[参考译文] TLV320AIC3268：系数加载、第2部分

到目前为止、我的代码是：

void SetLowPass(unsigned int freq)
{
	double Fs = 48000;					// Sample Frequency
	double f0 = freq;					// Corner frequency (provided input)
	double dBGain = 0;					// Gain applied to frequencies within range
	double Q = 0.707;					// Quality constant. 0.707
	double w0, alpha, sinW, cosW;		// Intermediate calculated parameters
	double b0, b1, b2, a0, a1, a2;		// Calculated BiQuad Coefficients
	double B0, B1, B2, A1, A2;			// Normalized BiQuad Coefficients
	double B0new, B1new, B2new;			// Scaled Coefficients so N0, N1, and N2 are less than 1
	double N0, N1, N2, D1, D2;			// Calculated Continuous Coefficients
	double Mx;							// Absolute Maximum Value of 3 Coefficients
	unsigned char NB = 16;				// Number of Databits of Coefficients
	unsigned char Range;
	short N0_1Dot15, N1_1Dot15, N2_1Dot15;	// N0..N2 Conversion to 1.15 Format
	short D1_1Dot15, D2_1Dot15;				// D1 and D2 Conversion to 1.15 Format

	// Calculate intermediate Parameters
	w0 = 2*PI*f0/Fs;
	cosW = cos(w0);
	sinW = sin(w0);
	alpha = sinW/(2*Q);

	// Calculate Low Pass Filter Coefficients
	b0 = pow(10,(dBGain/20))*((1 - cosW)/2);
	b1 = pow(10,(dBGain/20))*(1 - cosW);
	b2 = pow(10,(dBGain/20))*((1 - cosW)/2);
	a0 = 1 + alpha;
	a1 = -2*cosW;
	a2 = (1-alpha);

	// Normalize so that A0 = 1
	B0 = b0/a0;
	B1 = b1/(2*a0);
	B2 = b2/a0;
	A1 = a1/(-2*a0);
	A2 = a2/(-a0);

	// Scale Coefficients for Normalized largest of values is less than 1
	Mx = Maxf(B0, B1, B2);
	if (Mx > 1.0)
	{
		B0new = B0/Mx;
		B1new = B1/Mx;
		B2new = B2/Mx;
	} else
	{
		B0new = B0;
		B1new = B1;
		B2new = B2;
	}

	// Convert Scaled Continuous Coefficients to Quantized Coefficients
	Range = 2^(NB-1)-1;

	N0 = floor(B0new*Range);
	N1 = floor(B1new*Range);
	N2 = floor(B2new*Range);
	D1 = floor(A1*Range);
	D2 = floor(A2*Range);

	// Convert N0-D2 into 1.15 Format Integers (required data format TLV320AIC3268 DSP coefficients
	N0_1Dot15 = Floatto115(N0);
	N1_1Dot15 = Floatto115(N1);
	N2_1Dot15 = Floatto115(N2);
	D1_1Dot15 = Floatto115(D1);
	D2_1Dot15 = Floatto115(D2);

    // Now, upload these new coefficients into the DSP at the location of the Low Bandpass BiQuad Instance.

	// Begin by setting DSP into Adaptive Filtering for DAC (DAC won't accept the new changes otherwise)


}

顺便提一下、与 SLAA447中的样本相比、我获得了合适的低带滤波器系数。 我唯一的问题是如何知道寄存器位置。  由於我使用缴费灵来配置双二阶，我怀疑我需要留意缴费灵所说的我们应该设置参数的地方。 SLAA447指出、这些系数应采用1.15格式。 从上面的 PPS 屏幕截图可以看出、系数采用3.23格式。 PPS 是否重新计算上传的 N0、N1、N2、D1和 D2值中的 b0、B1、B2、A1、A2值？  这是我看到的吗？

由于我正在使用 DAC、是否在 TLV320AIC3268中尚未启用自适应滤波？  我是否仍需要在第8页上设置自适应滤波模式？

如果我们使用自适应滤波、是否应该没有两组缓冲器？  第二个黄油的地址是什么？

只是注意到了这种差异。  请参见下图。 一个是文档 SLAA447、另一个是 SLAS953A (TLV320AIC3268数据表)。 数据表中的传递函数使用24位3字节数据字；更像是1.23数据格式。