Also checked if it was due to power supplied to it - tried putting a capacitor or an iron core to the power lines but in vain. I can figure out how to remove them as their some constrains :
platform is Arduino Uno (slower in heavy computation)
Control loop shall not go below 100Hz (Currently its at 108Hz exponential filters on 4 axes took it to
~85Hz)
I would appreciate some guidance!
There's no way of telling from this if the input is noisy, or if your code is reading the PWM wrong, of if something else is going on, like external noise on the line, the Arduino's clock jitter, or other interrupts taking time. Also note that micros() on an Arduino Uno only has a resolution of 4µs, not 1µs.
You should check the input for jitter and noise, and try fast code that isn't influenced by other interrupts.
A fairly simple and fast way of getting the PWM pulse width is something like this, preferably without using anything else that uses interrupts:
volatile int pwmPulseWidth = 0;
volatile unsigned long int previousTime = 0;
void setup() {
attachInterrupt(0, rising, RISING);
}
void loop() {
// pwmPulseWidth is available here.
}
void rising() {
attachInterrupt(0, falling, FALLING);
previousTime = micros();
}
void falling() {
attachInterrupt(0, rising, RISING);
pwmPulseWidth = micros() - previousTime;
}
Untested, but it should give you an idea. This will return the width of the PWM pulse.
There are other ways of doing this, of course, like using a timer in capture mode.
Knowing the PWM frequency and the width of the PWM pulse is enough to reconstruct the PWM signal, should you want to.
I am using an Arduino Uno, connected to a USB shield, a RFID shield(adafruit PN532), an LCD, EEPROM(24AA256) and a RTC module(DS1307). I will not post my code here because it is too large and it is separated in multiple files.
In my program, I realize that if my programs enters a certain functions, after entering function after function, if I use a delay() at the end of the function I am currently in, the arduino resets. An example of what I mean is below.
void a() { b(); }
void b() { c(); }
void c() { d(); }
void d()
{
lcd_string("Testing", 0x80);
delay(2000); <---- Arduino resets at the delay here
}
At first, I thought it was because my dynamic memory was at 80%, and when I compiled, they said the Arduino might have some stability issues. So I modified my code such that my dynamic memory is now 57%. Problem still exist.
I thought maybe the delay() function has some overflow or something, so I tried replacing the delay with the following code.
unsigned long timing;
timing = millis();
timing += 2000;
while(millis() < timing);
The Arduino still resets.
Next, I thought maybe because my arduino is connected to my PC, some serial pin might have been causing the reset, so I used an external Power to power up the arduino and disconnected the USB. The arduino still resets.
Next, I thought maybe Timer1 might have been crashing with the delay() function, although the delay function uses Timer0 so I disabled my Timer1 . The arduino still resets.
Is there any other possibilities that I am missing out? My program storage space is at 69% which I believe shouldn't be an issue.
Edit
Here is my code for Timer1 ISR
ISR(TIMER1_OVF_vect)
{
TCCR1A = 0;
TCCR1B = 0;
TCNT1 = 0;
OCR1A = 34286;// = (16*10^6) / (1*1024) - 1 (must be <65536)
TCCR1B |= (1 << CS12);
// enable timer compare interrupt
TIMSK1 |= (1 << TOIE1);
triggered = 1;
}
Any other interrupt of flags used are in the library header files.
I am using the following external libraries
USB Host shield library 2.0
Adafruit PN532 master
A little sample to come close to RAM corruption ...
#define MEM_PER_LEVEL 50
#define TRY_TO_SURVIVE 10
void KillMe(int level) {
byte dummy[MEM_PER_LEVEL];
for ( byte i = 0; i < MEM_PER_LEVEL; i++)
dummy[i]= i;
Serial.println(level);
delay(1000); // not sure why this would hurt more than others
if (level < TRY_TO_SURVIVE) KillMe(level+1);
for ( byte i = 0; i < MEM_PER_LEVEL; i++) {
if (dummy[i] != i) {
Serial.println(F("corruption happened"));
while(1) {} // HALT
}
}
if (level == 0)
Serial.println(F("survived"));
}
void setup() {
Serial.begin(9600);
KillMe(0);
}
void loop() { }
I had the same problem - wherever I put a delay in my setup function the Arduino would restart.
For me, the problem was an instance of SoftwareSerial with invalid pin numbers.
SoftwareSerial mySerial(30, 31);
Anyone else landing on this question should check their pin numbers are appropriate for the board they're targeting. Not sure why the crash only happens if a delay is called, would be interested if anyone has insight into this!
It is possible to serial print how milliseconds every output high. Let say i write an code analogRead. If analogread bigger than 600, then digitalwrite 13, high. If output pin 13 high, then capture how millisecond until the pin 13 goto low.
I try millis() but it cannot reset back to zero... It there anyway to reset millis() to zero?
You need a variable to keep track of your millis() count between events, kind of like a stop watch: you need to remember you started counting, so you can measure the difference when you stop.
Here's a quick sketch to illustrate the idea. Code isn't tested on an Arduino, but you should be able to understand the concept from the comments:
long lastTime;
int ledState = 0;
void setup() {
Serial.begin(115200);
pinMode(13,OUTPUT);
}
void loop() {
int analogValue = analogRead(0);
int newLedState = (analogValue > 600);//need to check, hoping boolean will evaluat to 1 when true
if(ledState == 0 && newLedState == 1){//if the led was of, but will be turned on, start the stop watch
lastTime = millis();//store the current time
ledState = newLedState;
}
if(ledState == 1 && newLedState == 0){//if the led was on, but will be turned off, get the difference between the last time we started counting time
long difference = millis() - lastTime; //get the current time, but subtract the last stored time
ledState = newLedState;
Serial.println(difference);
}
digitalWrite(13,ledState);
}
Okay so I think I understand what you want here. You want to capture the time difference between 2 pins changing their electrical state. To do this you can use pulseIn().
Using your example in your question we get...
if (13 == HIGH) {
millis = pulseIn(13, LOW);
}
That will give you the duration between the pin going high and then going low, stored in the variable millis. It's good practice to store it in a long.