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# Test machine.PWM, frequency and duty cycle (using machine.time_pulse_us).
#
# IMPORTANT: This test requires hardware connections: the PWM-output and pulse-input
# pins must be wired together (see the variable `pwm_pulse_pins`).
import sys
import time
try:
from machine import time_pulse_us, Pin, PWM
except ImportError:
print("SKIP")
raise SystemExit
import unittest
pwm_freq_limit = 1000000
freq_margin_per_thousand = 0
duty_margin_per_thousand = 0
timing_margin_us = 5
# Configure pins based on the target.
if "esp32" in sys.platform:
pwm_pulse_pins = ((4, 5),)
freq_margin_per_thousand = 2
duty_margin_per_thousand = 1
timing_margin_us = 20
elif "esp8266" in sys.platform:
pwm_pulse_pins = ((4, 5),)
pwm_freq_limit = 1_000
duty_margin_per_thousand = 3
timing_margin_us = 50
elif "mimxrt" in sys.platform:
if "Teensy" in sys.implementation._machine:
# Teensy 4.x
pwm_pulse_pins = (
("D0", "D1"), # FLEXPWM X and UART 1
("D2", "D3"), # FLEXPWM A/B
("D11", "D12"), # QTMR and MOSI/MISO of SPI 0
)
else:
pwm_pulse_pins = (("D0", "D1"),)
elif "rp2" in sys.platform:
pwm_pulse_pins = (("GPIO0", "GPIO1"),)
elif "samd" in sys.platform:
pwm_pulse_pins = (("D0", "D1"),)
if "SAMD21" in sys.implementation._machine:
# MCU is too slow to capture short pulses.
pwm_freq_limit = 2_000
else:
print("Please add support for this test on this platform.")
raise SystemExit
# Test a specific frequency and duty cycle.
def _test_freq_duty(self, pulse_in, pwm, freq, duty_u16):
print("freq={:<5} duty_u16={:<5} :".format(freq, duty_u16), end="")
# Check configured freq/duty_u16 is within error bound.
freq_error = abs(pwm.freq() - freq) * 1000 // freq
duty_error = abs(pwm.duty_u16() - duty_u16) * 1000 // (duty_u16 or 1)
print(" freq={} freq_er={}".format(pwm.freq(), freq_error), end="")
print(" duty={} duty_er={}".format(pwm.duty_u16(), duty_error), end="")
print(" :", end="")
self.assertLessEqual(freq_error, freq_margin_per_thousand)
self.assertLessEqual(duty_error, duty_margin_per_thousand)
# Calculate expected timing.
expected_total_us = 1_000_000 // freq
expected_high_us = expected_total_us * duty_u16 // 65535
expected_low_us = expected_total_us - expected_high_us
expected_us = (expected_low_us, expected_high_us)
timeout = 2 * expected_total_us
# Wait for output to settle.
time_pulse_us(pulse_in, 0, timeout)
time_pulse_us(pulse_in, 1, timeout)
if duty_u16 == 0 or duty_u16 == 65535:
# Expect a constant output level.
no_pulse = (
time_pulse_us(pulse_in, 0, timeout) < 0 and time_pulse_us(pulse_in, 1, timeout) < 0
)
self.assertTrue(no_pulse)
if expected_high_us == 0:
# Expect a constant low level.
self.assertEqual(pulse_in(), 0)
else:
# Expect a constant high level.
self.assertEqual(pulse_in(), 1)
else:
# Test timing of low and high pulse.
n_averaging = 10
for level in (0, 1):
t = 0
time_pulse_us(pulse_in, level, timeout)
for _ in range(n_averaging):
t += time_pulse_us(pulse_in, level, timeout)
t //= n_averaging
expected = expected_us[level]
print(" level={} timing_er={}".format(level, abs(t - expected)), end="")
self.assertLessEqual(abs(t - expected), timing_margin_us)
print()
# Test a specific frequency with multiple duty cycles.
def _test_freq(self, freq):
print()
self.pwm.freq(freq)
for duty in (0, 10, 25, 50, 75, 90, 100):
duty_u16 = duty * 65535 // 100
if sys.platform == "esp32":
# TODO why is this bit needed to get it working on esp32?
self.pwm.init(freq=freq, duty_u16=duty_u16)
time.sleep(0.1)
self.pwm.duty_u16(duty_u16)
_test_freq_duty(self, self.pulse_in, self.pwm, freq, duty_u16)
# Given a set of pins, this test class will test multiple frequencies and duty cycles.
class TestBase:
@classmethod
def setUpClass(cls):
print("set up pins:", cls.pwm_pin, cls.pulse_pin)
cls.pwm = PWM(cls.pwm_pin)
cls.pulse_in = Pin(cls.pulse_pin, Pin.IN)
@classmethod
def tearDownClass(cls):
cls.pwm.deinit()
def test_freq_50(self):
_test_freq(self, 50)
def test_freq_100(self):
_test_freq(self, 100)
def test_freq_500(self):
_test_freq(self, 500)
def test_freq_1000(self):
_test_freq(self, 1000)
@unittest.skipIf(pwm_freq_limit < 2000, "frequency too high")
def test_freq_2000(self):
_test_freq(self, 2000)
@unittest.skipIf(pwm_freq_limit < 5000, "frequency too high")
def test_freq_5000(self):
_test_freq(self, 5000)
@unittest.skipIf(pwm_freq_limit < 10000, "frequency too high")
def test_freq_10000(self):
_test_freq(self, 10000)
# Generate test classes, one for each set of pins to test.
for pwm, pulse in pwm_pulse_pins:
cls_name = "Test_{}_{}".format(pwm, pulse)
globals()[cls_name] = type(
cls_name, (TestBase, unittest.TestCase), {"pwm_pin": pwm, "pulse_pin": pulse}
)
if __name__ == "__main__":
unittest.main()
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