working ADC input + FFT analysis + py logger

boards/nucleo_g474re.overlay

@@ -8,7 +8,7 @@
   leds {
     compatible = "gpio-leds";
     ld2: led_0 {
-      gpios = <&gpioa 5 GPIO_ACTIVE_HIGH>; /* LD2 -> PA5 */
+      gpios = <&gpioa 5 GPIO_ACTIVE_HIGH>; // LD2 -> PA5
       label = "LD2";
     };
   };
@@ -20,4 +20,50 @@
 
 &gpioc {
   status = "okay";
+};
+
+/* ── Audio ADC ─────────────────────────────────────────
+ *
+ * ADC1 is already enabled by the board DTS with:
+ *   - pinctrl on PA0 (ADC1_IN1) — Arduino header A0
+ *   - SYNC clock, prescaler /4 → 42.5 MHz ADC clock
+ *
+ * We just add the channel config here.
+ *
+ * Conversion time = (641 + 12.5) / 42.5 MHz = 15.4 µs
+ * Max sample rate ≈ 65 kHz — plenty for 44.1 kHz
+ * Actual 44.1 kHz rate is set by a timer in code.
+ */
+&adc1 {
+  #address-cells = <1>;
+  #size-cells = <0>;
+
+  channel@1 {
+    reg = <1>; // IN1 = PA0
+    zephyr,gain = "ADC_GAIN_1";
+    zephyr,reference = "ADC_REF_INTERNAL";
+    zephyr,acquisition-time = <ADC_ACQ_TIME(ADC_ACQ_TIME_TICKS, 641)>;
+    zephyr,resolution = <12>;
+  };
+};
+
+/* ── TIM6 — ADC sample clock ─────────────────────────
+ *
+ * Basic timer, no PWM/capture — just counting.
+ * TRGO output triggers ADC1 conversions.
+ *
+ * Timer clock = 170 MHz (APB1, no prescaler)
+ * ARR = (170,000,000 / 44,100) - 1 = 3854
+ * Actual rate = 170,000,000 / 3855 = ~44,099 Hz
+ *
+ * Trigger routing (TIM6_TRGO → ADC1) is done in code
+ * via STM32 LL/HAL — devicetree just enables the clock.
+ */
+&timers6 {
+  status = "okay";
+  st,prescaler = <0>;
+
+  counter {
+    status = "okay";
+  };
 };