Re: Ettus N200 Connecting to Device

[Marcus D. Leech]

On 08/08/2024 20:48, Q W wrote:

Hi Marcus,

Thanks very much for your comments. I am sorry for sending my enquiry to the wrong mail-list. I agree with you that usrp users mailing list would be a better place to seek for help.

I am new to SDRs and this mail list system, and really appreciate your feedback. I come from the theoretical study of wireless communications, and this is my first practical project. Would you please be more specific on SPI and GPIO on N200? I reckon there won't be heavy traffic on the SPI/GPIO connection for control signals, so not sure if high data rate is necessary. Also can you please advise if there is any other interface on N200/N210 which I can use for the control purpose?

Kind regards,

Tom

    The SPI interface from the motherboard is really intended for
    communication with the internal workings of the daughtercards
      it connects to.
    
    The GPIO is normally controlled by a host-based API, but one could
    write custom FPGA code to make GPIO do things in a more
      "clocked" fashion. One could even, I suppose, bring the SPI
    signals out of the box, but that isn't a supported thing, and
      both host-side and FPGA code would likely be required to make that
    work.
    
    The N200 isn't really intended to operate without *SOME* kind of
    daughtercard(s) installed.  The motherboard itself
      doesn't really "do" RF by itself.

On Friday, 9 August 2024 at 10:28:00 am AEST, Marcus D. Leech <patchvonbraun@gmail.com> wrote:

On 08/08/2024 20:18, Q W wrote:

Hi there,

We are considering using a USRP N200 for a project, and want to figure out some technical details before placing the order. We plan to use N200 to control our own device based on the analog RF signal sent from the device.

The general structure is to have the device’s output connected to the Rx port of N200. The output signal is processed in N200 and leads to the control (digital) signals which are fed back to tune the device. We plan to use SPI/GPIO ports for the feedback channel. My question is if such SPI/GPIO ports are available on N200? Please note that our device is not a daughter board, so I am not sure if the SPI/GPIO shown on the data sheet of N200 can be used for the control purpose. 

If SPI/GPIO is not available for such control, is there any other connection interface for the control signal sent from N200? Our own device can be relatively flexible, so any connection scheme can be considered.  

Kind regards,

Tom

USRP-specific questions should probably be posted on the usrp-users mailing list, rather than here.

However.  In the N200/N210 devices, the GPIO was exposed on the daughtercards.  SPI was really only used internally,
  between the motherboard and whatever daughter card(s) were installed.

The GPIO wasn't really designed for high-speed "stuff", which is what you'd need to "bit bang" an SPI interface out of
 the GPIO pins on whatever daughtercard you're using.