From 35a55d5757c1ed415cd5c9b4225f5c2011f0fbf1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Stefan=20Br=C3=83=C2=BCns?= Date: Sun, 12 Mar 2017 06:00:26 +0100 Subject: [PATCH] SOFT_PWM: Implement dithering if SOFT_PWM_SCALE is 1 or more MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit If dithering is enabled, the remainder of the soft_pwm_X duty value at turnoff time is added to the next cycle. If e.g. the duty is set to 9 and SCALE is set to 2, the PWM will be active for 8 counts for 3 cycles and 12 counts on each fourth cycle, i.e. the average is 9 cycles. This compensates the resolution loss at higher scales and allows running fans with SOFT_PWM with significantly reduced noise. Signed-off-by: Stefan Brüns --- Marlin/Configuration.h | 6 ++++++ Marlin/temperature.cpp | 44 +++++++++++++++++++++++++----------------- 2 files changed, 32 insertions(+), 18 deletions(-) diff --git a/Marlin/Configuration.h b/Marlin/Configuration.h index 96b1ededc..d290af575 100644 --- a/Marlin/Configuration.h +++ b/Marlin/Configuration.h @@ -1424,6 +1424,12 @@ // at zero value, there are 128 effective control positions. #define SOFT_PWM_SCALE 0 +// If SOFT_PWM_SCALE is set to a value higher than 0, dithering can +// be used to mitigate the associated resolution loss. If enabled, +// some of the PWM cycles are stretched so on average the wanted +// duty cycle is attained. +//#define SOFT_PWM_DITHER + // Temperature status LEDs that display the hotend and bed temperature. // If all hotends and bed temperature and temperature setpoint are < 54C then the BLUE led is on. // Otherwise the RED led is on. There is 1C hysteresis. diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp index 66390d8c7..0cec6fc7c 100644 --- a/Marlin/temperature.cpp +++ b/Marlin/temperature.cpp @@ -1521,7 +1521,7 @@ void Temperature::isr() { static uint8_t state_heater_ ## n = 0; \ static uint8_t state_timer_heater_ ## n = 0 #else - #define ISR_STATICS(n) static uint8_t soft_pwm_ ## n + #define ISR_STATICS(n) static uint8_t soft_pwm_ ## n = 0 #endif // Statics per heater @@ -1544,43 +1544,51 @@ void Temperature::isr() { #endif #if DISABLED(SLOW_PWM_HEATERS) + constexpr uint8_t pwm_mask = + #if ENABLED(SOFT_PWM_DITHER) + _BV(SOFT_PWM_SCALE) - 1 + #else + 0 + #endif + ; + /** * Standard PWM modulation */ if (pwm_count >= 127) { - pwm_count = 0; - soft_pwm_0 = soft_pwm[0]; - WRITE_HEATER_0(soft_pwm_0 > 0 ? HIGH : LOW); + pwm_count -= 127; + soft_pwm_0 = (soft_pwm_0 & pwm_mask) + soft_pwm[0]; + WRITE_HEATER_0(soft_pwm_0 > pwm_mask ? HIGH : LOW); #if HOTENDS > 1 - soft_pwm_1 = soft_pwm[1]; - WRITE_HEATER_1(soft_pwm_1 > 0 ? HIGH : LOW); + soft_pwm_1 = (soft_pwm_1 & pwm_mask) + soft_pwm[1]; + WRITE_HEATER_1(soft_pwm_1 > pwm_mask ? HIGH : LOW); #if HOTENDS > 2 - soft_pwm_2 = soft_pwm[2]; - WRITE_HEATER_2(soft_pwm_2 > 0 ? HIGH : LOW); + soft_pwm_2 = (soft_pwm_2 & pwm_mask) + soft_pwm[2]; + WRITE_HEATER_2(soft_pwm_2 > pwm_mask ? HIGH : LOW); #if HOTENDS > 3 - soft_pwm_3 = soft_pwm[3]; - WRITE_HEATER_3(soft_pwm_3 > 0 ? HIGH : LOW); + soft_pwm_3 = (soft_pwm_3 & pwm_mask) + soft_pwm[3]; + WRITE_HEATER_3(soft_pwm_3 > pwm_mask ? HIGH : LOW); #endif #endif #endif #if HAS_HEATER_BED - soft_pwm_BED = soft_pwm_bed; - WRITE_HEATER_BED(soft_pwm_BED > 0 ? HIGH : LOW); + soft_pwm_BED = (soft_pwm_BED & pwm_mask) + soft_pwm_bed; + WRITE_HEATER_BED(soft_pwm_BED > pwm_mask ? HIGH : LOW); #endif #if ENABLED(FAN_SOFT_PWM) #if HAS_FAN0 - soft_pwm_fan[0] = fanSpeedSoftPwm[0] >> 1; - WRITE_FAN(soft_pwm_fan[0] > 0 ? HIGH : LOW); + soft_pwm_fan[0] = (soft_pwm_fan[0] & pwm_mask) + fanSpeedSoftPwm[0] >> 1; + WRITE_FAN(soft_pwm_fan[0] > pwm_mask ? HIGH : LOW); #endif #if HAS_FAN1 - soft_pwm_fan[1] = fanSpeedSoftPwm[1] >> 1; - WRITE_FAN1(soft_pwm_fan[1] > 0 ? HIGH : LOW); + soft_pwm_fan[1] = (soft_pwm_fan[1] & pwm_mask) + fanSpeedSoftPwm[1] >> 1; + WRITE_FAN1(soft_pwm_fan[1] > pwm_mask ? HIGH : LOW); #endif #if HAS_FAN2 - soft_pwm_fan[2] = fanSpeedSoftPwm[2] >> 1; - WRITE_FAN2(soft_pwm_fan[2] > 0 ? HIGH : LOW); + soft_pwm_fan[2] = (soft_pwm_fan[2] & pwm_mask) + fanSpeedSoftPwm[2] >> 1; + WRITE_FAN2(soft_pwm_fan[2] > pwm_mask ? HIGH : LOW); #endif #endif }