PCM5122: Designs custom PCM5122 DAC with SPI - not working

user4701813

Part Number: PCM5122

Hi dear all,

I'm trying to make this chip work: I'm trying to use the SPI interface on order to command the DAC but unfortunately is not working. When I sent command to MOSI on MISO I see only High Z.

But I not really sure if I have completely understand how send data. Let make an example. If I want to read Register 0x04 I have to send 2 bytes: 0x09 0x00.

00001001 00000000

0x04 ^- this is the read bit. Last 8 bits are zeros in order to generate proper CLK signal.

The chip is connected to a rasp pi 3 via i2s in order to provide the proper clock signal. But seems not to work as expected. Maybe is there anything I can check, to understand if I completely blown the chip or if I've made an electrical mistake?

Thanks in advantage!

over 6 years ago

0 Uttam Sahu over 6 years ago

TI__Genius 14220 points

Hi,

Welcome to E2E and thank you for your query. The responsible engineer for this part is not available at this moment due to holidays. He will get back to you soon.

Regards,
Applications Engineer, Precision DACs

0 Kevin Duke over 6 years ago in reply to Uttam Sahu

TI__Mastermind 46290 points

Hello,

Could you please provide a schematic snippet showing the PCM5122 connections as well as an oscilloscope capture of the SPI signals coming from the controller?

0 user4701813 over 6 years ago in reply to Kevin Duke

Prodigy 50 points

Unfortunately I'm not able to share now a screen with the signals. The schematic I followed is the same in the data sheet, except for MODE1 that is connected to VDD.

These days I've tried to switch to i2c, so I changed Mode1 & Mode2. I can show a capture of my logic analyser and I not sure if it is working correctly.

In the picture channel 3, 7 and 6 are connected to i2s. However no audio was available to the output

0 Kevin Duke over 6 years ago in reply to user4701813

TI__Mastermind 46290 points

Unfortunately logic analyzer images are only partially useful. We really want to see the analog waveforms with an oscilloscope so we can verify setup and hold times, look for oscillation/ringing, etc. Just because the logic analyzer is interpreting the waveforms does not necessarily guarantee that the PCM is as well.

Is this being tested on the EVM? If not, is a schematic available for your PCB design? Or, is this on some other hardware platform?

0 user4701813 over 6 years ago in reply to Kevin Duke

Prodigy 50 points

I'll provide you the correct schematic tomorrow

0 user4701813 over 6 years ago in reply to Kevin Duke

Prodigy 50 points

As promised here the schematic!

0 Kevin Duke over 6 years ago in reply to user4701813

TI__Mastermind 46290 points

Hello,

The schematic does not look to have any problems, but I would still be interested in verifying the signals as near the pins as possible, ideally with an oscilloscope. I would suggest verifying even the DC mode selection pins which you look be be controlling with the 0 ohm shunt resistors to ensure that the device is indeed configured as you intend for it to be.

0 user4701813 over 6 years ago in reply to Kevin Duke

Prodigy 50 points

I'll try to do my best to provide you the necessary information. However in my first post I was trying to understand if the data sent to SPI was well formatted. If I want to read Register 0x04 I have to send 2 bytes: 0x09 0x00, is it correct? last byte to 0x00 in order to provide the proper clock signal to the DAC?

0 Kevin Duke over 6 years ago in reply to user4701813

TI__Mastermind 46290 points

That is correct. The same process that is illustrated in Figure 69 on Page 53.

0 Paul_Frost over 6 years ago in reply to Kevin Duke

TI__Guru 53283 points

What are your I2S clock rates you are using? Have you been able to read back data? Try reading the status register (0x5E).

Thanks!

0 Paul_Frost over 6 years ago in reply to Paul_Frost

TI__Guru 53283 points

Any updates?

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PCM5122: Designs custom PCM5122 DAC with SPI - not working