CODEWITHSUNDEEP
arduinoserial-portinterrupt
naps1saps
naps1saps

Reputation: 413

How do I read serial between interrupts on Arduino?

I have steppers stepping during an interrupt timer at 50 and have all my code working between the interrupts until I tried reading serial commands more than one character long.

I'm getting dropped bytes so my strings are missing a letter every 4-5 chars. I researched all day to try and figure out a solution but have come up with nothing. If I don't use an interrupt my stepper stops for 2 seconds reading a one char serial input as a string.

My goal is to have a remote control app sending speed commands. I need help working this problem out.

https://sourceforge.net/p/open-slider/code/ci/master/tree/OpenSliderFirmware/

String incomingString = "";
if (Serial.available() > 0) {
    incomingString = Serial.readString();
    Serial.println(incomingString);
}

Using Accelstepper library

interrupt:

//Interrupt Timer1
void ISR_stepperManager() {
    Slide.runSpeed();
    Xaxis.runSpeed();
    Yaxis.runSpeed(); 
}

Upvotes: 2

Views: 3153

Answers (2)

naps1saps
naps1saps

Reputation: 413

Quick answer: you don't if the interrupt timer is cutting in too often.

I resolved the problem by using a variable interrupt timer and a step multiplier. Basically the steps are called every time the timer interrupts instead of checking millis inside the interrupt function. This solved many issues. The speed of the stepper is now controlled by the interrupt timer. This gave me more free cycles to fully read the incoming serial without corruption and improved efficiency. Calling more steps per cycle when doing over 4k steps/s also improved efficiency requiring less cycles for a high rate of steps.

The serial is processed one char per cycle to prevent blocking.

Overall, if you are using serial and an interrupt timer, any interrupt happening < 100us you should be cautious how much code you are running during the interrupt. It will cause issues with incoming serial and user inputs. A few lines of code in a 25us timer interrupt, incoming serial will not function.

Upvotes: 1

YoavShtainer
YoavShtainer

Reputation: 68

i'm not sure if it will help to your problem, but i saw along the time that the String type is not safe to use when other things need to happened. i prefer to use char array and read one char at a time.

while(Serial.available())
{
 data[x] = Serial.read();
 x++;
}

i'm finding it much more reliable.

hope it's help!

Upvotes: 0

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