From 3752d9aca8f72ac397623669405ee739bfb7c53c Mon Sep 17 00:00:00 2001 From: Scott Lahteine Date: Sun, 9 Oct 2016 10:06:31 -0500 Subject: [PATCH] Fix timer comments --- Marlin/stepper.cpp | 24 +++++++++++++++++++----- Marlin/temperature.cpp | 25 ++++++++++++++++++++----- 2 files changed, 39 insertions(+), 10 deletions(-) diff --git a/Marlin/stepper.cpp b/Marlin/stepper.cpp index 7889b8a883..ebe55b9ada 100644 --- a/Marlin/stepper.cpp +++ b/Marlin/stepper.cpp @@ -311,8 +311,20 @@ void Stepper::set_directions() { #endif // !ADVANCE && !LIN_ADVANCE } -// "The Stepper Driver Interrupt" - This timer interrupt is the workhorse. -// It pops blocks from the block_buffer and executes them by pulsing the stepper pins appropriately. +/** + * Stepper Driver Interrupt + * + * Directly pulses the stepper motors at high frequency. + * Timer 1 runs at a base frequency of 2MHz, with this ISR using OCR1A compare mode. + * + * OCR1A Frequency + * 1 2 MHz + * 50 40 KHz + * 100 20 KHz - capped max rate + * 200 10 KHz - nominal max rate + * 2000 1 KHz - sleep rate + * 4000 500 Hz - init rate + */ ISR(TIMER1_COMPA_vect) { Stepper::isr(); } void Stepper::isr() { @@ -323,7 +335,7 @@ void Stepper::isr() { if ((cleaning_buffer_counter == 1) && (SD_FINISHED_STEPPERRELEASE)) enqueue_and_echo_commands_P(PSTR(SD_FINISHED_RELEASECOMMAND)); #endif cleaning_buffer_counter--; - OCR1A = 200; + OCR1A = 200; // Run at max speed - 10 KHz return; } @@ -348,7 +360,7 @@ void Stepper::isr() { #if ENABLED(Z_LATE_ENABLE) if (current_block->steps[Z_AXIS] > 0) { enable_z(); - OCR1A = 2000; //1ms wait + OCR1A = 2000; // Run at slow speed - 1 KHz return; } #endif @@ -358,7 +370,7 @@ void Stepper::isr() { // #endif } else { - OCR1A = 2000; // 1kHz. + OCR1A = 2000; // Run at slow speed - 1 KHz return; } } @@ -903,6 +915,7 @@ void Stepper::init() { // output mode = 00 (disconnected) TCCR1A &= ~(3 << COM1A0); TCCR1A &= ~(3 << COM1B0); + // Set the timer pre-scaler // Generally we use a divider of 8, resulting in a 2MHz timer // frequency on a 16MHz MCU. If you are going to change this, be @@ -910,6 +923,7 @@ void Stepper::init() { // create_speed_lookuptable.py TCCR1B = (TCCR1B & ~(0x07 << CS10)) | (2 << CS10); + // Init Stepper ISR to 122 Hz for quick starting OCR1A = 0x4000; TCNT1 = 0; ENABLE_STEPPER_DRIVER_INTERRUPT(); diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp index 42f68f4381..285871a879 100644 --- a/Marlin/temperature.cpp +++ b/Marlin/temperature.cpp @@ -1371,7 +1371,7 @@ void Temperature::set_current_temp_raw() { * Timer 0 is shared with millies so don't change the prescaler. * * This ISR uses the compare method so it runs at the base - * frequency (16 MHz / 256 = 62500 Hz), but at the TCNT0 set + * frequency (16 MHz / 64 / 256 = 976.5625 Hz), but at the TCNT0 set * in OCR0B above (128 or halfway between OVFs). * * - Manage PWM to all the heaters and fan @@ -1485,9 +1485,16 @@ void Temperature::isr() { #endif #endif - // 488.28 Hz (or 1:976.56, 2:1953.12, 3:3906.25, 4:7812.5, 5:7812.5 6:15625, 6:15625 7:31250) + // SOFT_PWM_SCALE to frequency: + // + // 0: 16000000/64/256/128 = 7.6294 Hz + // 1: / 64 = 15.2588 Hz + // 2: / 32 = 30.5176 Hz + // 3: / 16 = 61.0352 Hz + // 4: / 8 = 122.0703 Hz + // 5: / 4 = 244.1406 Hz pwm_count += _BV(SOFT_PWM_SCALE); - pwm_count &= 0x7f; + pwm_count &= 0x7F; #else // SLOW_PWM_HEATERS @@ -1586,10 +1593,18 @@ void Temperature::isr() { #endif #endif //FAN_SOFT_PWM + // SOFT_PWM_SCALE to frequency: + // + // 0: 16000000/64/256/128 = 7.6294 Hz + // 1: / 64 = 15.2588 Hz + // 2: / 32 = 30.5176 Hz + // 3: / 16 = 61.0352 Hz + // 4: / 8 = 122.0703 Hz + // 5: / 4 = 244.1406 Hz pwm_count += _BV(SOFT_PWM_SCALE); - pwm_count &= 0x7f; + pwm_count &= 0x7F; - // increment slow_pwm_count only every 64 pwm_count circa 65.5ms + // increment slow_pwm_count only every 64 pwm_count (e.g., every 8s) if ((pwm_count % 64) == 0) { slow_pwm_count++; slow_pwm_count &= 0x7f;