3.2

March 26, 2021

ES9016K2M Datasheet

ESS TECHNOLOGY, INC. 109 Bonaventura Drive, San Jose, CA 95134, USA Tel (408) 643-

8800 • www.esstech.com

8

Programmable FIR filter

A two stage interpolating FIR design is used. The interpolating FIR filter is generated using MATLAB, and can then be

downloaded using a custom C code.

Example Source Code for Loading a Filter

// only accept 128 or 16 coefficients

// Note:

The coefficients must be quantized to 24 bits for this method!

// Note:

Stage 1 consists of 128 values (0-127 being the coefficients)

// Note:

Stage 2 consists of 16 values (0-13 being the coefficients, 14-15 are zeros)

// Note:

Stage 2 is symmetric about coefficient 13.

See the example filters for more information.

byte reg26 = (byte)(coeffs.Count == 128 ? 0 : 128);

for (int i = 0; i < coeffs.Count; i++)

{

// stage 1 contains 128 coefficients, while stage 2 contains 16 coefficients

registers.WriteRegister(26, (byte)(reg26 + i));

// write the coefficient data

registers.WriteRegister(27, (byte)(coeffs[i] & 0xff));

registers.WriteRegister(28, (byte)((coeffs[i] >> 8) & 0xff));

registers.WriteRegister(29, (byte)((coeffs[i] >> 16) & 0xff));

registers.WriteRegister(30, 0x02);

// set the write enable bit

}

// disable the write enable bit when we're done

registers.WriteRegister(30, (byte)(setEvenBit ? 0x04 : 0x00));

OSF Bypass

The oversampling FIR filter can be bypassed, sourcing data directly into the IIR filter. ESS recommends using 8 x FSR as

the input. For example, an external signal at 44.1kHz can be oversampled externally to 8 x 44.1kHz = 352.8kHz and then

applied to the serial decoder in either I2S or LJ format. The maximum sample rate that can be applied is 1.536MHz (8 x

192kHz).