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CC1125: pass-through mode

Part Number: CC1125
Other Parts Discussed in Thread: CC1120


Since we need to parse the PWM code, the CC1125 must be in "pass-through mode".

However, CC1125's pass-through mode will introduce the following problems:

1. The chip of the main platform needs to read GPIO continuously to obtain the transmitted signal, so it cannot sleep;

If you do not sleep, the power consumption will not reach the standard.May I ask if there is any plan to solve this problem?

2. From the datasheet,in pass-through mode,CC1125 does not detect and process the leading codes and synchronization words of GFSK encoding,

   So can we parse the GFSK-encoded data ourselves?


  • Hi Neal,

    I have assigned someone to look into this for you.

    In the mean while, can you explain what you mean by this: "From the data sheet,in pass-through mode,CC1125 does not detect and process the leading codes and synchronization words of GFSK encoding". Where in the datasheet did you find this?

  • Are you referring to serial mode or transparent mode when you talk about pass-through mode? There is nothing called pass-through mode on our devices.

    Also, I am not sure about what problems you ask to be solved. If you use the CC1125 in serial/transparent mode your MCU must read the data continuously and there is no way to have an MCU reading a pin continuously while sleeping.

    The recommended way to use the CC1125 is to use it in FIFO mode. That way the radio looks for a packet (preamble + sync)  and fills the payload in the FIFO. It then wakes up the MCU (that has been sleeping), and the MCU reads the FIFO.

    When you are not using the radio in FIFO mode your MCU must parse all incoming data .


  • Hi Siri,

    1. the pass-through mode is " Transparent Serial Mode".  In CC112x user guide(swru295e.pdf) secion 8.7.2, we can find the introduction.

    2. When the "Development kit" was set to "Transparent mode", we can observe the PWM signal(waveform) in oscilloscope.

        But we also want to decode the GFSK modulation in "transparent mode". 

        We use DKB to test GFSK in transparent mode:

        when the RX is in FIFO mode, it can decode the GFSK message from TX,

        but when the RX is in transparent mode, after TX send GFSK message, we can't observe any regular signal(waveform) from the oscilloscope which connecting with RX. 

        so we want to know, Is it possible to decode GFSK in transparent mode?

        or do we need to set some special register fields for this?

        Look forward to your reply.

  • Hi Siri,

    Is the transparent mode,

    We must use Transparent Mode because we need to parse the PWM data;

    Can we parse GFSK data in Transparent Mode?Because we need to be compatible with (simultaneously processing) PWM and GFSK data;

    External MCU cannot sleep.


  • CC112x can receive 2-GFSK in transparent mode, but not 4-GFSK.

    Below is a plot showing the CC1120 (did not have a CC1125)  in transparent mode with 38.4 kbps (using SmartRF Studio).

    Another CC1120 is used to send packets (preamable + sync + length + payload). The payload is 0x55, 0x00, 0x55, 0xFF, 0x55, 0xFF: