/* Core/Src/waveid.c —— WaveId_Extract() */
#define WV_FLAT_FRAC      0.03f   /* |dx| <= 3% of Vpp  -> "not moving"  */
#define WV_SIG_FRAC       0.05f   /* |dx| >  5% of Vpp  -> real movement */

/* Core/Src/waveid.c —— WaveId_Extract() 中求绝对值 */
uint32_t d1 = (uint32_t)buf[k + 1U] - (uint32_t)buf[k];
/* 取绝对值, d1 是无符号数相减, 负数会回绕成很大的值,
   所以用最高位判断正负 这里不能直接用 abs(),
   因为在大值上 int 转换可能溢出 */
uint32_t a1 = (d1 & 0x80000000U) ? (0U - d1) : d1;

/* 最初用的写法 (Core/Src/waveid.c), 已废弃 */
d2 = x[k+2] - 2*x[k+1] + x[k];

/* Core/Src/waveid.c —— WaveId_Extract(), 就是绕开陷阱的关键 */
/* +/-2 baseline difference: mux-safe (both samples from same side) */
{
  int32_t d2 = (int32_t)buf[k + 2U] - (int32_t)buf[k];
  if (d2 > (int32_t)sig_thr)
  {
    nup++;                    /* 明显在上升 */
  }
  else if (d2 < -(int32_t)sig_thr)
  {
    ndn++;                    /* 明显在下降 */
  }
  else
  {
    /* 两点间基本没变化, 两个计数都不加 */
  }
}

/* Core/Src/waveid.c —— WaveId_Decide() */
static WaveId_Kind WaveId_Decide(const WaveId_Features *f, uint8_t *conf)
{
  WaveId_Kind kind;

  /* -- 1. only-rising waveform -> sawtooth ----------------------------- */
  if (f->down > WV_DOWN_T)
  {
    kind = WAVEID_SAW;
    *conf = (uint8_t)(60.0f + (f->down - WV_DOWN_T) / (1.0f - WV_DOWN_T) * 40.0f);
    return kind;
  }

  /* -- 2. parks a large share of the frame on one level -> square ------ */
  if (f->peak_share > WV_PEAK_T)
  {
    kind = WAVEID_SQUARE;
    *conf = (uint8_t)(70.0f + (f->peak_share - WV_PEAK_T) /
                             (1.0f - WV_PEAK_T) * 30.0f);
    return kind;
  }

  /* -- 3. perfectly straight ramps + filled mid-range -> triangle ------ */
  if ((f->flat > WV_FLAT_TRI_T) && (f->nlevel > (uint16_t)WV_MID_OCC_T))
  {
    kind = WAVEID_TRIANGLE;
    *conf = 90U;
    return kind;
  }

  /* -- 4. discrete plateaus leave the mid-range sparse -> staircase ---- */
  if (f->nlevel <= (uint16_t)WV_MID_OCC_T)
  {
    kind = WAVEID_STAIR;
    *conf = 85U;
    return kind;
  }

  /* -- 5. otherwise a smooth, mid-range-filling curve -> sine ---------- */
  kind = WAVEID_SINE;
  *conf = 85U;
  return kind;
}

/* Core/Src/waveid.c —— 调参常量 */
/* ！！这些阈值和 Python 模型 tools/sim_waveid.py 是同一套, 改一边必须改另一边,
      否则会出现"PC 上测得好、板子上不一样"的假象 */
#define WV_FLAT_FRAC      0.03f   /* |dx| <= 3% of Vpp  -> "not moving"  */
#define WV_SIG_FRAC       0.05f   /* |dx| >  5% of Vpp  -> real movement */
#define WV_DOWN_T         0.80f   /* down share above this -> sawtooth   */
#define WV_PEAK_T         0.30f   /* densest bucket share -> square      */
#define WV_FLAT_TRI_T     0.965f  /* near-perfect straightness -> triangle */
#define WV_MID_OCC_T      2        /* populated mid buckets -> stair test */
#define WV_NBUCKET        16       /* histogram resolution                */
#define WV_MID_LO         6        /* middle third = buckets 6..9         */
#define WV_MID_HI         10       /* 只看中间三分之一, 避开两端饱和区     */
#define WV_MIN_VPP        8U       /* Vpp < 8 码值 = 没信号(幅度归零)    */

/* Core/Src/waveid.c —— WaveId_Extract() 第三遍扫描 */
/* 把 [lo, hi] 均匀分成 16 个桶, 统计每个桶里落了多少点
   分桶时用 (buf[k]-lo)/vpp 归一化, 这一步消掉了绝对幅度,
   所以后面无论信号多大, 直方图形状都一样 */
for (k = 0U; k < WAVEID_FRAME_LEN; k++)
{
  uint32_t b = (((uint32_t)(buf[k] - lo)) * WV_NBUCKET) / (uint32_t)vpp;
  if (b >= WV_NBUCKET) { b = WV_NBUCKET - 1U; }
  occ[b]++;
}

/* Core/Src/waveid.c —— WaveId_Extract(), 中段占用统计 */
uint32_t mid_pop = 0U;
uint32_t min_pop = (uint32_t)((float)WAVEID_FRAME_LEN * WV_MID_MIN_FRAC);

for (i = WV_MID_LO; i < WV_MID_HI; i++)
{
  if (occ[i] > min_pop) { mid_pop++; }
}
f->nlevel = (uint16_t)mid_pop;   /* reused field: "populated mid levels" */

/* Core/Src/waveid.c —— WaveId_EstimateFreq() */
uint32_t mid   = (uint32_t)lo + (vpp / 2U);
uint32_t hyst  = (uint32_t)vpp / 8U;      /* noise guard            */
uint32_t hi_th = mid + hyst;
uint32_t crossings = 0U;
uint8_t  armed = 0U;

/* Core/Src/waveid.c —— WaveId_Classify() */
if (out->feat.vpp_code < WV_MIN_VPP)
{
  out->kind       = WAVEID_FLAT;
  out->name       = WaveId_Name(WAVEID_FLAT);
  out->confidence = 100U;
  return;
}

/* Core/Src/app.c —— vote_push() */
static WaveId_Kind vote_push(WaveId_Kind k)
{
  uint8_t i;
  uint8_t best = 0U;
  WaveId_Kind best_kind = WAVEID_UNKNOWN;

  if ((unsigned)k < 8U)
  {
    s_votes[k]++;
  }
  s_vote_fill++;

  if (s_vote_fill < APP_VOTE_FRAMES)
  {
    /* Not enough evidence yet: report the newest frame directly. */
    return k;
  }

  for (i = 0U; i < 8U; i++)
  {
    if (s_votes[i] > best)
    {
      best = s_votes[i];
      best_kind = (WaveId_Kind)i;
    }
  }
  ...
  /* Slide the window: halve every count so the display can follow a
     waveform change promptly instead of lagging for several frames. */
  for (i = 0U; i < 8U; i++)
  {
    s_votes[i] = (uint8_t)((s_votes[i] + 1U) >> 1);
  }
  s_vote_fill = 1U;
  if ((unsigned)best_kind < 8U)
  {
    s_votes[(unsigned)best_kind]++;
  }

  return best_kind;
}

/* Core/Src/oled_ui.c —— plot_waveform() */
for (x = 0U; x < UI_WIDTH; x++)
{
  uint32_t idx = ((uint32_t)x * WAVEID_FRAME_LEN) / UI_WIDTH;
  uint16_t v;
  uint16_t y;

  if (idx >= WAVEID_FRAME_LEN) { idx = WAVEID_FRAME_LEN - 1U; }
  v = frame[idx];

  /* map [lo, hi] to [UI_PLOT_Y1, UI_PLOT_Y0] (y grows downward) */
  y = (uint16_t)(UI_PLOT_Y1 -
                 (uint16_t)(((uint32_t)(v - lo) * plot_h) / span));

  if (have_prev)
  {
    /* join successive columns so steep edges stay connected */
    OLED_DrawLine((uint8_t)(x - 1U), (uint8_t)prev_y, x, (uint8_t)y, 1);
  }
  else
  {
    OLED_DrawPoint(x, (uint8_t)y, 1);
    have_prev = 1U;
  }
  prev_y = y;
}

/* Core/Src/app.c —— 刷新节流 */
#define APP_REDRAW_MS        60U    /* OLED refresh period (~16 fps)      */

/* Core/Src/app.c —— app_process_frame() 中的重绘判断 */
if (((now - s_last_redraw) >= APP_REDRAW_MS) || (s_ui_dirty != 0U))
{
  s_last_redraw = now;
  ...
  s_ui_dirty = 0U;
}

/* Core/Src/adc.c —— MspInit 里必须手动加的两行 */
/* ★ ADC1 global interrupt: MUST be enabled.
   HAL_ADC_Start_DMA() turns on the overrun interrupt (ADC_IT_OVR); on F4 an
   uncleared OVR flag stops the ADC from issuing DMA requests forever, which
   shows up as "the display freezes until you press reset".
   ADC_IRQHandler() lives in stm32f4xx_it.c and clears it. */
HAL_NVIC_SetPriority(ADC_IRQn, 1, 0);
HAL_NVIC_EnableIRQ(ADC_IRQn);

/* Core/Src/tim.c —— MX_TIM2_Init() 末尾的说明 */
/* NOTE: TIM2 is configured as a pure time-base.  It only needs to raise
   TRGO for ADC1; no output pin is required, so PA0 is NOT claimed.  The
   inherited StateMachine setup configured TIM2 as PWM on CH1, which called
   HAL_TIM_MspPostInit() and drove PA0 as TIM2_CH1 for no reason. */