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CC2564: CC2564 Modulation Questions

Eddie Borjas
Prodigy 60 points

Part Number: CC2564

I would like to know if by default the CC2564 is setup to only use GFSK modulation. When reading HCI_Read_Enhanced_Transmit_Power_Level and HCI_Read_Transmit_Power_Level I see that the max Tx Power level always matches the GFSK max power level.

We also noticed that in HCI_Read_Enhanced_Transmit_Power_Level our DQPSK and 8DPSK values always match. We've taken several thousand samples and we haven't found a case where it doesn't. Is there a rational explanation to this?

  • 0
    TI__Mastermind 29361 points

    Hi Eddie,

    Eddie Borjas said:
    I would like to know if by default the CC2564 is setup to only use GFSK modulation. When reading HCI_Read_Enhanced_Transmit_Power_Level and HCI_Read_Transmit_Power_Level I see that the max Tx Power level always matches the GFSK max power level.

    The CC256x devices use all 3 classic BT modulations GFSK, DQPSK and 8DPSK in a classic BT connection as long as the remote device supports the same modulation types. Regarding the return values of these HCI commands, could you please share the full part number of the CC256x device (e.g. CC2564CRVMT) and the Bluetooth firmware logs so I can look into this further? 

    Bluetooth Logger User's Guide : 

    Eddie Borjas said:
    We also noticed that in HCI_Read_Enhanced_Transmit_Power_Level our DQPSK and 8DPSK values always match. We've taken several thousand samples and we haven't found a case where it doesn't. Is there a rational explanation to this?

    By default, the CC256x devices have identical power level settings for both DQPSK (2-EDR) and 8DPSK (3-EDR) modulations. They can be set to different values, but I do not see a reason why one need to do so.

    Best regards,

    Vihang

  • 0 in reply to Vihang Parmar
    Prodigy 60 points

    We are using the CC2564BRVMR chip. As a follow up given the power level readings, how would we know which modulation scheme is in use?

  • 0 in reply to Eddie Borjas
    TI__Mastermind 29361 points

    Eddie,

    Eddie Borjas said:
    As a follow up given the power level readings, how would we know which modulation scheme is in use?

    During a BR/EDR connection, the CC256x and the remote Bluetooth controller exchange the supported features including the supported modulation type. Depending on this information, the 2 controllers negotiate which modulation type to use. This is according to the Bluetooth specification. I do not believe you can reliably distinguish the modulation type used in a connection just by looking at the output power level. However, you can use a Bluetooth sniffer (e.g. Frontline) to capture the air traffic of the Bluetooth connection and find out which modulation type is being used.

    If you are performing RF test like continuous TX or Packet TX for FCC/ETSI certification, you can define the modulation type in the test command and the controller will only transmit on the selected frequency with specified modulation in the test mode.

    processors.wiki.ti.com/.../CC256x_Testing_Guide

    Best regards,

    Vihang