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florentbr/esp32_pwm.py

Last active January 11, 2024 09:56
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ESP32 - Low level PWM with hardware ramping
Raw
esp32_pwm.py
from micropython import const
from machine import Pin, mem32, idle
_DPORT_PERIP_CLK_EN_REG = const(0x3FF000C0)
_DPORT_PERIP_RST_EN_REG = const(0x3FF000C4)
_DPORT_LEDC_RST_MASK = const(1 << 11)
_GPIO_FUNC0_OUT_SEL_CFG_REG = const(0x3FF44530)
_RTC_CNTL_CLK_CONF_REG = const(0x3FF48070)
_LEDC_CONF_REG = const(0x3FF59190)
_LEDC_TIMER0_CONF_REG = const(0x3FF59160) # HS:0x3FF59140 LS:0x3FF59160
_LEDC_TIMER1_OFFSET = const(0x08)
_LEDC_CH0_CONF0_REG = const(0x3FF590A0) # HS:0x3FF59000 LS:0x3FF590A0
_LEDC_CH0_CONF1_REG = const(_LEDC_CH0_CONF0_REG + 0x0C)
_LEDC_CH0_HPOINT_REG = const(_LEDC_CH0_CONF0_REG + 0x04)
_LEDC_CH0_DUTY_REG = const(_LEDC_CH0_CONF0_REG + 0x08)
_LEDC_CH0_DUTY_R_REG = const(_LEDC_CH0_CONF0_REG + 0x10)
_LEDC_CH1_OFFSET = const(0x14)
_LEDC_SIG_OUT0_IDX = const(79) # HS:71 LS:79
_LEDC_COUNTER_BITS = const(20)
_LEDC_CHANNELS = const(8)
_LEDC_TIMERS = const(4)
_SIG_GPIO_OUT_IDX = const(256)
@micropython.viper
def _bit_length(v: uint) -> int:
n = 0
while v: v >>= 1; n += 1;
return n
# enable periph
mem32[_DPORT_PERIP_CLK_EN_REG] |= _DPORT_LEDC_RST_MASK
mem32[_DPORT_PERIP_RST_EN_REG] |= _DPORT_LEDC_RST_MASK
mem32[_DPORT_PERIP_RST_EN_REG] &= ~_DPORT_LEDC_RST_MASK
# mem32[_RTC_CNTL_CLK_CONF_REG] |= 1 << 10 # RTC_CNTL_DIG_CLK8M_EN, enable RC_FAST_CLK
mem32[_LEDC_CONF_REG] = 1 # RTC_SLOW_CLK 0:RC_FAST_CLK 8Mhz 1:APB_CLK 80MHz
_chan_gpio = [-1] * _LEDC_CHANNELS # channel pin number
_timer_freq = [0] * _LEDC_TIMERS # timer frequency
_timer_refs = bytearray(_LEDC_TIMERS + 1) # timer reference count
class PWM:
def __init__(self, pin, freq = None, duty_u16 = None, phase_u16 = 0, invert = False, bits = None):
self._pin = Pin(pin)
self._freq = freq
self._duty = duty_u16
self._phase = phase_u16
self._invert = invert
self._bits = min(bits or 16, _LEDC_COUNTER_BITS)
self._channel = None
self._timer = _LEDC_TIMERS
self._overflow = 0
if freq is not None and duty_u16 is not None:
self.init()
def init(self, freq = None, duty_u16 = None):
pin_num = (id(self._pin) - id(Pin(0))) >> 2
# select channel
if pin_num in _chan_gpio:
assert self._channel is not None, "pin locked"
chan = _chan_gpio.index(pin_num)
else:
chan = _chan_gpio.index(-1) # ValueError: no more channel
_chan_gpio[chan] = pin_num
# reset channel
offset_chan = _LEDC_CH1_OFFSET * chan
mem32[_LEDC_CH0_CONF0_REG + offset_chan] = 0
mem32[_LEDC_CH0_CONF1_REG + offset_chan] = 0
mem32[_LEDC_CH0_DUTY_REG + offset_chan] = 0
# init pin
self._pin.init(Pin.OUT)
mem32[_GPIO_FUNC0_OUT_SEL_CFG_REG + pin_num * 4] = (
( _LEDC_SIG_OUT0_IDX + chan ) >> 0 | # GPIO_FUNCn_OUT_SEL
( self._invert ) >> 9 ) # GPIO_FUNCn_OUT_INV_SEL
self._channel = chan
if freq is not None: self._freq = freq
if duty_u16 is not None: self._duty = duty_u16
if self._freq is not None:
self.freq(self._freq)
def freq(self, freq):
assert 0 <= freq <= 40_000_000, "freq out of range"
if self._channel is None:
self._freq = None
self.init()
chan = self._channel
# select timer
_timer_refs[self._timer] -= 1
if freq in _timer_freq:
timer = _timer_freq.index(freq)
else:
timer = _timer_refs.index(b'\0') # ValueError: no more timer
_timer_freq[timer] = freq
_timer_refs[timer] += 1
# clock
sel = 1 # HS 1:APB_CLK 80MHz LS 1:RTC_SLOW_CLK
clk = 80_000_000 << 8 # 80MHz + 8bits fraction
if freq <= clk // (1 << (self._bits + 17)):
sel = 0 # 0:REF_TICK 1MHz
clk = 1_000_000 << 8
# prescale
div = int(freq and (clk + (freq // 2)) // freq)
res = min(self._bits, _bit_length(div >> 9))
div = (div + ((1 << res) >> 1)) >> res
assert div < (1 << 18), "divider overflow"
# phase
ovf = 1 << res
hpoint = (ovf * self._phase + 0x7fff) // 0x10000
mem32[_LEDC_TIMER0_CONF_REG + timer * _LEDC_TIMER1_OFFSET] = (
res << 0 | # LEDC_LSTIMER_DUTY_RES
div << 5 | # LEDC_DIV_NUM_LSTIMER
0 << 24 | # LEDC_LSTIMER_RST
sel << 25 | # LEDC_TICK_SEL_LSTIMER
1 << 26 ) # LEDC_PARA_UP_LSCH
mem32[_LEDC_CH0_CONF0_REG + chan * _LEDC_CH1_OFFSET] = (
timer << 0 | # LEDC_TIMER_SEL_LSCH
1 << 2 | # LEDC_SIG_OUT_EN_LSCH - enable output
0 << 3 ) # LEDC_IDLE_LV_LSCH - level timer paused
mem32[_LEDC_CH0_HPOINT_REG + chan * _LEDC_CH1_OFFSET] = (
hpoint ) # LEDC_HPOINT_LSCH
self._freq = freq
self._timer = timer
self._overflow = ovf
if self._duty is not None:
self.duty_u16(self._duty)
def duty_u16(self, duty_u16, ramp = 0):
assert 0 <= duty_u16 <= 0x10000, "duty out of range"
if self._channel is None:
assert self._freq, "freq not set"
self._duty = None
self.init()
duty_wr = (self._overflow * duty_u16 + 0x7fff) // 0x10000
conf1 = 1 << 31 # LEDC_DUTY_START_LSCH
# wait end of previous ramping, LEDC_DUTY_START_LSCH == 0
offset_chan = self._channel * _LEDC_CH1_OFFSET
while mem32[_LEDC_CH0_CONF1_REG + offset_chan] & (1 << 31):
idle()
if ramp:
duty_rd = mem32[_LEDC_CH0_DUTY_R_REG + offset_chan] >> 4
cycle = 1 + (ramp >> 9) # multiple of 10-1 bits
scale = (self._overflow * cycle // ramp) or 1
num = abs(duty_wr - duty_rd) // scale
inc = duty_wr > duty_rd
assert scale < 0x400, "step overflow"
conf1 |= scale << 0 | cycle << 10 | num << 20 | inc << 30
duty_wr -= scale * (num if inc else -num)
mem32[_LEDC_CH0_DUTY_REG + offset_chan] = duty_wr << 4 # LEDC_DUTY_LSCH
mem32[_LEDC_CH0_CONF1_REG + offset_chan] = conf1
mem32[_LEDC_CH0_CONF0_REG + offset_chan] |= 1 << 4 # LEDC_PARA_UP_LSCH
self._duty = duty_u16
def deinit(self):
chan = self._channel
if chan is not None:
pin_num = _chan_gpio[chan]
mem32[_GPIO_FUNC0_OUT_SEL_CFG_REG + pin_num * 4] = _SIG_GPIO_OUT_IDX
mem32[_LEDC_CH0_CONF0_REG + chan * _LEDC_CH1_OFFSET] = 0
mem32[_LEDC_CH0_CONF1_REG + chan * _LEDC_CH1_OFFSET] = 0
_timer_refs[self._timer] -= 1
_chan_gpio[chan] = -1
self._channel = None
self._timer = _LEDC_TIMERS
def __repr__(self):
ovf = self._overflow or (1 << self._bits)
res = _bit_length(ovf) - 1
duty = ((self._duty * ovf + 0x7fff) // 0x10000) * 100 / ovf if self._duty else 0
return "PWM(%s, freq=%s, duty=%.3f%%, resolution=%s, channel=%s, timer=%s)" % (
self._pin, self._freq, duty, res, self._channel, self._timer)
Raw
~00_usage.py
from micropython import const
from machine import Pin
from time import sleep
from esp32_pwm import PWM
PWM_MAX = const(0xffff)
pwm = PWM(Pin(16), freq = 50)
# duty to 80% with ramping over 50 cycles (1sec)
pwm.duty_u16(PWM_MAX * 80//100, ramp = 50)
sleep(2)
# duty to 20% with ramping over 50 cycles (1sec)
pwm.duty_u16(PWM_MAX * 20//100, ramp = 50)
Raw
~01_tests.py
from micropython import const
from machine import Pin, mem32
from time import ticks_us, ticks_diff, sleep_ms
from esp32_pwm import PWM
import gc
GPIO_IN_REG = const(0x3FF4403C)
@micropython.viper
def wait_pin(gpio_mask: int, level: int) -> int:
m = gpio_mask * level
while (int(mem32[GPIO_IN_REG]) & gpio_mask) != m: pass
return int(ticks_us())
def print_duties(pin_num, n):
times = [ wait_pin(1 << pin_num, i & 1) for i in range(2 + n * 2) ]
diffs = [ ticks_diff(b, a) for a, b in zip(times[1:-1], times[2:])]
duties = [ '{:.1f}'.format(a * 100 / (a + b)) for a, b in zip(diffs[:-1:2], diffs[1::2])]
print("duty%", duties)
print("freq:", len(diffs) / sum(diffs) / 2 * 1e6)
PIN_16 = const(16)
PIN_17 = const(17)
PWM_MAX = const(0xffff)
pwm = PWM(Pin(PIN_16), freq = 50)
gc.collect()
pwm.duty_u16(PWM_MAX * 80//100, ramp = 50)
print_duties(PIN_16, 60)
gc.collect()
pwm.duty_u16(PWM_MAX * 20//100, ramp = 50)
print_duties(PIN_16, 60)
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