How to regulate the phase on pin PA9

tom321 · July 8, 2026, 12:36pm

Hi, this is generator code

#define F_TIMER   72000000
#define FREQ    9000  

#define SAMPLES ((int)sqrt(F_TIMER / FREQ))
#define T_CNT   ((F_TIMER/FREQ)/SAMPLES)

#define sin_zero     (T_CNT/2)
#define max_amp      (sin_zero-1)

#define DEBOUNCE_DELAY 100

#define DEBOUNCE_IDLE 0
#define DEBOUNCE_ACTIVE 1

#include <libmaple/dma.h>
#include <EEPROM.h>

dma_tube_config dma_cfg;

float shift = 0.0;
float current_amp_step = 0.0;

int botonState = 0;
int flag2 = 0;
int out2 = PA8;
int out3 = PA9;
int * val2 = new int[SAMPLES];
int amp = 0;
int amp_mv = 0;
int max_mv = 3300;
int cnt = 0;
int time_track = 0;
float stp = 6.2831 / SAMPLES;
int ret = 17;

timer_dev *dev2 = PIN_MAP[out2].timer_device;
uint8 cc_channel2 = PIN_MAP[out2].timer_channel;

void fun2()
{
  static uint8_t ff = 0;
  flag2++;
  digitalWrite(out3, ff = (1 - ff));
}

void timer_conf()
{
  timer_dma_set_base_addr(dev2, TIMER_DMA_BASE_CCR1);
  timer_dma_set_burst_len(dev2, 1);
  timer_dma_enable_req(dev2, cc_channel2);
  timer_set_reload(dev2, T_CNT);
  timer_set_prescaler(dev2, 0);
}

void dma_conf()
{
  dma_init(DMA1);

  /* T1C1 DMA C2 */
  dma_cfg.tube_dst = &(dev2->regs.gen->DMAR);
  dma_cfg.tube_dst_size = DMA_SIZE_32BITS;
  dma_cfg.tube_src = val2;
  dma_cfg.tube_src_size = DMA_SIZE_32BITS;

  dma_cfg.tube_nr_xfers = SAMPLES;
  dma_cfg.tube_flags = DMA_CFG_SRC_INC | DMA_CFG_CIRC | DMA_CFG_HALF_CMPLT_IE | DMA_CFG_CMPLT_IE;

  dma_cfg.tube_req_src = DMA_REQ_SRC_TIM1_CH1;
  dma_cfg.target_data = 0;

  ret = dma_tube_cfg(DMA1, DMA_CH2, &dma_cfg);
}

void dma_start()
{
  dma_attach_interrupt(DMA1, DMA_CH2, fun2);
  dma_enable(DMA1, DMA_CH2);
  timer_resume(dev2);
}

void init_wave()
{
  int i;
  for (i = 0; i < SAMPLES; i++)
  {
    val2[i] = sin_zero + amp * sin(stp * i);
  }
}

void get_wave(float current_shift)
{
  int i;
  float phase_rad = current_shift * (6.2831853 / 360.0);
  for (i = 0; i < SAMPLES; i++)
  {
    val2[i] = sin_zero + amp * sin(stp * i + phase_rad);
  }
}

void save_settings()
{
  int addr = 0;
  EEPROM.write(addr, (int16)shift);
  addr += sizeof(int16);
  EEPROM.write(addr, (int16)current_amp_step);
}

void load_settings()
{
  int addr = 0;
  int16 loaded_shift = 0;
  int16 loaded_amp_step = 500;

  EEPROM.read(addr, (uint16*)&loaded_shift);
  addr += sizeof(int16);
  EEPROM.read(addr, (uint16*)&loaded_amp_step);

  if (loaded_shift >= 0 && loaded_shift <= 360) {
    shift = (float)loaded_shift;
  } else {
    shift = 0.0;
  }

  if (loaded_amp_step >= 0 && loaded_amp_step <= 1000) {
    current_amp_step = (float)loaded_amp_step;
  } else {
    current_amp_step = 500.0;
  }
}

void setup() {
  pinMode(out2, PWM);
  pinMode(out3, OUTPUT);

  // Custom external/internal alignment pin configurations
  pinMode(PB15, INPUT_PULLUP); // Button to INCREASE AMP STEP
  pinMode(PB13, INPUT_PULLUP); // Button to DECREASE AMP STEP
  pinMode(PA15, INPUT_PULLUP); // Button to cycle Menu Cases (0, 1, 2, 3, 4)
  pinMode(PB12, INPUT_PULLUP); // LEFT (DECREASE PHASE)
  pinMode(PB14, INPUT_PULLUP); // RIGHT (INCREASE PHASE)

  Serial.begin(115200);

  timer_conf();
  dma_conf();
  dma_start();

  load_settings();

  amp = (int)((current_amp_step / 1000.0) * max_amp);
  amp_mv = (int)((current_amp_step / 1000.0) * max_mv);

  init_wave();
  get_wave(shift);
}

void loop() {
  // 1. Menu Navigation
  if (digitalRead(PA15) == 0) {
    botonState = (botonState + 1) % 5;
    delay(250); // Button click guard
  }

  // 2. State-Dependent Logic
  switch (botonState) {
    case 0: // Idle
      Serial.println("  C0  ");
      delay(100);
      break;

    case 1: // Sine Regulation
      {
        bool update_required = false;

        // Amplitude steps handling (0 to 1000 steps)
        if (digitalRead(PB15) == LOW)
        {
          if (current_amp_step < 1000.0) {
            current_amp_step++;
            update_required = true;
          }
        }
        if (digitalRead(PB13) == LOW)
        {
          if (current_amp_step > 0.0) {
            current_amp_step--;
            update_required = true;
          }
        }

        // Phase handling (0.5 degree steps with strict rollover)
        if (digitalRead(PB14) == LOW)
        {
          shift += 0.5;
          if (shift > 360.0) {
            shift = 0.0;
          }
          update_required = true;
        }
        if (digitalRead(PB12) == LOW)
        {
          shift -= 0.5;
          if (shift < 0.0) {
            shift = 360.0;
          }
          update_required = true;
        }

        // Apply changes dynamically if a button was pressed
        if (update_required) {
          amp = (int)((current_amp_step / 1000.0) * max_amp);
          amp_mv = (int)((current_amp_step / 1000.0) * max_mv);
          get_wave(shift);
        }
      }
      
      // Your requested serial monitor layout
      Serial.print("  C1 ");
      Serial.print(" | A = ");    Serial.print(amp_mv);
      Serial.print("  P = ");     Serial.print(shift, 1); 
      Serial.println("°");
      delay(80); // Controls step speed when holding down buttons
      break;

    case 2:
      Serial.println("  C2 ");
      delay(100);
      break;

    case 3:
      Serial.println("  C3 " );
      delay(100);
      break;

    case 4:
      Serial.println("  C4 spare 2");
      delay(100);
      break;
  }
}

InquisitiveMind · July 8, 2026, 12:47pm

I'd first define the reference.

Phase is always relative to another signal. Which signal should PA9 be phase-shifted against?

tom321 · July 8, 2026, 1:34pm

look at this line

tom321 · July 8, 2026, 1:38pm

The entire term \((\omega t)\) represents the angle of the wave in radians. As time t advances, the angle continuously increases, causing the sine output to oscillate smoothly between -1 and

tom321 · July 8, 2026, 1:38pm

it is this one

InquisitiveMind · July 8, 2026, 6:48pm

I understand that phase_rad is the phase angle inside the sine function. My question is different: relative to which other waveform do you want PA9 to have that phase shift? PA8? Another timer output? An external signal?

b707 · July 8, 2026, 7:00pm

Ok, and what is your issue?

tom321 · July 9, 2026, 1:24am

to make simple, currently sine wave has phase regulation compared to square wave, PA8 > PA9, now I want to regulate phase of square wave compared to sine wave PA9 > PA8,

horace · July 9, 2026, 4:36am

what microcontroller are you using?
what frequency range do you require?

tom321 · July 9, 2026, 8:11am

sec ond line in code, stm32f

b707 · July 9, 2026, 8:50am

Isn't it the same thing?
The phase is relative.

If the phase PA8 > PA9 difference is x degrees, so PA9 > PA8 difference will be 360-x

gcjr · July 9, 2026, 9:48am

what is the purpose of sin_zero? it just adds an constant offset to the amplitude. it's name implies having something to do with the value being computed or the angle?

would be better written as

val2 [i] = amp0 + amp * sin(k * i + ph0)

where k = 2 π / nSamp

cyan - no phase or amplitude offset
yellow - 70 deg phase offset
red - -2 amplitude offset

ph0 = k *deg0

gcjr · July 9, 2026, 11:21am

another thing to consider is to maintain a continuous waveform. since you generate samples in a buffer, changing the initial phase (i.e. ph0) results in a discontinuity, an abrup phase shift.

one approach for maintaining continuity while changing phase is to change the k value, the frequency by just a little over some # of samples and keeping track of the ending phase value to be used to generate the next buffer.

once at the desired phase shift, the original k value is used, or possibly some different one.

if a change in frequency is desired, the k value is changed a little with each sample until the desired frequency is reached.

your get_wave() could have arguments for how much to change k with each sample, dK and values for both k and ph0 should be maintained between calls to get_wave()

it may be easier to have a getSample() maintaining and using the values of k and ph0 which can be called any # of times to fill buffer.

here are 3 100 sample buffers. k is incremented by 0.001 for each sample in the middle (fuchsia) group and then maintained in the last (yellow) group

yes, it's an awk program

awk '
function getSamp (dK)  {
    k    += dK
    samp  = sin(k +ph0)
    ph0  += k
    return samp
}

# ------------------------------------------------
function getNsamp (N, dK)  {
    while (N--)
        printf " %6d %8.4f\n", n++, getSamp(dK)
}

# ------------------------------------------------
BEGIN {
    Pi = atan2(0, -1)

    M     = 10^6
    Ftmr  = 72 *M
    Freq  = 9000
    Nsamp = sqrt(Ftmr /Freq)

    printf "# %8d Ftmr\n", Ftmr
    printf "# %8d Freq\n", Freq
    printf "# %8d Nsamp\n", Nsamp

    printf "thickness=1.5\n"

        ph0 = 2*Pi /9
        k   = 2*Pi / 100
        printf "color = %s\n", "cyan"
        getNsamp(100, 0)
        printf "color = %s\n", "fuchsia"
        getNsamp(100, 0.001)
        printf "color = %s\n", "yellow"
        getNsamp(100, 0)

    printf "title_x k %6.2f\n", k
}' | tee tom.xgr

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How to regulate the phase on pin PA9

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