spi and i2c

Re: spi and i2c

Postby jayache80 » Mon Apr 13, 2015 9:37 pm

Hello. I am also curious about the oscillator- the datasheet for the WM8731 seems to strongly suggest there is an internal oscillator. It says "A crystal oscillator is included on board the device" and it is pictured on the block diagram, lower left.
wm8731 block diagram.png
wm8731 block diagram.png (75.73 KiB) Viewed 13722 times
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Re: spi and i2c

Postby guest » Tue Apr 14, 2015 6:55 am

the OSC they show in the diagram is just the driver circuit, not the crystal itself. you need to add a crystal to make it work, or send it a square wave from another source.
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Re: spi and i2c

Postby jayache80 » Wed Apr 15, 2015 11:00 pm

Thank you. I was confusing myself. For anyone else:

It says "For applications where it is desirable that the WM8731/L is the system clock source, then clock
generation is achieved through the use of a suitable crystal connected between the XTI/MCLK input
and XTO output pins"

which can be interpreted as: "The Wolfson chip can be the master clock if you connect a crystal to it. It has its own on-board circuitry to generate the clock based on that crystal's output"

And goes on to say "For applications where a component other than the WM8731/L will generate the reference clock, the external system can be applied directly through the XTI/MCLK input pin with no software
configuration necessary. Note that in this situation, the oscillator circuit of the WM8731/L can be
safely powered down to conserve power"

which can be interpreted as "If you have another device being the master clock, just feed that clock to the same place you would put the crystal. You don't even need the on-board clock generation circuitry anymore so you can turn it off to save power"

Thanks again.
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