How do I generate PWM signal from an audio input on ADSP-BF535 Blackfin?

Look at this Application Note -

EE-242: PWM and Class-D Amplifiers with ADSP-BF535 Blackfin Processors

http://www.analog.com/en/processors-dsp/blackfin/processors/application-notes/resources/index.html

- Prasanth.

Hi Prasanth,

Thanks for the example application. I have tried it out and found out that the switching frequency of the PWM is 370KHz. The switching frequency I require for my project is 40 - 120KHz. How do I change this?

Thanks

Hi

I haven't tested this code, but this should be controlled by the timer period register. The width represents the signal amplitude, and is done within the pre-fixed period time. Read the processor manual for more details on timer.

Regards

Prasanth.

Hi, thanks for the help. I am able to change the frequency by varying the the value in *pTIMER0_PERIOD_LO and *pTIMER1_PERIOD_LO registers. But I realized that if the value of the registers increases, I would need to lower the value of this statement "temp_sLeft_Channel_In = temp_sLeft_Channel_In >> 8". What is this statement for? I don't quite understand it. I did not change the value of *pTIMER0_WIDTH_LO and *pTIMER1_WIDTH_LO though.

Found under "Process Audio Data.c"

//Process PWM

temp_sLeft_Channel_In = sLeft_Channel_In + 0x7fff;

temp_sLeft_Channel_In = temp_sLeft_Channel_In >> 8;

*pTIMER1_WIDTH_LO = temp_sLeft_Channel_In;

temp_sRight_Channel_In = sRight_Channel_In + 0x7fff;

temp_sRight_Channel_In = temp_sRight_Channel_In >> 8;

*pTIMER0_WIDTH_LO = temp_sRight_Channel_In;

Thanks,

Hubert