PWM Help

[f1test]

I need PWM signal with 4 Hz.

My code is:
"
OPTION.PWMFREQ(4)
pwm(15)=100
while 1
a=a+1

wlog a
pause 500
wend
"
My multimeter show 100 Hz. the oscilloscope as well

I can reach frequencies higher than 100 hz but not lower. Does anyone know why?

[cicciocb]

It looks that you are using the ESP8266.

The PWM lower frequency is limited at 100 Hz

https://arduino-esp8266.readthedocs.io/ ... log-output

[f1test]

Yes is 8266.

I think the limitation is not hardware. In micropython I managed to go down to 4 Hz
"
import machine

p4 = machine.Pin(4)

pwm4 = machine.PWM(p4)

pwm4.freq(4)

pwm4.duty(50)

"
I even tested 1Hz, it works correctly.

[f1test]

I did another test in Arduino. And here the frequency can be reduced below 100 Hz.

'
const int ledPin = 4;

void setup() {
analogWriteFreq(4);
analogWrite(ledPin, 17);
}

void loop() {


}
Maybe these languages ​​use other tricks to lower the frequency below 100 Hz.

[BeanieBots]

I've just tried:-
PIN.TONE pin, freq [,duration]
and it goes down to 1Hz.

Another option might be to use a timer and set the period if you want very low frequencies.
Not sure how stable that would be if you are also using WIFI and/or interrupts.
I guess it really depends what you need the pulses for.

[f1test]

The example proves that the hardware can go down to 1 Hz.
Pin.Tone generates a signal without the possibility of changing the duty cycle.
I will try with Timer0.

Thank

[f1test]

This is my attempt. Use Timer0 and Timer1.
If you can, please improve it
" pin.mode 4 , output
timer_0=1
frecventa = 4
duty=0.2
perioada = 1000/frecventa
timp_calc = perioada * duty
timp_ramas = perioada-timp_calc
wlog timp_calc
wlog timp_ramas

timer0 timp_calc, Led_Off

wait


Led_Off:

pin(4)=0
timer0 0
timer1 timp_ramas, led_on
return

Led_on:

pin(4)=1
timer0 timp_calc, Led_Off
timer1 0
return
"

Changing the value of the Duty variable from 0.01 to 0.99 can be used to change the load factor.
Changing the value of the frecventa variable changes the PWM frequency

[BeanieBots]

Something like this should get you close.
You might need to fiddle with the numbers a little to compensate for errors in the timer period and code execution time.

Code: [Local Link Removed for Guests]

MyPin = 2
Pin.mode MyPin, output
Duty = 50       'Set your desired % duty cycle
Frequency = 4   'Set your desired frequency

Period = 1/Frequency * 1000
OnTime = Period * Duty / 100

Timer0 Period, Doit

wait

Doit:
 Pin(MyPin) = 1
 Pause OnTime
 Pin(MyPin)=0
Return