L298N Motor Driver using pwm code not working..

[HenrikOlsson]

Hi,
I don't really follow your coding but you have a main loop which constantly (I mean thousands of times per second) keeps setting the dutycycle to some value. When the interrupt fires, decide which way to turn (if any) and set the dutycycle, don't change it the main loop. BTW, does 10Hz really work? Also, in your previous code I got the impression that the sensors were analog (you used ADCIN to read them) but now they are digital?

/Henrik.

EDIT: One more thing, you don't seem to reload the timer value in the ISR.
Since the timer is freerunning and generating an interrupt on overflow, with a prescaler of 8 and a 4MHz x-tal the interrupt frequency of 4000000/4/8/65536=1.9Hz, I think you need to run faster than that.

[tacbanon]

Hi Henrik, thanks you for your comments..I guess I have to rearrange my codes.

don't change it the main loop.

Does this mean I have to remove this in the main loop..

; Start rolling
HPWM 1 ,Gear[i],10
HPWM 2 ,Gear[i],10

and place it in a sub program?

I did remove the analog reading to digital because I thought it will better...don't you think so?

Regarding the timer, should this be the value T1CON = %00100001 ?
I really appreciate for answering my questions..not really all clear to me at this time but I hope I will learn some if not all.
BTW do you think it is best to have a fix speed instead of changing from time to time?

regards,
tacbanon

[HenrikOlsson]

Hi,
HPWM works in the background, once you tell it to output a certain dutycycle with a certain frequency it does that in hardware. There's no need to continously execute the HPWM commands like your doing in your main loop.

If you change the prescaler to 1:1 you'll get an interrupt every 65536us or around 15Hz, I'd try that as a starting point. If you need faster interrupt rate than that you need to preload the TMR1 register in the ISR so that it doesn't start from 0. If you load with 55536 there will be 10000 cycles (or 10000us in this case) untill the next interrupt.

I have no idea if analog or digital sensor is best. I don't even know what sensors you're using....

If you have two sensors, one on "each side" of the line then I think two speeds for each motor should do. Run both motor at the lower speed to go straight forward, increase the speed of one motor to turn. (Or do the oposite if you want).

[tacbanon]

Hi, thanks...I will try your suggestions regarding the timer/interrupt implementation...but I still don't get what you meant HPWM working on the background...my question probably is how I can change the speed parameter if I needed?

speedR var byte
speedL var byte
speedR = 150
speedL = 150
pause 2000
HPWM 1 ,speedR,10 ' Right Wheel
HPWM 2 ,speedL,10 ' Left wheel

Mainloop:

speedR = 100 ' new value of speed
speedL = 150 '

Goto Mainloop

regards,
tacbanon

[HenrikOlsson]

Hi,
To change the speed you to execute the HPWM command. What I'm "objecting" against is this:

Main:
HPWM.....
HPWM.....
Goto Main

When you do it this your trying to update the PWM generator thousands of time per second. What happens when you update it faster then the frequency it's outputting? I don't know the answer.

In the ISR, determine what duty cycles to send to each motor and execute the HPWM command there. That way you'll update the speed once each interrupt instead of thousands of times per second.

/Henrik.

[tacbanon]

Hi Henrik...many thanks for the kindly explaination...appreciate it very much...got it now.

regards,
tacbanon