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- /**
- * Marlin 3D Printer Firmware
- * Copyright (C) 2017 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
- *
- * Based on Sprinter and grbl.
- * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
- *
- * This program 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.
- *
- * This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
- *
- */
-
- /**
- * The class Servo uses the PWM class to implement its functions
- *
- * All PWMs use the same repetition rate - 20mS because that's the normal servo rate
- */
-
- /**
- * This is a hybrid system.
- *
- * The PWM1 module is used to directly control the Servo 0, 1 & 3 pins. This keeps
- * the pulse width jitter to under a microsecond.
- *
- * For all other pins the PWM1 module is used to generate interrupts. The ISR
- * routine does the actual setting/clearing of pins. The upside is that any pin can
- * have a PWM channel assigned to it. The downside is that there is more pulse width
- * jitter. The jitter depends on what else is happening in the system and what ISRs
- * prempt the PWM ISR. Writing to the SD card can add 20 microseconds to the pulse
- * width.
- */
-
- /**
- * The data structures are setup to minimize the computation done by the ISR which
- * minimizes ISR execution time. Execution times are 2.2 - 3.7 microseconds.
- *
- * Two tables are used. active_table is used by the ISR. Changes to the table are
- * are done by copying the active_table into the work_table, updating the work_table
- * and then swapping the two tables. Swapping is done by manipulating pointers.
- *
- * Immediately after the swap the ISR uses the work_table until the start of the
- * next 20mS cycle. During this transition the "work_table" is actually the table
- * that was being used before the swap. The "active_table" contains the data that
- * will start being used at the start of the next 20mS period. This keeps the pins
- * well behaved during the transition.
- *
- * The ISR's priority is set to the maximum otherwise other ISRs can cause considerable
- * jitter in the PWM high time.
- *
- * See the end of this file for details on the hardware/firmware interaction
- */
-
- #ifndef _LPC1768_PWM_H_
- #define _LPC1768_PWM_H_
-
- #include <pinmapping.h>
- #include <lpc17xx_clkpwr.h>
-
- #define LPC_PWM1_MR0 19999 // base repetition rate minus one count - 20mS
- #define LPC_PWM1_PCLKSEL0 CLKPWR_PCLKSEL_CCLK_DIV_4 // select clock divider for prescaler - defaults to 4 on power up
- #define MR0_MARGIN 200 // if channel value too close to MR0 the system locks up
-
- void LPC1768_PWM_init(void);
- bool LPC1768_PWM_attach_pin(pin_t pin, uint32_t min=1, uint32_t max=(LPC_PWM1_MR0 - (MR0_MARGIN)), uint8_t servo_index=0xFF);
- bool LPC1768_PWM_write(pin_t pin, uint32_t value);
- bool LPC1768_PWM_detach_pin(pin_t pin);
- bool useable_hardware_PWM(pin_t pin);
-
- #endif // _LPC1768_PWM_H_
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