I'm trying to control a servo with a PWM signal with an ESP32 with micropython. I cannot seem to get the servo to move and therefore would like to check my PWM signal.
I created a testing script to generate a PWM signal on GPIO32 and measure this back on GPIO36. I connected a jumper wire between 32 and 36 and I'm using the following code:
"""Testing script"""
import machine
from machine import Pin, PWM
import utime
# PWM on pin 32
p_out = Pin(32, Pin.OUT)
pwm = PWM(p_out)
f = 500
pwm.freq(f)
dc = 512
pwm.duty(dc)
# Measure on pin 36
p_echo = Pin(36, Pin.IN)
while True:
timeout_us = int(2 * 1 / f * 1e6)
print(
f"Trying to measure pulse length of {dc/1024*1 / f * 1e6} us with a timeout of {timeout_us} us"
)
print(f"Pulse length: {machine.time_pulse_us(p_echo,0,timeout_us)} us")
utime.sleep_ms(100)
The only thing I get back is
Trying to measure pulse length of 1000.0 us with a timeout of 4000 us
Pulse length: -1 us
I'm obviously missing something here. The documentation says:
machine.time_pulse_us(pin, pulse_level, timeout_us=1000000, /)
Time a pulse on the given pin, and return the duration of the pulse in microseconds. The pulse_level argument should be 0 to time a low pulse or 1 to time a high pulse.
If the current input value of the pin is different to pulse_level, the function first (*) waits until the pin input becomes equal to pulse_level, then (**) times the duration that the pin is equal to pulse_level. If the pin is already equal to pulse_level then timing starts straight away.
The function will return -2 if there was timeout waiting for condition marked (*) above, and -1 if there was timeout during the main measurement, marked (**) above. The timeout is the same for both cases and given by timeout_us (which is in microseconds).
Seems like the timeout expired and nothing happened. I don't really have something else to verify that the PWM output is actually doing something like a scope.
