[Discuss-gnuradio] How to create uhd's time_spec_t from Python

[Piotr Krysik]

Hi All,

time_spec_t is a class representing time in UHD. It uses time_t (long
int) for representing full seconds and double for parts of a second.
This format of time is usable to tell USRPs when to do certain tasks. It
is also very usable for operations on time without loosing precision.

In c++ time_spec_t can be constructed from time represented by a double
(not precise if number of full seconds is large) or from time_t and
double. Both constructors are exposed by SWIG in Python.

from gnuradio import uhd
uhd.time_spec(10)
uhd.time_spec(10,0.1)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/dist-packages/gnuradio/uhd/uhd_swig.py", line
1576, in __init__
this = _uhd_swig.new_time_spec_t(*args)
NotImplementedError: Wrong number or type of arguments for overloaded
function 'new_time_spec_t'.
Possible C/C++ prototypes are:
uhd::time_spec_t::time_spec_t(double)
uhd::time_spec_t::time_spec_t(time_t,double)
uhd::time_spec_t::time_spec_t(time_t,long,double)

Somehow Python's integer is not recognized as compatible with time_t
parameter in the second constructor
(uhd::time_spec_t::time_spec_t(time_t,double) ).

My question:
Is there a way to use time_spec_t's constructor
uhd::time_spec_t::time_spec_t(time_t,double) from Python interface
exposed by GNU Radio? In my opinion there should be, otherwise why to
expose it through SWIG.

--
Best Regards,
Piotr Krysik

[Marcus Müller]

Hi Piotr,

uhd.time_spec.from_ticks(full_ticks_as_int, ticks_per_second_as_float)
does the trick for me, usually. You can make one time_spec with
from_ticks(12, 1.0f) that is exactly 12 full seconds, and then add a
second one that has 0 full_secs, and a double fractional seconds.

Personally, I'm not overly happy about the fractional part of the
time_spec being double – that means that we waste a lot of the bits of a
double on exponents that never occur, and also that we're getting
different resolutions around 1.0000001 and 1.9000001. But it's like it
is, and it, in practice, works pretty well :)

Best regards,

Marcus

Post by Piotr Krysik
Hi All,
time_spec_t is a class representing time in UHD. It uses time_t (long
int) for representing full seconds and double for parts of a second.
This format of time is usable to tell USRPs when to do certain tasks. It
is also very usable for operations on time without loosing precision.
In c++ time_spec_t can be constructed from time represented by a double
(not precise if number of full seconds is large) or from time_t and
double. Both constructors are exposed by SWIG in Python.

from gnuradio import uhd
uhd.time_spec(10)
uhd.time_spec(10,0.1)

File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/dist-packages/gnuradio/uhd/uhd_swig.py", line
1576, in __init__
this = _uhd_swig.new_time_spec_t(*args)
NotImplementedError: Wrong number or type of arguments for overloaded
function 'new_time_spec_t'.
uhd::time_spec_t::time_spec_t(double)
uhd::time_spec_t::time_spec_t(time_t,double)
uhd::time_spec_t::time_spec_t(time_t,long,double)
Somehow Python's integer is not recognized as compatible with time_t
parameter in the second constructor
(uhd::time_spec_t::time_spec_t(time_t,double) ).
Is there a way to use time_spec_t's constructor
uhd::time_spec_t::time_spec_t(time_t,double) from Python interface
exposed by GNU Radio? In my opinion there should be, otherwise why to
expose it through SWIG.
--
Best Regards,
Piotr Krysik
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