[Docs/Proposal] Add physical loopback setup figures and complete loopback experiment definitions (ZCU216 & RFSoC4x2)

[fabiocalabrese]

Description

Reviewing the getting_started.md guide highlights a few missing assets and incomplete sections regarding the initial loopback workflow for both supported platforms:

1. Missing Loopback Figures (../graphics/*):

   • ../graphics/zcu216_loopback.png (ZCU216 loopback connection using daughterboards).
   • ../graphics/rfsoc4x2_loopback.png (RFSoC4x2 loopback connection).

   Proposal: Add clear hardware wiring/cabling photos or connection schematics illustrating how to physically loop the DAC output back into the ADC input.

2. Loopback Experiment Definitions & Documentation:

   • ZCU216: The DAC (DAC 228 Ch 0) and ADC (ADC 224 Ch 0) channels are defined. We should provide the reference configuration and explicit description for experiments/loopback.yaml.
   • RFSoC4x2: Several placeholders remain unfilled (DAC channel ..., ADC channel ...). The loopback experiment configuration and documentation for the RFSoC4x2 need to be completed once the active DAC/ADC tile mapping is finalized in the 4x2 firmware/overlay.

[f-riente]

Thanks @fabiocalabrese for the image placeholders. We will add the images next week.

[fabiocalabrese]

Hi @f-riente, for the loopback configuration, please use the DAC-ADC connection mentioned in getting_started.md. I recently added DAC228_0 and ADC224_0 to the example usage section.

Finally, to maintain full consistency, two experiments must be added to FIREQ-Client/yaml_experiment_configuration_examples:

Loopback for zcu216: DAC228_0 --> ADC224_0

Loopback for RFSoC4x2: DAC228_0 --> ADC224_0

@Giuseppe-La-Capra, when possible, please test the getting started procedure for both boards.