Any news on DAC streaming?

[mrmatthews]

I noticed that DAC streaming is not available yet (in OS v2.0). What is the timeline for this and can it be used simultaneously with ADC streaming?
https://stackoverflow.com/questions/764 ... t-a-signal

[redpitaya]

Hello mrmatthews,

Yes, the DAC streaming is implemented in the 2.00-23 OS version, but we decided not to document it due to the following problem.

Everything is implemented on the Red Pitaya side and it should be possible to stream data from the DDR of the Red Pitaya. The problem we encountered was with the remote streaming. The generator needs a lot of points to successfully generate a signal. Even if we are transferring data at the full 20 MBps (limitation of internal Red Pitaya pipeline) we only managed to reproduce sine waves of up to a few kHz. Consequently, this feature is currently not very useful.

Would the default signal generator suffice (so as to be used in addition to the current Streaming application)?

What frequencies and what kind of signal are you trying to stream? And what is the end goal/application of this if you can share it?
This would help us a lot to understand the problem and try to find a suitable solution.

[mrmatthews]

Thanks for the feedback. I'm glad to hear about the progress.
My intermediate goal would be addressed if the outputs could be active (sine, ~100 kHz) while using ADC streaming (to TCP). Currently the "signal generator" seems to only work when a different image is loaded, and becomes inactive when ADC streaming. This would enable most of the early stage R&D demonstrations I'm working on. Currently I'm using an external signal generator, which has a relative frequency drift as expected.

Longer term it will be nice to have a custom waveform for DAC streaming with simultaneous DAC streaming. This can be useful for various forms of remote detection (lidar, gas sensing, surface characterization) as well as two way communication R&D. This is great for early stage testing via post processing, before requiring custom FPGA images.

[mrmatthews]

I just realized there is another discussion that is closely related...
viewtopic.php?f=8&t=25265

[pavel]

If by streaming DAC you mean streaming from a remote computer to the Red Pitaya board, then the performance will not be great.

This is a known limitation of the Gigabit Ethernet interface of the Xilinx Zynq-7000 and Zynq UltraScale+ chips:

https://support.xilinx.com/s/article/66670

https://support.xilinx.com/s/article/73065

https://support.xilinx.com/s/article/71168

I would not expect much more than 100-200 Mbit/s of data throughput when samples are transferred to and from the Red Pitaya board simultaneously.

I think a more efficient approach would be a configuration with continuous playback of pre-downloaded/pre-generated DAC data from the 8-256 MB buffer using the onboard RAM. The data throughput in this configuration will be about 500-600 Mbit/s in both directions.