On 11/14/2017 02:13 PM, John Ackermann N8UR wrote:
What is the clock source for a Gnuradio "internal" source such as the
Signal Source block? If there is no hardware device connected, is the
block ultimately driven by the PC clock?
Then, if there is a hardware source (SDR) as well as an internal
source, does the hardware source provide the master clock for the
flowgraph, such that any other software-derived sources are coherent
with it? Or does a Signal Source block still get its clock from the PC?
My real question is whether it's safe to assume that a flowgraph is
entirely clocked by the samples from its hardware source, and
consequently that processing within the flowgraph (e.g., oscillator
and mixer for tuning) does not introduce potential frequency errors.
Thanks,
John
A flow is clocked by the hardware--either by samples being produced or
consumed by the hardware.
The exception is when you use a "throttle" block in the absence of any
hardware. In that case, the PC clock (very roughly) controls sample rate.
So, in the absence of overruns or underruns, the signal processing in a
flow-graph cannot introduce timing errors, unless deliberate a programmmed.
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