diff -r 000000000000 -r 2c8ba1964db7 stepper.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/stepper.cpp Sat Nov 07 13:23:07 2015 +0100 @@ -0,0 +1,872 @@ +/* + stepper.c - stepper motor driver: executes motion plans using stepper motors + Part of Grbl + + Copyright (c) 2009-2011 Simen Svale Skogsrud + + Grbl is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + Grbl is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with Grbl. If not, see . +*/ + +/* The timer calculations of this module informed by the 'RepRap cartesian firmware' by Zack Smith + and Philipp Tiefenbacher. */ + +#include "Marlin.h" +#include "stepper.h" +#include "planner.h" +#include "temperature.h" +#include "ultralcd.h" +#include "language.h" +#include "led.h" +#include "speed_lookuptable.h" + + + +//=========================================================================== +//=============================public variables ============================ +//=========================================================================== +block_t *current_block; // A pointer to the block currently being traced +volatile bool endstop_z_hit=false; +bool old_z_min_endstop=false; + + +//=========================================================================== +//=============================private variables ============================ +//=========================================================================== +//static makes it inpossible to be called from outside of this file by extern.! + +// Variables used by The Stepper Driver Interrupt +static unsigned char out_bits; // The next stepping-bits to be output +static long counter_x, // Counter variables for the bresenham line tracer + counter_y, + counter_z, + counter_e; +volatile static unsigned long step_events_completed; // The number of step events executed in the current block +#ifdef ADVANCE + static long advance_rate, advance, final_advance = 0; + static long old_advance = 0; +#endif +static long e_steps[3]; +static long acceleration_time, deceleration_time; +//static unsigned long accelerate_until, decelerate_after, acceleration_rate, initial_rate, final_rate, nominal_rate; +static unsigned short acc_step_rate; // needed for deccelaration start point +static char step_loops; +static unsigned short OCR1A_nominal; + +volatile long endstops_trigsteps[3]={0,0,0}; +volatile long endstops_stepsTotal,endstops_stepsDone; +static volatile bool endstop_x_hit=false; +static volatile bool endstop_y_hit=false; + +static bool old_x_min_endstop=false; +static bool old_x_max_endstop=false; +static bool old_y_min_endstop=false; +static bool old_y_max_endstop=false; +static bool old_z_max_endstop=false; + +static bool check_endstops = true; + +volatile long count_position[NUM_AXIS] = { 0, 0, 0, 0}; +volatile char count_direction[NUM_AXIS] = { 1, 1, 1, 1}; + +//=========================================================================== +//=============================functions ============================ +//=========================================================================== + +#define CHECK_ENDSTOPS if(check_endstops) + +// intRes = intIn1 * intIn2 >> 16 +// uses: +// r26 to store 0 +// r27 to store the byte 1 of the 24 bit result +#define MultiU16X8toH16(intRes, charIn1, intIn2) \ +asm volatile ( \ +"clr r26 \n\t" \ +"mul %A1, %B2 \n\t" \ +"movw %A0, r0 \n\t" \ +"mul %A1, %A2 \n\t" \ +"add %A0, r1 \n\t" \ +"adc %B0, r26 \n\t" \ +"lsr r0 \n\t" \ +"adc %A0, r26 \n\t" \ +"adc %B0, r26 \n\t" \ +"clr r1 \n\t" \ +: \ +"=&r" (intRes) \ +: \ +"d" (charIn1), \ +"d" (intIn2) \ +: \ +"r26" \ +) + +// intRes = longIn1 * longIn2 >> 24 +// uses: +// r26 to store 0 +// r27 to store the byte 1 of the 48bit result +#define MultiU24X24toH16(intRes, longIn1, longIn2) \ +asm volatile ( \ +"clr r26 \n\t" \ +"mul %A1, %B2 \n\t" \ +"mov r27, r1 \n\t" \ +"mul %B1, %C2 \n\t" \ +"movw %A0, r0 \n\t" \ +"mul %C1, %C2 \n\t" \ +"add %B0, r0 \n\t" \ +"mul %C1, %B2 \n\t" \ +"add %A0, r0 \n\t" \ +"adc %B0, r1 \n\t" \ +"mul %A1, %C2 \n\t" \ +"add r27, r0 \n\t" \ +"adc %A0, r1 \n\t" \ +"adc %B0, r26 \n\t" \ +"mul %B1, %B2 \n\t" \ +"add r27, r0 \n\t" \ +"adc %A0, r1 \n\t" \ +"adc %B0, r26 \n\t" \ +"mul %C1, %A2 \n\t" \ +"add r27, r0 \n\t" \ +"adc %A0, r1 \n\t" \ +"adc %B0, r26 \n\t" \ +"mul %B1, %A2 \n\t" \ +"add r27, r1 \n\t" \ +"adc %A0, r26 \n\t" \ +"adc %B0, r26 \n\t" \ +"lsr r27 \n\t" \ +"adc %A0, r26 \n\t" \ +"adc %B0, r26 \n\t" \ +"clr r1 \n\t" \ +: \ +"=&r" (intRes) \ +: \ +"d" (longIn1), \ +"d" (longIn2) \ +: \ +"r26" , "r27" \ +) + +// Some useful constants + +#define ENABLE_STEPPER_DRIVER_INTERRUPT() TIMSK1 |= (1< +// +// The trapezoid is the shape the speed curve over time. It starts at block->initial_rate, accelerates +// first block->accelerate_until step_events_completed, then keeps going at constant speed until +// step_events_completed reaches block->decelerate_after after which it decelerates until the trapezoid generator is reset. +// The slope of acceleration is calculated with the leib ramp alghorithm. + +void st_wake_up() { + // TCNT1 = 0; + ENABLE_STEPPER_DRIVER_INTERRUPT(); +} + +FORCE_INLINE unsigned short calc_timer(unsigned short step_rate) { + unsigned short timer; + if(step_rate > MAX_STEP_FREQUENCY) step_rate = MAX_STEP_FREQUENCY; + + if(step_rate > 20000) { // If steprate > 20kHz >> step 4 times + step_rate = (step_rate >> 2)&0x3fff; + step_loops = 4; + } + else if(step_rate > 10000) { // If steprate > 10kHz >> step 2 times + step_rate = (step_rate >> 1)&0x7fff; + step_loops = 2; + } + else { + step_loops = 1; + } + + if(step_rate < (F_CPU/500000)) step_rate = (F_CPU/500000); + step_rate -= (F_CPU/500000); // Correct for minimal speed + if(step_rate >= (8*256)){ // higher step rate + unsigned short table_address = (unsigned short)&speed_lookuptable_fast[(unsigned char)(step_rate>>8)][0]; + unsigned char tmp_step_rate = (step_rate & 0x00ff); + unsigned short gain = (unsigned short)pgm_read_word_near(table_address+2); + MultiU16X8toH16(timer, tmp_step_rate, gain); + timer = (unsigned short)pgm_read_word_near(table_address) - timer; + } + else { // lower step rates + unsigned short table_address = (unsigned short)&speed_lookuptable_slow[0][0]; + table_address += ((step_rate)>>1) & 0xfffc; + timer = (unsigned short)pgm_read_word_near(table_address); + timer -= (((unsigned short)pgm_read_word_near(table_address+2) * (unsigned char)(step_rate & 0x0007))>>3); + } + if(timer < 100) { timer = 100; MYSERIAL.print(MSG_STEPPER_TO_HIGH); MYSERIAL.println(step_rate); }//(20kHz this should never happen) + return timer; +} + +// Initializes the trapezoid generator from the current block. Called whenever a new +// block begins. +FORCE_INLINE void trapezoid_generator_reset() { + #ifdef ADVANCE + advance = current_block->initial_advance; + final_advance = current_block->final_advance; + // Do E steps + advance steps + e_steps[current_block->active_extruder] += ((advance >>8) - old_advance); + old_advance = advance >>8; + #endif + deceleration_time = 0; + // step_rate to timer interval + acc_step_rate = current_block->initial_rate; + acceleration_time = calc_timer(acc_step_rate); + OCR1A = acceleration_time; + OCR1A_nominal = calc_timer(current_block->nominal_rate); + + + +// SERIAL_ECHO_START; +// SERIAL_ECHOPGM("advance :"); +// SERIAL_ECHO(current_block->advance/256.0); +// SERIAL_ECHOPGM("advance rate :"); +// SERIAL_ECHO(current_block->advance_rate/256.0); +// SERIAL_ECHOPGM("initial advance :"); +// SERIAL_ECHO(current_block->initial_advance/256.0); +// SERIAL_ECHOPGM("final advance :"); +// SERIAL_ECHOLN(current_block->final_advance/256.0); + +} + +// "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. +ISR(TIMER1_COMPA_vect) +{ + // If there is no current block, attempt to pop one from the buffer + if (current_block == NULL) { + // Anything in the buffer? + current_block = plan_get_current_block(); + if (current_block != NULL) { + current_block->busy = true; + trapezoid_generator_reset(); + counter_x = -(current_block->step_event_count >> 1); + counter_y = counter_x; + counter_z = counter_x; + counter_e = counter_x; + step_events_completed = 0; + + #ifdef Z_LATE_ENABLE + if(current_block->steps_z > 0) { + enable_z(); + OCR1A = 2000; //1ms wait + return; + } + #endif + +// #ifdef ADVANCE +// e_steps[current_block->active_extruder] = 0; +// #endif + } + else { + OCR1A=2000; // 1kHz. + } + } + + if (current_block != NULL) { + // Set directions TO DO This should be done once during init of trapezoid. Endstops -> interrupt + out_bits = current_block->direction_bits; + + // Set direction en check limit switches + if ((out_bits & (1< -1 + bool x_min_endstop=(READ(X_MIN_PIN) != X_ENDSTOPS_INVERTING); + if(x_min_endstop && old_x_min_endstop && (current_block->steps_x > 0)) { + endstops_trigsteps[X_AXIS] = count_position[X_AXIS]; + endstop_x_hit=true; + step_events_completed = current_block->step_event_count; + } + old_x_min_endstop = x_min_endstop; + #endif + } + } + else { // +direction + WRITE(X_DIR_PIN,!INVERT_X_DIR); + count_direction[X_AXIS]=1; + CHECK_ENDSTOPS + { + #if X_MAX_PIN > -1 + bool x_max_endstop=(READ(X_MAX_PIN) != X_ENDSTOPS_INVERTING); + if(x_max_endstop && old_x_max_endstop && (current_block->steps_x > 0)){ + endstops_trigsteps[X_AXIS] = count_position[X_AXIS]; + endstop_x_hit=true; + step_events_completed = current_block->step_event_count; + } + old_x_max_endstop = x_max_endstop; + #endif + } + } + + if ((out_bits & (1< -1 + bool y_min_endstop=(READ(Y_MIN_PIN) != Y_ENDSTOPS_INVERTING); + if(y_min_endstop && old_y_min_endstop && (current_block->steps_y > 0)) { + endstops_trigsteps[Y_AXIS] = count_position[Y_AXIS]; + endstop_y_hit=true; + step_events_completed = current_block->step_event_count; + } + old_y_min_endstop = y_min_endstop; + #endif + } + } + else { // +direction + WRITE(Y_DIR_PIN,!INVERT_Y_DIR); + count_direction[Y_AXIS]=1; + CHECK_ENDSTOPS + { + #if Y_MAX_PIN > -1 + bool y_max_endstop=(READ(Y_MAX_PIN) != Y_ENDSTOPS_INVERTING); + if(y_max_endstop && old_y_max_endstop && (current_block->steps_y > 0)){ + endstops_trigsteps[Y_AXIS] = count_position[Y_AXIS]; + endstop_y_hit=true; + step_events_completed = current_block->step_event_count; + } + old_y_max_endstop = y_max_endstop; + #endif + } + } + + if ((out_bits & (1< -1 + bool z_min_endstop=(READ(Z_MIN_PIN) != Z_ENDSTOPS_INVERTING); + if(z_min_endstop && old_z_min_endstop && (current_block->steps_z > 0)) { + endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS]; + endstop_z_hit=true; + step_events_completed = current_block->step_event_count; + } + old_z_min_endstop = z_min_endstop; + #endif + } + } + else { // +direction + WRITE(Z_DIR_PIN,!INVERT_Z_DIR); + count_direction[Z_AXIS]=1; + CHECK_ENDSTOPS + { + #if Z_MAX_PIN > -1 + bool z_max_endstop=(READ(Z_MAX_PIN) != Z_ENDSTOPS_INVERTING); + if(z_max_endstop && old_z_max_endstop && (current_block->steps_z > 0)) { + endstops_trigsteps[Z_AXIS] = count_position[Z_AXIS]; + endstop_z_hit=true; + step_events_completed = current_block->step_event_count; + } + old_z_max_endstop = z_max_endstop; + #endif + } + } + + #ifndef ADVANCE + if ((out_bits & (1<steps_e; + if (counter_e > 0) { + counter_e -= current_block->step_event_count; + if ((out_bits & (1<active_extruder]--; + } + else { + e_steps[current_block->active_extruder]++; + } + } + #endif //ADVANCE + + counter_x += current_block->steps_x; + if (counter_x > 0) { + WRITE(X_STEP_PIN, HIGH); + counter_x -= current_block->step_event_count; + WRITE(X_STEP_PIN, LOW); + count_position[X_AXIS]+=count_direction[X_AXIS]; + } + + counter_y += current_block->steps_y; + if (counter_y > 0) { + WRITE(Y_STEP_PIN, HIGH); + counter_y -= current_block->step_event_count; + WRITE(Y_STEP_PIN, LOW); + count_position[Y_AXIS]+=count_direction[Y_AXIS]; + } + + counter_z += current_block->steps_z; + if (counter_z > 0) { + WRITE(Z_STEP_PIN, HIGH); + counter_z -= current_block->step_event_count; + WRITE(Z_STEP_PIN, LOW); + count_position[Z_AXIS]+=count_direction[Z_AXIS]; + } + + #ifndef ADVANCE + counter_e += current_block->steps_e; + if (counter_e > 0) { + // M571 enable, since extruder motor active + if (m571_enabled) WRITE(M571_PIN, HIGH); + // N571 disables real E drive! (ie. on laser operations) + if (!n571_enabled) { + WRITE_E_STEP(HIGH); + counter_e -= current_block->step_event_count; + WRITE_E_STEP(LOW); + } else counter_e -= current_block->step_event_count; + count_position[E_AXIS]+=count_direction[E_AXIS]; + } else { + // M571 disable, no more E_steps to do + if (m571_enabled) WRITE(M571_PIN, LOW); + + } + #endif //!ADVANCE + step_events_completed += 1; + if(step_events_completed >= current_block->step_event_count) break; + } + // Calculare new timer value + unsigned short timer; + unsigned short step_rate; + if (step_events_completed <= (unsigned long int)current_block->accelerate_until) { + + MultiU24X24toH16(acc_step_rate, acceleration_time, current_block->acceleration_rate); + acc_step_rate += current_block->initial_rate; + + // upper limit + if(acc_step_rate > current_block->nominal_rate) + acc_step_rate = current_block->nominal_rate; + + // step_rate to timer interval + timer = calc_timer(acc_step_rate); + OCR1A = timer; + acceleration_time += timer; + #ifdef ADVANCE + for(int8_t i=0; i < step_loops; i++) { + advance += advance_rate; + } + //if(advance > current_block->advance) advance = current_block->advance; + // Do E steps + advance steps + e_steps[current_block->active_extruder] += ((advance >>8) - old_advance); + old_advance = advance >>8; + + #endif + } + else if (step_events_completed > (unsigned long int)current_block->decelerate_after) { + MultiU24X24toH16(step_rate, deceleration_time, current_block->acceleration_rate); + + if(step_rate > acc_step_rate) { // Check step_rate stays positive + step_rate = current_block->final_rate; + } + else { + step_rate = acc_step_rate - step_rate; // Decelerate from aceleration end point. + } + + // lower limit + if(step_rate < current_block->final_rate) + step_rate = current_block->final_rate; + + // step_rate to timer interval + timer = calc_timer(step_rate); + OCR1A = timer; + deceleration_time += timer; + #ifdef ADVANCE + for(int8_t i=0; i < step_loops; i++) { + advance -= advance_rate; + } + if(advance < final_advance) advance = final_advance; + // Do E steps + advance steps + e_steps[current_block->active_extruder] += ((advance >>8) - old_advance); + old_advance = advance >>8; + #endif //ADVANCE + } + else { + OCR1A = OCR1A_nominal; + } + + // If current block is finished, reset pointer + if (step_events_completed >= current_block->step_event_count) { + current_block = NULL; + plan_discard_current_block(); + } + } +} + +#ifdef ADVANCE + unsigned char old_OCR0A; + // Timer interrupt for E. e_steps is set in the main routine; + // Timer 0 is shared with millies + ISR(TIMER0_COMPA_vect) + { + old_OCR0A += 52; // ~10kHz interrupt (250000 / 26 = 9615kHz) + OCR0A = old_OCR0A; + // Set E direction (Depends on E direction + advance) + for(unsigned char i=0; i<4;i++) { + if (e_steps[0] != 0) { + WRITE(E0_STEP_PIN, LOW); + if (e_steps[0] < 0) { + WRITE(E0_DIR_PIN, INVERT_E0_DIR); + e_steps[0]++; + WRITE(E0_STEP_PIN, HIGH); + } + else if (e_steps[0] > 0) { + WRITE(E0_DIR_PIN, !INVERT_E0_DIR); + e_steps[0]--; + WRITE(E0_STEP_PIN, HIGH); + } + } + #if EXTRUDERS > 1 + if (e_steps[1] != 0) { + WRITE(E1_STEP_PIN, LOW); + if (e_steps[1] < 0) { + WRITE(E1_DIR_PIN, INVERT_E1_DIR); + e_steps[1]++; + WRITE(E1_STEP_PIN, HIGH); + } + else if (e_steps[1] > 0) { + WRITE(E1_DIR_PIN, !INVERT_E1_DIR); + e_steps[1]--; + WRITE(E1_STEP_PIN, HIGH); + } + } + #endif + #if EXTRUDERS > 2 + if (e_steps[2] != 0) { + WRITE(E2_STEP_PIN, LOW); + if (e_steps[2] < 0) { + WRITE(E2_DIR_PIN, INVERT_E2_DIR); + e_steps[2]++; + WRITE(E2_STEP_PIN, HIGH); + } + else if (e_steps[2] > 0) { + WRITE(E2_DIR_PIN, !INVERT_E2_DIR); + e_steps[2]--; + WRITE(E2_STEP_PIN, HIGH); + } + } + #endif + } + } +#endif // ADVANCE + +void st_init() +{ + //Initialize Dir Pins + #if X_DIR_PIN > -1 + SET_OUTPUT(X_DIR_PIN); + #endif + #if Y_DIR_PIN > -1 + SET_OUTPUT(Y_DIR_PIN); + #endif + #if Z_DIR_PIN > -1 + SET_OUTPUT(Z_DIR_PIN); + #endif + #if E0_DIR_PIN > -1 + SET_OUTPUT(E0_DIR_PIN); + #endif + #if defined(E1_DIR_PIN) && (E1_DIR_PIN > -1) + SET_OUTPUT(E1_DIR_PIN); + #endif + #if defined(E2_DIR_PIN) && (E2_DIR_PIN > -1) + SET_OUTPUT(E2_DIR_PIN); + #endif + + //Initialize Enable Pins - steppers default to disabled. + + #if (X_ENABLE_PIN > -1) + SET_OUTPUT(X_ENABLE_PIN); + if(!X_ENABLE_ON) WRITE(X_ENABLE_PIN,HIGH); + #endif + #if (Y_ENABLE_PIN > -1) + SET_OUTPUT(Y_ENABLE_PIN); + if(!Y_ENABLE_ON) WRITE(Y_ENABLE_PIN,HIGH); + #endif + #if (Z_ENABLE_PIN > -1) + SET_OUTPUT(Z_ENABLE_PIN); + if(!Z_ENABLE_ON) WRITE(Z_ENABLE_PIN,HIGH); + #endif + #if (E0_ENABLE_PIN > -1) + SET_OUTPUT(E0_ENABLE_PIN); + if(!E_ENABLE_ON) WRITE(E0_ENABLE_PIN,HIGH); + #endif + #if defined(E1_ENABLE_PIN) && (E1_ENABLE_PIN > -1) + SET_OUTPUT(E1_ENABLE_PIN); + if(!E_ENABLE_ON) WRITE(E1_ENABLE_PIN,HIGH); + #endif + #if defined(E2_ENABLE_PIN) && (E2_ENABLE_PIN > -1) + SET_OUTPUT(E2_ENABLE_PIN); + if(!E_ENABLE_ON) WRITE(E2_ENABLE_PIN,HIGH); + #endif + + //endstops and pullups + #ifdef ENDSTOPPULLUPS + #if X_MIN_PIN > -1 + SET_INPUT(X_MIN_PIN); + WRITE(X_MIN_PIN,HIGH); + #endif + #if X_MAX_PIN > -1 + SET_INPUT(X_MAX_PIN); + WRITE(X_MAX_PIN,HIGH); + #endif + #if Y_MIN_PIN > -1 + SET_INPUT(Y_MIN_PIN); + WRITE(Y_MIN_PIN,HIGH); + #endif + #if Y_MAX_PIN > -1 + SET_INPUT(Y_MAX_PIN); + WRITE(Y_MAX_PIN,HIGH); + #endif + #if Z_MIN_PIN > -1 + SET_INPUT(Z_MIN_PIN); + WRITE(Z_MIN_PIN,HIGH); + #endif + #if Z_MAX_PIN > -1 + SET_INPUT(Z_MAX_PIN); + WRITE(Z_MAX_PIN,HIGH); + #endif + #else //ENDSTOPPULLUPS + #if X_MIN_PIN > -1 + SET_INPUT(X_MIN_PIN); + #endif + #if X_MAX_PIN > -1 + SET_INPUT(X_MAX_PIN); + #endif + #if Y_MIN_PIN > -1 + SET_INPUT(Y_MIN_PIN); + #endif + #if Y_MAX_PIN > -1 + SET_INPUT(Y_MAX_PIN); + #endif + #if Z_MIN_PIN > -1 + SET_INPUT(Z_MIN_PIN); + #endif + #if Z_MAX_PIN > -1 + SET_INPUT(Z_MAX_PIN); + #endif + #endif //ENDSTOPPULLUPS + + + //Initialize Step Pins + #if (X_STEP_PIN > -1) + SET_OUTPUT(X_STEP_PIN); + #if X_ENABLE_PIN > -1 + if(!X_ENABLE_ON) WRITE(X_ENABLE_PIN,HIGH); + #endif + #endif + #if (Y_STEP_PIN > -1) + SET_OUTPUT(Y_STEP_PIN); + #if Y_ENABLE_PIN > -1 + if(!Y_ENABLE_ON) WRITE(Y_ENABLE_PIN,HIGH); + #endif + #endif + #if (Z_STEP_PIN > -1) + SET_OUTPUT(Z_STEP_PIN); + #if Z_ENABLE_PIN > -1 + if(!Z_ENABLE_ON) WRITE(Z_ENABLE_PIN,HIGH); + #endif + #endif + #if (E0_STEP_PIN > -1) + SET_OUTPUT(E0_STEP_PIN); + #if E0_ENABLE_PIN > -1 + if(!E_ENABLE_ON) WRITE(E0_ENABLE_PIN,HIGH); + #endif + #endif + #if defined(E1_STEP_PIN) && (E1_STEP_PIN > -1) + SET_OUTPUT(E1_STEP_PIN); + #if E1_ENABLE_PIN > -1 + if(!E_ENABLE_ON) WRITE(E1_ENABLE_PIN,HIGH); + #endif + #endif + #if defined(E2_STEP_PIN) && (E2_STEP_PIN > -1) + SET_OUTPUT(E2_STEP_PIN); + #if E2_ENABLE_PIN > -1 + if(!E_ENABLE_ON) WRITE(E2_ENABLE_PIN,HIGH); + #endif + #endif + + #ifdef CONTROLLERFAN_PIN + SET_OUTPUT(CONTROLLERFAN_PIN); //Set pin used for driver cooling fan + #endif + + // M571 disable, switch off default + if (m571_enabled) WRITE(M571_PIN, LOW); + + + // waveform generation = 0100 = CTC + TCCR1B &= ~(1<