LMX2571: Extra clocks in the FSK I2S mode

Alex Strelbytskyy

Expert 1940 points

Part Number: LMX2571

Hello,

I'm feeding modulating data into the LMX2571 using FSK I2S mode. Since standard I2S modules provide data for two channels/slots, will be it safe to supply to the synthesizer 32 bits instead of 16? Will be generated any internal error or first 16 bits will be just discarded?

Regards,

Alex

over 4 years ago

0 Noel Fung over 4 years ago

TI__Guru* 88580 points

Hi Alex,

The I2S interface does not accept standard audio I2S format, please check datasheet section 8.1 for details.

0 Alex Strelbytskyy over 4 years ago in reply to Noel Fung

Expert 1940 points

Hi Noel,

What standard micro-controllers' peripherals the LMX2571 was design to work with using FSK I2S mode? I would like to use ST micro-controllers' SAI peripheral as a source of modulating data (it works with DMA and it allows to select sampling rate we need). I can't use SPI because it doesn't to have wide selection of sampling rates and and doesn't generate FS/CS signals when it works under DMA control..

My question is very simple: if I send 16 dummy bits first and 16 valid modulating data bits after that for the same low level of the FS signal, will be latched the second 16 bit data block without any error state on the rising edge of the FS signal? The dummy 16 bits should just go through a shift register and should be discarded.

Thanks,

Alex

0 Noel Fung over 4 years ago in reply to Alex Strelbytskyy

TI__Guru* 88580 points

Hi Alex,

I think we have verified this before, let me check the record and get back.

0 Noel Fung over 4 years ago in reply to Noel Fung

TI__Guru* 88580 points

Hi Alex,

Right, only the last 16-bit will be shifted to the register.

0 Alex Strelbytskyy over 4 years ago in reply to Noel Fung

Expert 1940 points

Thanks, I see that it works for me now.

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LMX2571: Extra clocks in the FSK I2S mode