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🐛 Fix FastPWM calculations (MarlinFirmware#25343)
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Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>
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@ellensp @thinkyhead
2 people authored and Tracy Spiva committed May 25, 2023
1 parent 936eccb commit fb7c999
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Showing 3 changed files with 40 additions and 25 deletions.
27 changes: 22 additions & 5 deletions Marlin/src/HAL/AVR/fast_pwm.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,10 @@

#include "../../inc/MarlinConfig.h"

//#define DEBUG_AVR_FAST_PWM
#define DEBUG_OUT ENABLED(DEBUG_AVR_FAST_PWM)
#include "../../core/debug_out.h"

struct Timer {
volatile uint8_t* TCCRnQ[3]; // max 3 TCCR registers per timer
volatile uint16_t* OCRnQ[3]; // max 3 OCR registers per timer
Expand Down Expand Up @@ -108,36 +112,45 @@ const Timer get_pwm_timer(const pin_t pin) {
}

void MarlinHAL::set_pwm_frequency(const pin_t pin, const uint16_t f_desired) {
DEBUG_ECHOLNPGM("set_pwm_frequency(pin=", pin, ", freq=", f_desired, ")");
const Timer timer = get_pwm_timer(pin);
if (timer.isProtected || !timer.isPWM) return; // Don't proceed if protected timer or not recognized

const bool is_timer2 = timer.n == 2;
const uint16_t maxtop = is_timer2 ? 0xFF : 0xFFFF;

DEBUG_ECHOLNPGM("maxtop=", maxtop);

uint16_t res = 0xFF; // resolution (TOP value)
uint8_t j = CS_NONE; // prescaler index
uint8_t wgm = WGM_PWM_PC_8; // waveform generation mode

// Calculating the prescaler and resolution to use to achieve closest frequency
if (f_desired != 0) {
constexpr uint16_t prescaler[] = { 1, 8, (32), 64, (128), 256, 1024 }; // (*) are Timer 2 only
uint16_t f = (F_CPU) / (2 * 1024 * maxtop) + 1; // Start with the lowest non-zero frequency achievable (1 or 31)
uint16_t f = (F_CPU) / (uint32_t(maxtop) << 11) + 1; // Start with the lowest non-zero frequency achievable (for 16MHz, 1 or 31)

DEBUG_ECHOLNPGM("f=", f);
DEBUG_ECHOLNPGM("(prescaler loop)");
LOOP_L_N(i, COUNT(prescaler)) { // Loop through all prescaler values
const uint16_t p = prescaler[i];
const uint32_t p = prescaler[i]; // Extend to 32 bits for calculations
DEBUG_ECHOLNPGM("prescaler[", i, "]=", p);
uint16_t res_fast_temp, res_pc_temp;
if (is_timer2) {
#if ENABLED(USE_OCR2A_AS_TOP) // No resolution calculation for TIMER2 unless enabled USE_OCR2A_AS_TOP
const uint16_t rft = (F_CPU) / (p * f_desired);
res_fast_temp = rft - 1;
res_pc_temp = rft / 2;
DEBUG_ECHOLNPGM("(Timer2) res_fast_temp=", res_fast_temp, " res_pc_temp=", res_pc_temp);
#else
res_fast_temp = res_pc_temp = maxtop;
DEBUG_ECHOLNPGM("(Timer2) res_fast_temp=", maxtop, " res_pc_temp=", maxtop);
#endif
}
else {
if (p == 32 || p == 128) continue; // Skip TIMER2 specific prescalers when not TIMER2
const uint16_t rft = (F_CPU) / (p * f_desired);
DEBUG_ECHOLNPGM("(Not Timer 2) F_CPU=" STRINGIFY(F_CPU), " prescaler=", p, " f_desired=", f_desired);
res_fast_temp = rft - 1;
res_pc_temp = rft / 2;
}
Expand All @@ -147,23 +160,27 @@ void MarlinHAL::set_pwm_frequency(const pin_t pin, const uint16_t f_desired) {

// Calculate frequencies of test prescaler and resolution values
const uint16_t f_fast_temp = (F_CPU) / (p * (1 + res_fast_temp)),
f_pc_temp = (F_CPU) / (2 * p * res_pc_temp);
const int f_diff = _MAX(f, f_desired) - _MIN(f, f_desired),
f_pc_temp = (F_CPU) / ((p * res_pc_temp) << 1),
f_diff = _MAX(f, f_desired) - _MIN(f, f_desired),
f_fast_diff = _MAX(f_fast_temp, f_desired) - _MIN(f_fast_temp, f_desired),
f_pc_diff = _MAX(f_pc_temp, f_desired) - _MIN(f_pc_temp, f_desired);

DEBUG_ECHOLNPGM("f_fast_temp=", f_fast_temp, " f_pc_temp=", f_pc_temp, " f_diff=", f_diff, " f_fast_diff=", f_fast_diff, " f_pc_diff=", f_pc_diff);

if (f_fast_diff < f_diff && f_fast_diff <= f_pc_diff) { // FAST values are closest to desired f
// Set the Wave Generation Mode to FAST PWM
wgm = is_timer2 ? uint8_t(TERN(USE_OCR2A_AS_TOP, WGM2_FAST_PWM_OCR2A, WGM2_FAST_PWM)) : uint8_t(WGM_FAST_PWM_ICRn);
// Remember this combination
f = f_fast_temp; res = res_fast_temp; j = i + 1;
DEBUG_ECHOLNPGM("(FAST) updated f=", f);
}
else if (f_pc_diff < f_diff) { // PHASE CORRECT values are closes to desired f
// Set the Wave Generation Mode to PWM PHASE CORRECT
wgm = is_timer2 ? uint8_t(TERN(USE_OCR2A_AS_TOP, WGM2_PWM_PC_OCR2A, WGM2_PWM_PC)) : uint8_t(WGM_PWM_PC_ICRn);
f = f_pc_temp; res = res_pc_temp; j = i + 1;
DEBUG_ECHOLNPGM("(PHASE) updated f=", f);
}
}
} // prescaler loop
}

_SET_WGMnQ(timer, wgm);
Expand Down
34 changes: 16 additions & 18 deletions Marlin/src/HAL/ESP32/HAL.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -342,16 +342,16 @@ void MarlinHAL::set_pwm_duty(const pin_t pin, const uint16_t v, const uint16_t v
}
else
pindata.pwm_duty_ticks = duty; // PWM duty count = # of 4µs ticks per full PWM cycle

return;
}
else
#endif
{
const int8_t cid = get_pwm_channel(pin, PWM_FREQUENCY, PWM_RESOLUTION);
if (cid >= 0) {
const uint32_t duty = map(invert ? v_size - v : v, 0, v_size, 0, _BV(PWM_RESOLUTION)-1);
ledcWrite(cid, duty);
}
}

const int8_t cid = get_pwm_channel(pin, PWM_FREQUENCY, PWM_RESOLUTION);
if (cid >= 0) {
const uint32_t duty = map(invert ? v_size - v : v, 0, v_size, 0, _BV(PWM_RESOLUTION)-1);
ledcWrite(cid, duty);
}
}

int8_t MarlinHAL::set_pwm_frequency(const pin_t pin, const uint32_t f_desired) {
Expand All @@ -360,17 +360,15 @@ int8_t MarlinHAL::set_pwm_frequency(const pin_t pin, const uint32_t f_desired) {
pwm_pin_data[pin & 0x7F].pwm_cycle_ticks = 1000000UL / f_desired / 4; // # of 4µs ticks per full PWM cycle
return 0;
}
else
#endif
{
const int8_t cid = channel_for_pin(pin);
if (cid >= 0) {
if (f_desired == ledcReadFreq(cid)) return cid; // no freq change
ledcDetachPin(chan_pin[cid]);
chan_pin[cid] = 0; // remove old freq channel
}
return get_pwm_channel(pin, f_desired, PWM_RESOLUTION); // try for new one
}

const int8_t cid = channel_for_pin(pin);
if (cid >= 0) {
if (f_desired == ledcReadFreq(cid)) return cid; // no freq change
ledcDetachPin(chan_pin[cid]);
chan_pin[cid] = 0; // remove old freq channel
}
return get_pwm_channel(pin, f_desired, PWM_RESOLUTION); // try for new one
}

// use hardware PWM if avail, if not then ISR
Expand Down
4 changes: 2 additions & 2 deletions Marlin/src/HAL/STM32F1/fast_pwm.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@ inline uint8_t timer_and_index_for_pin(const pin_t pin, timer_dev **timer_ptr) {
void MarlinHAL::set_pwm_duty(const pin_t pin, const uint16_t v, const uint16_t v_size/*=255*/, const bool invert/*=false*/) {
const uint16_t duty = invert ? v_size - v : v;
if (PWM_PIN(pin)) {
timer_dev *timer; UNUSED(timer);
timer_dev *timer;
if (timer_freq[timer_and_index_for_pin(pin, &timer)] == 0)
set_pwm_frequency(pin, PWM_FREQUENCY);
const uint8_t channel = PIN_MAP[pin].timer_channel;
Expand All @@ -55,7 +55,7 @@ void MarlinHAL::set_pwm_duty(const pin_t pin, const uint16_t v, const uint16_t v
void MarlinHAL::set_pwm_frequency(const pin_t pin, const uint16_t f_desired) {
if (!PWM_PIN(pin)) return; // Don't proceed if no hardware timer

timer_dev *timer; UNUSED(timer);
timer_dev *timer;
timer_freq[timer_and_index_for_pin(pin, &timer)] = f_desired;

// Protect used timers
Expand Down

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