/**
* 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 .
*
*/
/**
* 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 and D9 & D10 pins. This keeps
* the pulse width jitter to under a microsecond.
*
* For all other pins a timer 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
* pre-empt the PWM ISR.
*/
/**
* The data structures are set up to minimize the computation done by the ISR which
* minimizes ISR execution time. Execution times are 5-14µs depending on how full the
* ISR table is. 14uS is for a 20 element ISR table.
*
* Two tables are used. One table contains the data used by the ISR to update/control
* the PWM pins. The other is used as an aid when updating the ISR table.
*
* See the end of this file for details on the hardware/firmware interaction
*/
/**
* Directly controlled PWM pins (
* NA means not being used as a directly controlled PWM pin
*
* Re-ARM MKS Sbase
* PWM1.1 P1_18 SERVO3_PIN NA(no connection)
* PWM1.1 P2_00 NA(E0_STEP_PIN) NA(X stepper)
* PWM1.2 P1_20 SERVO0_PIN NA(no connection)
* PWM1.2 P2_01 NA(X_STEP_PIN) NA(Y stepper)
* PWM1.3 P1_21 SERVO1_PIN NA(no connection)
* PWM1.3 P2_02 NA(Y_STEP_PIN) NA(Z stepper)
* PWM1.4 P1_23 NA(SDSS(SSEL0)) SERVO0_PIN
* PWM1.4 P2_03 NA(Z_STEP_PIN) NA(E0 stepper)
* PWM1.5 P1_24 NA(X_MIN_PIN) NA(X_MIN_pin)
* PWM1.5 P2_04 RAMPS_D9_PIN FAN_PIN
* PWM1.6 P1_26 NA(Y_MIN_PIN) NA(Y_MIN_pin)
* PWM1.6 P2_05 RAMPS_D10_PIN HEATER_BED_PIN
*/
#ifdef TARGET_LPC1768
#include "../../inc/MarlinConfig.h"
#include
#include "LPC1768_PWM.h"
#include "Arduino.h"
#define NUM_ISR_PWMS 20
#define LPC_PORT_OFFSET (0x0020)
#define LPC_PIN(pin) (1UL << pin)
#define LPC_GPIO(port) ((volatile LPC_GPIO_TypeDef *)(LPC_GPIO0_BASE + LPC_PORT_OFFSET * port))
typedef struct { // holds all data needed to control/init one of the PWM channels
bool active_flag; // THIS TABLE ENTRY IS ACTIVELY TOGGLING A PIN
pin_t pin;
volatile uint32_t* set_register;
volatile uint32_t* clr_register;
uint32_t write_mask; // USED BY SET/CLEAR COMMANDS
uint32_t microseconds; // value written to MR register
uint32_t min; // lower value limit checked by WRITE routine before writing to the MR register
uint32_t max; // upper value limit checked by WRITE routine before writing to the MR register
uint8_t servo_index; // 0 - MAX_SERVO -1 : servo index, 0xFF : PWM channel
} PWM_map;
PWM_map PWM1_map_A[NUM_ISR_PWMS]; // compiler will initialize to all zeros
PWM_map PWM1_map_B[NUM_ISR_PWMS]; // compiler will initialize to all zeros
PWM_map *active_table = PWM1_map_A;
PWM_map *work_table = PWM1_map_B;
PWM_map *temp_table;
#define P1_18_PWM_channel 1 // servo 3
#define P1_20_PWM_channel 2 // servo 0
#define P1_21_PWM_channel 3 // servo 1
#define P1_23_PWM_channel 4 // servo 0 for MKS Sbase
#define P2_04_PWM_channel 5 // D9
#define P2_05_PWM_channel 6 // D10
typedef struct {
uint32_t min;
uint32_t max;
bool assigned;
} table_direct;
table_direct direct_table[6]; // compiler will initialize to all zeros
/**
* Prescale register and MR0 register values
*
* 100MHz PCLK 50MHz PCLK 25MHz PCLK 12.5MHz PCLK
* ----------------- ----------------- ----------------- -----------------
* desired prescale MR0 prescale MR0 prescale MR0 prescale MR0 resolution
* prescale register register register register register register register register in degrees
* freq value value value value value value value value
*
* 8 11.5 159,999 5.25 159,999 2.13 159,999 0.5625 159,999 0.023
* 4 24 79,999 11.5 79,999 5.25 79,999 2.125 79,999 0.045
* 2 49 39,999 24 39,999 11.5 39,999 5.25 39,999 0.090
* 1 99 19,999 49 19,999 24 19,999 11.5 19,999 0.180
* 0.5 199 9,999 99 9,999 49 9,999 24 9,999 0.360
* 0.25 399 4,999 199 4,999 99 4,999 49 4,999 0.720
* 0.125 799 2,499 399 2,499 199 2,499 99 2,499 1.440
*
* The desired prescale frequency column comes from an input in the range of 544 - 2400 microseconds
* and the desire to just shift the input left or right as needed.
*
* A resolution of 0.2 degrees seems reasonable so a prescale frequency output of 1MHz is being used.
* It also means we don't need to scale the input.
*
* The PCLK is set to 25MHz because that's the slowest one that gives whole numbers for prescale and
* MR0 registers.
*
* Final settings:
* PCLKSEL0: 0x0
* PWM1PR: 0x018 (24)
* PWM1MR0: 0x04E1F (19,999)
*
*/
void LPC1768_PWM_init(void) {
///// directly controlled PWM pins (interrupts not used for these)
#define SBIT_CNTEN 0 // PWM1 counter & pre-scaler enable/disable
#define SBIT_CNTRST 1 // reset counters to known state
#define SBIT_PWMEN 3 // 1 - PWM, 0 - timer
#define SBIT_PWMMR0R 1
#define PCPWM1 6
#define PCLK_PWM1 12
SBI(LPC_SC->PCONP, PCPWM1); // Enable PWM1 controller (enabled on power up)
LPC_SC->PCLKSEL0 &= ~(0x3 << PCLK_PWM1);
LPC_SC->PCLKSEL0 |= (LPC_PWM1_PCLKSEL0 << PCLK_PWM1);
uint32_t PR = (CLKPWR_GetPCLK(CLKPWR_PCLKSEL_PWM1) / 1000000) - 1; // Prescalar to create 1 MHz output
LPC_PWM1->MR0 = LPC_PWM1_MR0; // TC resets every 19,999 + 1 cycles - sets PWM cycle(Ton+Toff) to 20 mS
// MR0 must be set before TCR enables the PWM
LPC_PWM1->TCR = _BV(SBIT_CNTEN) | _BV(SBIT_CNTRST) | _BV(SBIT_PWMEN); // Enable counters, reset counters, set mode to PWM
CBI(LPC_PWM1->TCR, SBIT_CNTRST); // Take counters out of reset
LPC_PWM1->PR = PR;
LPC_PWM1->MCR = _BV(SBIT_PWMMR0R) | _BV(0); // Reset TC if it matches MR0, disable all interrupts except for MR0
LPC_PWM1->CTCR = 0; // Disable counter mode (enable PWM mode)
LPC_PWM1->LER = 0x07F; // Set the latch Enable Bits to load the new Match Values for MR0 - MR6
LPC_PWM1->PCR = 0; // Single edge mode for all channels, PWM1 control of outputs off
//// interrupt controlled PWM setup
LPC_SC->PCONP |= 1 << 23; // power on timer3
HAL_PWM_TIMER->PR = PR;
HAL_PWM_TIMER->MCR = 0x0B; // Interrupt on MR0 & MR1, reset on MR0
HAL_PWM_TIMER->MR0 = LPC_PWM1_MR0;
HAL_PWM_TIMER->MR1 = 0;
HAL_PWM_TIMER->TCR = _BV(0); // enable
NVIC_EnableIRQ(HAL_PWM_TIMER_IRQn);
NVIC_SetPriority(HAL_PWM_TIMER_IRQn, NVIC_EncodePriority(0, 4, 0));
}
bool ISR_table_update = false; // flag to tell the ISR that the tables need to be updated & swapped
uint8_t ISR_index = 0; // index used by ISR to skip already actioned entries
#define COPY_ACTIVE_TABLE for (uint8_t i = 0; i < NUM_ISR_PWMS ; i++) work_table[i] = active_table[i]
uint32_t first_MR1_value = LPC_PWM1_MR0 + 1;
void LPC1768_PWM_sort(void) {
for (uint8_t i = NUM_ISR_PWMS; --i;) { // (bubble) sort table by microseconds
bool didSwap = false;
PWM_map temp;
for (uint16_t j = 0; j < i; ++j) {
if (work_table[j].microseconds > work_table[j + 1].microseconds) {
temp = work_table[j + 1];
work_table[j + 1] = work_table[j];
work_table[j] = temp;
didSwap = true;
}
}
if (!didSwap) break;
}
}
bool LPC1768_PWM_attach_pin(pin_t pin, uint32_t min /* = 1 */, uint32_t max /* = (LPC_PWM1_MR0 - 1) */, uint8_t servo_index /* = 0xff */) {
pin = GET_PIN_MAP_PIN(GET_PIN_MAP_INDEX(pin & 0xFF)); // Sometimes the upper byte is garbled
//// direct control PWM code
switch(pin) {
case P1_23: // MKS Sbase Servo 0, PWM1 channel 4 (J3-8 PWM1.4)
direct_table[P1_23_PWM_channel - 1].min = min;
direct_table[P1_23_PWM_channel - 1].max = MIN(max, LPC_PWM1_MR0 - MR0_MARGIN);
direct_table[P1_23_PWM_channel - 1].assigned = true;
return true;
case P1_20: // Servo 0, PWM1 channel 2 (Pin 11 P1.20 PWM1.2)
direct_table[P1_20_PWM_channel - 1].min = min;
direct_table[P1_20_PWM_channel - 1].max = MIN(max, LPC_PWM1_MR0 - MR0_MARGIN);
direct_table[P1_20_PWM_channel - 1].assigned = true;
return true;
case P1_21: // Servo 1, PWM1 channel 3 (Pin 6 P1.21 PWM1.3)
direct_table[P1_21_PWM_channel - 1].min = min;
direct_table[P1_21_PWM_channel - 1].max = MIN(max, LPC_PWM1_MR0 - MR0_MARGIN);
direct_table[P1_21_PWM_channel - 1].assigned = true;
return true;
case P1_18: // Servo 3, PWM1 channel 1 (Pin 4 P1.18 PWM1.1)
direct_table[P1_18_PWM_channel - 1].min = min;
direct_table[P1_18_PWM_channel - 1].max = MIN(max, LPC_PWM1_MR0 - MR0_MARGIN);
direct_table[P1_18_PWM_channel - 1].assigned = true;
return true;
case P2_04: // D9 FET, PWM1 channel 5 (Pin 9 P2_04 PWM1.5)
direct_table[P2_04_PWM_channel - 1].min = min;
direct_table[P2_04_PWM_channel - 1].max = MIN(max, LPC_PWM1_MR0 - MR0_MARGIN);
direct_table[P2_04_PWM_channel - 1].assigned = true;
return true;
case P2_05: // D10 FET, PWM1 channel 6 (Pin 10 P2_05 PWM1.6)
direct_table[P2_05_PWM_channel - 1].min = min;
direct_table[P2_05_PWM_channel - 1].max = MIN(max, LPC_PWM1_MR0 - MR0_MARGIN);
direct_table[P2_05_PWM_channel - 1].assigned = true;
return true;
}
//// interrupt controlled PWM code
NVIC_DisableIRQ(HAL_PWM_TIMER_IRQn); // make it safe to update the active table
// OK to update the active table because the
// ISR doesn't use any of the changed items
if (ISR_table_update) //use work table if that's the newest
temp_table = work_table;
else
temp_table = active_table;
uint8_t slot = 0;
for (uint8_t i = 0; i < NUM_ISR_PWMS; i++) // see if already in table
if (temp_table[i].pin == pin) {
NVIC_EnableIRQ(HAL_PWM_TIMER_IRQn); // re-enable PWM interrupts
return 1;
}
for (uint8_t i = 1; (i < NUM_ISR_PWMS + 1) && !slot; i++) // find empty slot
if ( !(temp_table[i - 1].set_register)) { slot = i; break; } // any item that can't be zero when active or just attached is OK
if (!slot) {
NVIC_EnableIRQ(HAL_PWM_TIMER_IRQn); // re-enable PWM interrupts
return 0;
}
slot--; // turn it into array index
temp_table[slot].pin = pin; // init slot
temp_table[slot].set_register = &LPC_GPIO(LPC1768_PIN_PORT(pin))->FIOSET;
temp_table[slot].clr_register = &LPC_GPIO(LPC1768_PIN_PORT(pin))->FIOCLR;
temp_table[slot].write_mask = LPC_PIN(LPC1768_PIN_PIN(pin));
temp_table[slot].min = min;
temp_table[slot].max = max; // different max for ISR PWMs than for direct PWMs
temp_table[slot].servo_index = servo_index;
temp_table[slot].active_flag = false;
NVIC_EnableIRQ(HAL_PWM_TIMER_IRQn); // re-enable PWM interrupts
return 1;
}
bool LPC1768_PWM_detach_pin(pin_t pin) {
pin = GET_PIN_MAP_PIN(GET_PIN_MAP_INDEX(pin & 0xFF));
//// direct control PWM code
switch(pin) {
case P1_23: // MKS Sbase Servo 0, PWM1 channel 4 (J3-8 PWM1.4)
if (!direct_table[P1_23_PWM_channel - 1].assigned) return false;
CBI(LPC_PWM1->PCR, 8 + P1_23_PWM_channel); // disable PWM1 module control of this pin
LPC_PINCON->PINSEL3 &= ~(0x3 << 14); // return pin to general purpose I/O
direct_table[P1_23_PWM_channel - 1].assigned = false;
return true;
case P1_20: // Servo 0, PWM1 channel 2 (Pin 11 P1.20 PWM1.2)
if (!direct_table[P1_20_PWM_channel - 1].assigned) return false;
CBI(LPC_PWM1->PCR, 8 + P1_20_PWM_channel); // disable PWM1 module control of this pin
LPC_PINCON->PINSEL3 &= ~(0x3 << 8); // return pin to general purpose I/O
direct_table[P1_20_PWM_channel - 1].assigned = false;
return true;
case P1_21: // Servo 1, PWM1 channel 3 (Pin 6 P1.21 PWM1.3)
if (!direct_table[P1_21_PWM_channel - 1].assigned) return false;
CBI(LPC_PWM1->PCR, 8 + P1_21_PWM_channel); // disable PWM1 module control of this pin
LPC_PINCON->PINSEL3 &= ~(0x3 << 10); // return pin to general purpose I/O
direct_table[P1_21_PWM_channel - 1].assigned = false;
return true;
case P1_18: // Servo 3, PWM1 channel 1 (Pin 4 P1.18 PWM1.1)
if (!direct_table[P1_18_PWM_channel - 1].assigned) return false;
CBI(LPC_PWM1->PCR, 8 + P1_18_PWM_channel); // disable PWM1 module control of this pin
LPC_PINCON->PINSEL3 &= ~(0x3 << 4); // return pin to general purpose I/O
direct_table[P1_18_PWM_channel - 1].assigned = false;
return true;
case P2_04: // D9 FET, PWM1 channel 5 (Pin 9 P2_04 PWM1.5)
if (!direct_table[P2_04_PWM_channel - 1].assigned) return false;
CBI(LPC_PWM1->PCR, 8 + P2_04_PWM_channel); // disable PWM1 module control of this pin
LPC_PINCON->PINSEL4 &= ~(0x3 << 10); // return pin to general purpose I/O
direct_table[P2_04_PWM_channel - 1].assigned = false;
return true;
case P2_05: // D10 FET, PWM1 channel 6 (Pin 10 P2_05 PWM1.6)
if (!direct_table[P2_05_PWM_channel - 1].assigned) return false;
CBI(LPC_PWM1->PCR, 8 + P2_05_PWM_channel); // disable PWM1 module control of this pin
LPC_PINCON->PINSEL4 &= ~(0x3 << 4); // return pin to general purpose I/O
direct_table[P2_05_PWM_channel - 1].assigned = false;
return true;
}
//// interrupt controlled PWM code
NVIC_DisableIRQ(HAL_PWM_TIMER_IRQn);
if (ISR_table_update) {
ISR_table_update = false; // don't update yet - have another update to do
NVIC_EnableIRQ(HAL_PWM_TIMER_IRQn); // re-enable PWM interrupts
}
else {
NVIC_EnableIRQ(HAL_PWM_TIMER_IRQn); // re-enable PWM interrupts
COPY_ACTIVE_TABLE; // copy active table into work table
}
uint8_t slot = 0xFF;
for (uint8_t i = 0; i < NUM_ISR_PWMS; i++) { // find slot
if (work_table[i].pin == pin) {
slot = i;
break;
}
}
if (slot == 0xFF) // return error if pin not found
return false;
work_table[slot] = {0, 0, 0, 0, 0, 0, 0, 0, 0};
LPC1768_PWM_sort(); // sort table by microseconds
ISR_table_update = true;
return true;
}
// value is 0-20,000 microseconds (0% to 100% duty cycle)
// servo routine provides values in the 544 - 2400 range
bool LPC1768_PWM_write(pin_t pin, uint32_t value) {
pin = GET_PIN_MAP_PIN(GET_PIN_MAP_INDEX(pin & 0xFF));
//// direct control PWM code
switch(pin) {
case P1_23: // MKS Sbase Servo 0, PWM1 channel 4 (J3-8 PWM1.4)
if (!direct_table[P1_23_PWM_channel - 1].assigned) return false;
LPC_PWM1->PCR |= _BV(8 + P1_23_PWM_channel); // enable PWM1 module control of this pin
LPC_PINCON->PINSEL3 = 0x2 << 14; // must set pin function AFTER setting PCR
// load the new time value
LPC_PWM1->MR4 = MAX(MIN(value, direct_table[P1_23_PWM_channel - 1].max), direct_table[P1_23_PWM_channel - 1].min);
LPC_PWM1->LER = 0x1 << P1_23_PWM_channel; // Set the latch Enable Bit to load the new Match Value on the next MR0
return true;
case P1_20: // Servo 0, PWM1 channel 2 (Pin 11 P1.20 PWM1.2)
if (!direct_table[P1_20_PWM_channel - 1].assigned) return false;
LPC_PWM1->PCR |= _BV(8 + P1_20_PWM_channel); // enable PWM1 module control of this pin
LPC_PINCON->PINSEL3 |= 0x2 << 8; // must set pin function AFTER setting PCR
// load the new time value
LPC_PWM1->MR2 = MAX(MIN(value, direct_table[P1_20_PWM_channel - 1].max), direct_table[P1_20_PWM_channel - 1].min);
LPC_PWM1->LER = 0x1 << P1_20_PWM_channel; // Set the latch Enable Bit to load the new Match Value on the next MR0
return true;
case P1_21: // Servo 1, PWM1 channel 3 (Pin 6 P1.21 PWM1.3)
if (!direct_table[P1_21_PWM_channel - 1].assigned) return false;
LPC_PWM1->PCR |= _BV(8 + P1_21_PWM_channel); // enable PWM1 module control of this pin
LPC_PINCON->PINSEL3 |= 0x2 << 10; // must set pin function AFTER setting PCR
// load the new time value
LPC_PWM1->MR3 = MAX(MIN(value, direct_table[P1_21_PWM_channel - 1].max), direct_table[P1_21_PWM_channel - 1].min);
LPC_PWM1->LER = 0x1 << P1_21_PWM_channel; // Set the latch Enable Bit to load the new Match Value on the next MR0
return true;
case P1_18: // Servo 3, PWM1 channel 1 (Pin 4 P1.18 PWM1.1)
if (!direct_table[P1_18_PWM_channel - 1].assigned) return false;
LPC_PWM1->PCR |= _BV(8 + P1_18_PWM_channel); // enable PWM1 module control of this pin
LPC_PINCON->PINSEL3 |= 0x2 << 4; // must set pin function AFTER setting PCR
// load the new time value
LPC_PWM1->MR1 = MAX(MIN(value, direct_table[P1_18_PWM_channel - 1].max), direct_table[P1_18_PWM_channel - 1].min);
LPC_PWM1->LER = 0x1 << P1_18_PWM_channel; // Set the latch Enable Bit to load the new Match Value on the next MR0
return true;
case P2_04: // D9 FET, PWM1 channel 5 (Pin 9 P2_04 PWM1.5)
if (!direct_table[P2_04_PWM_channel - 1].assigned) return false;
LPC_PWM1->PCR |= _BV(8 + P2_04_PWM_channel); // enable PWM1 module control of this pin
LPC_PINCON->PINSEL4 |= 0x1 << 8; // must set pin function AFTER setting PCR
// load the new time value
LPC_PWM1->MR5 = MAX(MIN(value, direct_table[P2_04_PWM_channel - 1].max), direct_table[P2_04_PWM_channel - 1].min);
LPC_PWM1->LER = 0x1 << P2_04_PWM_channel; // Set the latch Enable Bit to load the new Match Value on the next MR0
return true;
case P2_05: // D10 FET, PWM1 channel 6 (Pin 10 P2_05 PWM1.6)
if (!direct_table[P2_05_PWM_channel - 1].assigned) return false;
LPC_PWM1->PCR |= _BV(8 + P2_05_PWM_channel); // enable PWM1 module control of this pin
LPC_PINCON->PINSEL4 |= 0x1 << 10; // must set pin function AFTER setting PCR
// load the new time value
LPC_PWM1->MR6 = MAX(MIN(value, direct_table[P2_05_PWM_channel - 1].max), direct_table[P2_05_PWM_channel - 1].min);
LPC_PWM1->LER = 0x1 << P2_05_PWM_channel; // Set the latch Enable Bit to load the new Match Value on the next MR0
return true;
}
//// interrupt controlled PWM code
NVIC_DisableIRQ(HAL_PWM_TIMER_IRQn);
if (!ISR_table_update) // use the most up to date table
COPY_ACTIVE_TABLE; // copy active table into work table
uint8_t slot = 0xFF;
for (uint8_t i = 0; i < NUM_ISR_PWMS; i++) // find slot
if (work_table[i].pin == pin) { slot = i; break; }
if (slot == 0xFF) { // return error if pin not found
NVIC_EnableIRQ(HAL_PWM_TIMER_IRQn);
return false;
}
work_table[slot].microseconds = MAX(MIN(value, work_table[slot].max), work_table[slot].min);;
work_table[slot].active_flag = true;
LPC1768_PWM_sort(); // sort table by microseconds
ISR_table_update = true;
NVIC_EnableIRQ(HAL_PWM_TIMER_IRQn); // re-enable PWM interrupts
return 1;
}
bool useable_hardware_PWM(pin_t pin) {
pin = GET_PIN_MAP_PIN(GET_PIN_MAP_INDEX(pin & 0xFF));
NVIC_DisableIRQ(HAL_PWM_TIMER_IRQn);
bool return_flag = false;
for (uint8_t i = 0; i < NUM_ISR_PWMS; i++) // see if it's already setup
if (active_table[i].pin == pin) return_flag = true;
for (uint8_t i = 0; i < NUM_ISR_PWMS; i++) // see if there is an empty slot
if (!active_table[i].set_register) return_flag = true;
NVIC_EnableIRQ(HAL_PWM_TIMER_IRQn); // re-enable PWM interrupts
return return_flag;
}
////////////////////////////////////////////////////////////////////////////////
#define PWM_LPC1768_ISR_SAFETY_FACTOR 5 // amount of time needed to guarantee MR1 count will be above TC
volatile bool in_PWM_isr = false;
HAL_PWM_TIMER_ISR {
bool first_active_entry = true;
uint32_t next_MR1_val;
if (in_PWM_isr) goto exit_PWM_ISR; // prevent re-entering this ISR
in_PWM_isr = true;
if (HAL_PWM_TIMER->IR & 0x01) { // MR0 interrupt
next_MR1_val = first_MR1_value; // only used if have a blank ISR table
if (ISR_table_update) { // new values have been loaded so swap tables
temp_table = active_table;
active_table = work_table;
work_table = temp_table;
ISR_table_update = false;
}
}
HAL_PWM_TIMER->IR = 0x3F; // clear all interrupts
for (uint8_t i = 0; i < NUM_ISR_PWMS; i++) {
if (active_table[i].active_flag) {
if (first_active_entry) {
first_active_entry = false;
next_MR1_val = active_table[i].microseconds;
}
if (HAL_PWM_TIMER->TC < active_table[i].microseconds) {
*active_table[i].set_register = active_table[i].write_mask; // set pin high
}
else {
*active_table[i].clr_register = active_table[i].write_mask; // set pin low
next_MR1_val = (i == NUM_ISR_PWMS -1)
? LPC_PWM1_MR0 + 1 // done with table, wait for MR0
: active_table[i + 1].microseconds; // set next MR1 interrupt?
}
}
}
if (first_active_entry) next_MR1_val = LPC_PWM1_MR0 + 1; // empty table so disable MR1 interrupt
HAL_PWM_TIMER->MR1 = MAX(next_MR1_val, HAL_PWM_TIMER->TC + PWM_LPC1768_ISR_SAFETY_FACTOR); // set next
in_PWM_isr = false;
exit_PWM_ISR:
return;
}
#endif
/////////////////////////////////////////////////////////////////
///////////////// HARDWARE FIRMWARE INTERACTION ////////////////
/////////////////////////////////////////////////////////////////
/**
* There are two distinct systems used for PWMs:
* directly controlled pins
* ISR controlled pins.
*
* The two systems are independent of each other. The use the same counter frequency so there's no
* translation needed when setting the time values. The init, attach, detach and write routines all
* start with the direct pin code which is followed by the ISR pin code.
*
* The PMW1 module handles the directly controlled pins. Each directly controlled pin is associated
* with a match register (MR1 - MR6). When the associated MR equals the module's TIMER/COUNTER (TC)
* then the pins is set to low. The MR0 register controls the repetition rate. When the TC equals
* MR0 then the TC is reset and ALL directly controlled pins are set high. The resulting pulse widths
* are almost immune to system loading and ISRs. No PWM1 interrupts are used.
*
* The ISR controlled pins use the TIMER/COUNTER, MR0 and MR1 registers from one timer. MR0 controls
* period of the controls the repetition rate. When the TC equals MR0 then the TC is reset and an
* interrupt is generated. When the TC equals MR1 then an interrupt is generated.
*
* Each interrupt does the following:
* 1) Swaps the tables if it's a MR0 interrupt and the swap flag is set. It then clears the swap flag.
* 2) Scans the entire ISR table (it's been sorted low to high time)
* a. If its the first active entry then it grabs the time as a tentative time for MR1
* b. If active and TC is less than the time then it sets the pin high
* c. If active and TC is more than the time it sets the pin high
* d. On every entry that sets a pin low it grabs the NEXT entry's time for use as the next MR1.
* This results in MR1 being set to the time in the first active entry that does NOT set a
* pin low.
* e. If it's setting the last entry's pin low then it sets MR1 to a value bigger than MR0
* f. If no value has been grabbed for the next MR1 then it's an empty table and MR1 is set to a
* value greater than MR0
*/