WM8741 in Dual differential mode and 2-wire control mode - diyAudio
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Old 1st October 2011, 05:51 PM   #1
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Default WM8741 in Dual differential mode and 2-wire control mode

Hello,

I would like to use WM8741 in dual differential mode in software control mode and I have a couple of questions how to do this.

Datasheet of WM8741 under "Pin description, software control mode" says:
-> DIFFHW (pin 6): 0 = normal operation, 1 = differential mono mode
-> MODE/LRSEL (pin 24): 0 = hardware mode, 1 = 3-wire software mode and Z = 2-wire software mode
-> CSB/SADDR/IS (pin 28): 3-wire mode: serial control interface latch, 2-wire mode: device address select

So, I would like to use WM8741 in software mode (2-wire) and dual differential, so I should configure them like this:

-> DIFFHW = 0, so normal mode
-> MODE/LRSEL = Z, so 2-wire mode
-> CSB/SADDR/IS = 0 at first WM8741 and 1 at second WM8741

To switch the WM8741 into dual differential mode, I've to write 0x05e0 to register M2. Then, write 0x0c30 to register M4 for right channel and 0x0c10 to register M4 for left channel.

Is it correct?

How can I set the input format? I would like to use IS and 32bit word length.

Thanks and kind regards,
Heinrich
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Old 1st October 2011, 06:09 PM   #2
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Old 1st October 2011, 07:08 PM   #3
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Thank you Pano.

Regards,
Heinrich
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Old 10th October 2011, 09:50 AM   #4
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Any ideas?

Regards,
Heinrich
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Old 10th October 2011, 10:38 PM   #5
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The left channel mono and right channel mono controls are in register 8. Input format in register 5. What implementation are you referring to?
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Old 12th October 2011, 02:19 PM   #6
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I would like to set 32-bit IS, so I have to write 00001011 (0x0B) into register 5.

Then into register 8:
for LEFT-DAC: 0000110 (0x06)
for RIGHT-DAC: 0001110 (0x0E)

Then into register 7: 01000100 (0x44) for 128fs (24,576MHz Master Clock) and 192kHz.

After that it should be okay or what is your opinion?

It's my owm implementation with VS1063 as decoder, then SRC8421 and after that 2xWM8741. The data is comming from a solid state disc and streamed by LPC1769 into VS1063.

Thanks and kind regards,
Heinrich
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Old 12th October 2011, 05:19 PM   #7
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A couple of things I did when I programmed the WM8741 with Arduino:

use the following addresses for the chip addresses:
0011010 (or 0x1A) I2S switch=0
0011011 (or 0x1B) I2S switch=1
Arduino adds the 8 bit for write or read depending on whether you are writing or reading.

Also the register address are 7 bit so you need to add a 1 (write) to complete the 8 bit address

So you don't add the write bit on the chip address but you need to add the write bit to the register address.

I'll have to read the datasheet to confirm the values...

VS1063? Nice. I have a 1053 from Seeedstudio and is waiting to be used... WM8741 can interface directly to the chip because it has a 16 bit mode
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Old 12th October 2011, 06:00 PM   #8
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You can see the code for WM8741/Arduino here: Code*v*0.7a H I F I D U I N O C O D E
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Old 12th October 2011, 09:35 PM   #9
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Hi,

thank you for the detailed information about WM8741.

IC addresses are always 7-bit addresses, because the fist bit (bit 0) is the direction, so reading or writing to the device. But, you know this already.

Yes, you are correct, it is possible to connect WM8741 and VS1063 directly, but it is "just" 16-bit interface. And, if I design the whole schema by myself, I want to use the best components. Sure, CS8421 is not really necessary, but hey, why not?

Thanks for the codes for WM8741.

Kind regards,
Heinrich
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Old 12th October 2011, 10:17 PM   #10
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I see.

I did have some emails with a WM8741 engineers at Wolfson and he said "it is better to let the chip do its own oversampling" (feed 44.1k) rather than oversample and then feed the dac with 192K.

Please share your results
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