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PCM1865EVM: How to get 4 channel by PCM1865EVM with USB

user5799635
Prodigy 20 points
Part Number: PCM1865EVM
Other Parts Discussed in Thread: PCM1865,

Hi ,

   I have a PCM1865 EVM card and i want record 4 channel mic with usb-i2x on windows PC .

1. Change mode to mode2:

2. Configuration clock

3.Set TDM mode with 4 channel, 16bit, 50% duty cycle.

 

After configuration , i obvioused:

1) when I2S_TX_OFFSET is 0/1 only CHANNEL_2L is transmitted.

2) Set I2S_TX_OFFSET is 16 only Channel_1R + channel_2R is transmitted.

3) Set I2S_TX_OFFSET is 32 onlu Channel_1R + Channel_2L is transmitted.

How can i get 4channel data at onetimes? 

By theway, as the datasheet said BCK Ration is fixed 256*fs ,but i read Page 0 register 0x74 the BCK Ration is always 64.

BRs,

Chao Zhou

  • 0
    TI__Guru 57800 points

    Hi, Chao,

    Welcome to E2E, Thanks for your interest in our products!

    The PCM1865 is capable of streaming four channels of data over a single bus in TDM mode or two I²S buses. However, these formats are not supported by the USB-I2X board as it does not support multi-channel operation. This is a limitation of the host USB to I²S interface, the TAS1020B. The PCM1865EVM can be used for multi-channel applications when an external host device is used, there is no way to read four channels of data via USB with the USB-I2X board.  

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 20 points

    Hi Diego,

      Thanks for your response!  So, need us to set up one host device and remove i2X-board for recording 4 channel ? How to connect host device by EVM ? we don't want to change any hardware on 1865EVM board, does PCM1865EVM's GPIO pin enough to connect with host device ?

  • 0 in reply to user5799635
    TI__Guru 57800 points

    Hi, Chao,

    Correct, you need an external host device with multi-channel digital data capabilities. In order to connect the host, you have some options. 

    If you want to control the PCM1865 via I²C with the external host, you can remove the USB-I2X board and tie the external host signals to J1 of the EVM.

    You can keep the USB-I2X for I²C control and GUI interface by connecting the external host to the test points in the EVM located below the PCM1865. However, for this you need to remove resistors R20, R21, R22 and R3 to isolate PCM1865 from the rest of the EVM I²S clocks.

    GPIOs of the PCM1865 are not relevant for this application, but the EVM has access to all of them if required by your external host device.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer