# How to regulate the phase on pin PA9

**URL:** <https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326>\
**Category:** Programming\
**Created:** [July 8, 2026, 12:36pm UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326 "2026-07-08T12:36:09Z")\
**Posts on this page:** 13\
**Page:** 1

<div class="post-metadata">

**Author:** ![tom321](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tom321/32/1126662_2.png) [@tom321](https://forum.arduino.cc/u/tom321)\
**Post date:** [July 8, 2026, 12:36pm UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/1 "2026-07-08T12:36:09Z")

</div>

Hi, this is generator code

```arduino
#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;
  }
}

```

---

<div class="post-metadata">

**Author:** ![InquisitiveMind](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/inquisitivemind/32/1272398_2.png) [@InquisitiveMind](https://forum.arduino.cc/u/InquisitiveMind)\
**Post date:** [July 8, 2026, 12:47pm UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/2 "2026-07-08T12:47:11Z")

</div>

I'd first define the reference.

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

---

<div class="post-metadata">

**Author:** ![tom321](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tom321/32/1126662_2.png) [@tom321](https://forum.arduino.cc/u/tom321)\
**Post date:** [July 8, 2026, 1:34pm UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/3 "2026-07-08T13:34:02Z")

</div>

> [@tom321](#):
>
> `val2[i] = sin_zero + amp * sin(stp * i + phase_rad);`

look at this line

---

<div class="post-metadata">

**Author:** ![tom321](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tom321/32/1126662_2.png) [@tom321](https://forum.arduino.cc/u/tom321)\
**Post date:** [July 8, 2026, 1:38pm UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/4 "2026-07-08T13:38:05Z")

</div>

> [@InquisitiveMind](#):
>
> Phase is always relative to another signal

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

---

<div class="post-metadata">

**Author:** ![tom321](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tom321/32/1126662_2.png) [@tom321](https://forum.arduino.cc/u/tom321)\
**Post date:** [July 8, 2026, 1:38pm UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/5 "2026-07-08T13:38:40Z")

</div>

> [@tom321](#):
>
> angle of the wave

it is this one

---

<div class="post-metadata">

**Author:** ![InquisitiveMind](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/inquisitivemind/32/1272398_2.png) [@InquisitiveMind](https://forum.arduino.cc/u/InquisitiveMind)\
**Post date:** [July 8, 2026, 6:48pm UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/6 "2026-07-08T18:48:54Z")

</div>

> [@tom321](#):
>
> phase\_rad

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?

---

<div class="post-metadata">

**Author:** ![b707](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/b707/32/854321_2.png) [@b707](https://forum.arduino.cc/u/b707)\
**Post date:** [July 8, 2026, 7:00pm UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/7 "2026-07-08T19:00:06Z")

</div>

> [@tom321](#):
>
> this is generator code

Ok, and what is your issue?

---

<div class="post-metadata">

**Author:** ![tom321](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tom321/32/1126662_2.png) [@tom321](https://forum.arduino.cc/u/tom321)\
**Post date:** [July 9, 2026, 1:24am UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/8 "2026-07-09T01:24:36Z")

</div>

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,

---

<div class="post-metadata">

**Author:** ![horace](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/horace/32/1014299_2.png) [@horace](https://forum.arduino.cc/u/horace)\
**Post date:** [July 9, 2026, 4:36am UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/9 "2026-07-09T04:36:43Z")

</div>

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

---

<div class="post-metadata">

**Author:** ![tom321](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/tom321/32/1126662_2.png) [@tom321](https://forum.arduino.cc/u/tom321)\
**Post date:** [July 9, 2026, 8:11am UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/10 "2026-07-09T08:11:24Z")

</div>

> [@horace](#):
>
> what frequency range do you require?

sec ond line in code, stm32f

---

<div class="post-metadata">

**Author:** ![b707](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/b707/32/854321_2.png) [@b707](https://forum.arduino.cc/u/b707)\
**Post date:** [July 9, 2026, 8:50am UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/11 "2026-07-09T08:50:53Z")

</div>

> [@tom321](#):
>
> 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

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`

---

<div class="post-metadata">

**Author:** ![gcjr](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/gcjr/32/314015_2.png) [@gcjr](https://forum.arduino.cc/u/gcjr)\
**Post date:** [July 9, 2026, 9:48am UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/12 "2026-07-09T09:48:05Z")

</div>

> [@tom321](#):
>
> `val2[i] = sin_zero + amp * sin(stp * i + phase_rad);`

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

```arduino
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

 ![image](https://europe1.discourse-cdn.com/arduino/original/4X/e/c/3/ec301df25bac57da9adf842343555836d882fb5d.png)

---

<div class="post-metadata">

**Author:** ![gcjr](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/gcjr/32/314015_2.png) [@gcjr](https://forum.arduino.cc/u/gcjr)\
**Post date:** [July 9, 2026, 11:21am UTC](https://forum.arduino.cc/t/how-to-regulate-the-phase-on-pin-pa9/1451326/13 "2026-07-09T11:21:55Z")

</div>

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

 ![image](https://europe1.discourse-cdn.com/arduino/original/4X/7/b/3/7b33239c2158999c0d90788df68fee6acbf7d3c0.png)

yes, it's an [awk](https://en.wikipedia.org/wiki/AWK) program

```arduino
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

```