// 自动扫描测试
void autoTest() {
  Serial.println("fc_set, fc_measured, gain_1kHz");

  for(int pos=10; pos<=255; pos+=10) {
    setMCP41010(pos);
    delay(100);  // 等待稳定

    // 测量fc (需要外部频率计数器)
    float fc_actual = measureCutoff();
    float gain = measureGain(1000);  // 1kHz增益

    Serial.print(calcFcFromPos(pos));
    Serial.print(",");
    Serial.print(fc_actual);
    Serial.print(",");
    Serial.println(gain);
  }
}