TAS5705 I2C Problem

Hi, Steven,

Are you using our TAS5705EVM with your AT89S51? For now, I'm going to assume that you're not.

Are you making sure to use the correct power up sequence per page 44 of the datasheet before writing 0x00 to register 0x1B? i.e. DVDD -> !PDN = 1, !MUTE = 1 -> clocks -> !RESET = 1, with PVDD being brought up once DVDD is stable.

- Nate

Steven,

Try setting your 0x06 register to 0x00 after changing the master volume register. The datasheet says 0x06 should initialize to 0x00, but mine kept initializing to 0x3F (all channels muted).

- Nate

I tried setting 0x06 register to 0x00 after changing the master volume register,but nothing's happening.

Steven,

Are you able to read the registers or can you only write to them?

- Nate

Before writting 0x00 to 0x05 register,I can read all the register I wrote.And it seems to be the value I wrote.But after I wrote 0x00 to 0x05 register,all the register come to the default value.

For example:

I write 0x00 to 0x1B register

I read 0x1B register,then I got 11000000.

But if I write 0x00 to 0x05 register,I read 0x1B register,its value come back to the default 0x82.

Steven,

That example seems to be part or all of the problem. What is the value of 0x05 before you write 0x00 to it but after you write 0x00 to 0x1B? My 0x1B reg stays 0xC0 after I write 0x00 to 0x05.

Also, could you post a schematic of your setup?

- Nate

0x05register before writer 0x00 to 0x05 but after 0x00 to 0x1B is 0x400676.Protel Schematic.pdf.

Steven,

I have a feeling that your RESET pin is being tripped when coming out of shutdown (writing 0x00 to 0x05). If you would, monitor that pin while writing 0x00 to 0x05, and tell me what happens.

The oscillator must be trimmed after a reset, so if the RESET pin is being triggered somehow in that process, the 0x1B reg would revert back to 0x82.

- Nate

I monitored !RESET pin and it stays high.Please have a look at my schematic.Tell me if something wrong.Thank you very much.

Steven,

I went over your schematic, and everything looks fine.

How are you monitoring the !RESET pin? Remember that it's only going to be low for a number of nanoseconds before coming back up again. I don't see any other way that the oscillator reg would be reset.

Also, writing 0x00 to 0x07 corresponds to a 24db gain. This is very high. You might want to change that to 0x30 or thereabouts just for testing unless you have a REALLY low amplitude input signal.

- Nate

Thanks,Nate.I'll try.