TAS5806MD: Set Biquad coefficents via I2C

Hello Severin,

Refer to this E2E post https://e2e.ti.com/support/audio-group/audio/f/audio-forum/911062/ccs-tas5825m-we-need-software-source-code-of-the-ppc3-eq-module/3367549#3367549. It's for the TAS5825 but the calclation is similar for TAS58xx devices.

Best regards,

Luis.

Hello Luis,

thanks for your reply! I will check if the fromating is the same like the one provided in the link.
In the meantime could you tell me if I need to set the BQ_WR_CTRL1 Register and if, except for the formating of the coefficients, the sequence of my programm is right?

Best regards,
Severin

Hello Luis,

I checked my formating in the code and it was not the same as the one in your provided link. I now updated the code and it looks like this:

int float_to_Q_format_int(float floating_Num, char format[]){
	int q_num = 0;

	if(strcmp(format,"1.31")==0){
			q_num = round(floating_Num*pow(2,31));
	}
	else if(strcmp(format,"2.30")==0){
			q_num = round(floating_Num*pow(2,30));
	}
	else if(strcmp(format,"5.27")==0){
			q_num = round(floating_Num*pow(2,27));
	}
	else if(strcmp(format,"9.23")==0){
			q_num = round(floating_Num*pow(2,23));
	}

    //if float number is negative convert positive integer from above into negative twos compliment 
	if (floating_Num < 0){
		q_num = abs(q_num); //Magnitude of qnum
		q_num = ~q_num; 	//bitwise inverting
		q_num += 1; 		//adding +1 for negative twos compliment
	}
	return q_num;
}

//convert the int number into 4 single bytes
uint8_t *int_to_4_bytes(int int_Num){
	uint8_t *byte_Array = malloc(4);
	byte_Array[0]= (int_Num & 0xff000000) >> 24; //msB --> index 0
	byte_Array[1]= (int_Num & 0x00ff0000) >> 16;
	byte_Array[2]= (int_Num & 0x0000ff00) >> 8;
	byte_Array[3]= (int_Num & 0x000000ff); //lsB --> index 3
	return byte_Array;
}

But still there is no effect on the output.

I calculted my BQ lowpass coefficients on this website: https://www.earlevel.com/main/2013/10/13/biquad-calculator-v2/

What could be wrong with my code?

Hello Severin,

Are you able to read back the values configured in that biquad to confirm it's configured properly?

best regards,

Luis

Hello Luis,

Yes i have read the values and they seem to be correct. Now I also tried to set the first BQ for the left channel and suddenly the output on both channels was very very low. This are my coefficients with normalization applied:

                        //calculate the coefficients like in the Process Flow suggested: {b0,b1/2,b2,a1/(-2),a2/(-1)}           
float BQ_1_values [5] = {0.0002616518014479815,0.000523303602895963/2,0.0002616518014479815,-1.9537212766076175/(-2),0.9547678838134095/(-1)};

When I set them on the right first biquad nothing happens at all, but when I set them on the left first biquad both channels only have a very low output signal. 

The Register values in decimal are:

Right 1st Biquad:
b0: 0    0    137    46
b1: 0    0    137    46
b2 :0    0    137    46
a1: 7    208    156    80
a2: 248    92    162    168

Left 1st Biquad:
b0: 0    0    137    46
b1: 0    0    137    46
b2 :0    0    137    46
a1: 7    208    156    80
a2: 248    92    162    168

Any Idea? Am I calculating the BQ coefficents wrong? Also could you give me access to the TAS5806M EVM App for PPC3?

Best regards,
Severin

Hello Severin,

May you submit the request from ti.com, then i will enable the access to App.

Dylan

Hello Dylan, 

thank you for your response, I submitted a request. But could you also tell me if the coefficients are converted right from float to 5.27 Q format or not? I am still having the same problem and I can't find any more information on the Interent.

It would be really nice if someone who managed to set the coefficents right could help me. Looking forward to any help.

Best regards,
Severin

Hello Severin, 

I provided access to the TAS5806MD software, refer to the coefficients in the equalizer tab to verify your conversion. 

best regards.

Luis

Hello Luis,

I checked the values in PPC3 now and they seem to be the same so I can't really tell why it is not working. When I do not do the pre calculation like b0, b1/2, b2, a1/(-2), a2/(-1) the amplifier outputs a white noise like signal and draws abot 3 times the current it usually does. If I set the registers with pecalculted values the output just gets very silent. 
PPC3 doesn't do the preclaculation but it is in the Process flow sheet so what should I do now?


Why does PPC3 wirte 0x18 (marked with yellow) before biquads are written?

Best regards,
Severin

Hello Severin,

Can you readback register 0x66 on Page0,Book0. Additionally can you add w 58 66 86 to your write sequence before writing to the biquad.

The 0x18 is the start of the address for that first biquad because it's a multibyte write as you can see the format of the i2c write.

best regards,

Luis