Richard, Thanks for the quick reply. I understand the need for a throttle. However, in my case, if the selector block selects the path holding the throttle block then the hardware does not appear to throttle which makes sense because the hardware isn't being fed data; in this case the CPU then runs wild. I am seeking confirmation that reciprocity holds in that if the throttle block is not receiving a stream of data (not in the active path), it will then have no impact and the hardware will determine the actual sample rate.
Rick On 2025-05-29 11:13, Richard Bell wrote: > Hello, > > TLDR: If you are using hardware in your flowgraph, which I think you > are, then you should not include a throttle block. Only use throttle > blocks in flowgraphs with no hardware limitations (i.e. reading from > files or generating synthetic data on the fly). > > The throttle block is intended for software only scenarios, in which > you want to limit the rate at which your CPU gets called to make > computations. The throttle block simply invokes a call to sleep to > artificially "throttle" the CPU usage. It is not related to the > contextual sample rate of the underlying stream of data. Using a > throttle block with hardware can cause unintended issues where you > can't keep up with the rate of the hardware. > > For example, I could record data to a file from a radio with a sample > rate of 1 Msps. If I play back that file and plot it in GNU Radio, I > could use a throttle with any rate I want to limit CPU usage, but the > underlying sample rate of that data will always be 1 Msps. The rate of > CPU usage and the underlying sample rate of data are not coupled. > > Richard > > > > On Thu, May 29, 2025 at 10:57 AM aardric via GNU Radio, the Free & > Open-Source Toolkit for Software Radio <discuss-gnuradio@gnu.org> wrote: > > Hi, > > Could someone please confirm my understanding that the sample > rate in > the attached flow graph will be determined by the active path of the > second (from left) selector block and NOT the throttle block (that > is, > if throttle not selected)? This would be consistent with the block > documentation for the selector block on the wiki. > > > Rick >
