PCM2704C: ROM DESCRIPTOR DATA MODIFICATION

Thanks, Paul for the information.

I found in the datasheet that only PCM2705C requires Pullup on DT pin (Page no 6) .

I tried everything by changing the Max power register as 0x0A and Power attribute register as 0xC0 in the External ROM sample set but still, I am not able to get the Vendor ID in my Device Manager.

Does it require any external driver in Windows OS? 

Thanks,

Nikesh

The PCM270xC does not require a specific driver.  Please clarify: You are using the PCM2704C or the PCM2705C? Only the 2704C supports the external ROM.

Can you verify the voltage on your test points (JP9 and JP12)?  On my EVM both lines are 3.3V, so I believe the pull-ups are internal.

Hi Paul,

I am using the PCM2704C which supports the ROM.

Please correct me if I am wrong. are you talking about the JP9 and JP12 jumper or Test Points?

The Voltage on JP9 jumper on self side is 3.3V as it is directly connected to VDD and I didn't find the JP12 Jumper. I referred PCM270XC EVK schematic.

I also tested the Voltage on CK(SCL) and DT(SDA) pin and its 3.3V (internally pullup).

Could you please try to Burn the External ROM Sample data on your EVM.

Thanks,

Nikesh

Hi Nikesh,

Paul will get back to you after verifying the Burn of External ROM Data.

Regards,

AK

Thanks Akhilesh,

Please let me know the results of the ROM test on your EVK.

I think this issue is somewhat like my problem,

I also checked the Data lines on the protocol analyzer and found the results as the above case.

The EEPROM is not sending the data as it needs 2x8 bit address to read/write.

Regards,

Nikesh

Hi Nikesh,

I agree, I believe that is the problem.  The EEPROM you have selected only supports 16-bit addresses, and the PCM2704C only supports 8-bit.  Can you try to use the 24AA08?

Thanks,

Paul

Hi Paul,

I tested the PCM2704C with the AT24C16 IC and I am able to change the VID and PID.

As per my testing, PCM2704C does not support the EEPROM which is having a size more than 16KB like AT24C64 (Mentioned in the Schematic of PCM2704C EVK). we can use AT24C16 or AT24C08 EEPROM.

Also All the EEPROM sample data should be in reversed order e.g. if the VID is 08 BB then it should be stored in the EEPROM as DD 10 (Reverse the bit in Binary and Convert into the Hex).

As per my requirement, I want to Display my Customized String in the Sound Control Panel so I changed the Product String in the EEPROM as mentioned in the datasheet.

But It only works in MacOS and not in Windows 10 OS when I keep the default PCM2704C VID and PID. but if I change the PID to any other Value then it also works in Windows.

I think when it Finds the Default VID and PID windows load the Default Driver for the PCM2704C and used the Default Product String which is stored in the driver file.

So I think, for Windows 10 OS we need to get Unique PID from TI. Can you please let me know the process for the same. We are using this IC in one of our Product and so we will be requiring it in bulk.

Thanks,

Nikesh

Hi Nikesh,

To my knowledge, we do not issue custom or reserved PID values for the TI vendor ID.  That being said, I do not think there is a risk if you chose a custom/random PID for your application.  I am not sure if the Default Product String is really stored in the driver file, as the driver file is generic.  It might be worth checking if you can use a customer product string with the default PID/VID on a new Windows 10 machine (that would not have connected to the PCM before) and check if it loads the default.  I suspect the Windows 10 machine has just cached the value.