Hello,
I'm writing a Linux QT application on top of library libps2_3000.
The application is available here, if you want to check out the code:
http://code.google.com/p/qpicoscope/
I have one question (I will take as example the ps3000con.c file):
When function ps3000_get_times_and_values returns I would expect that in times array between 2 consecutives values, the time elapsed would be equal to time_interval * time_units. But seems like it is not the case. Can somebody please explain me why?
Thanks in advance!
Linux Qt frontend for Picoscope 2000/3000
Re: Linux Qt frontend for Picoscope 2000/3000
time_units is an enumeration where the value returned tells you what units the values in the times array are
(0 - femto, 1 - pico, 2, nano,..... 5 - secs)
You should not multiply times by the value returned in time_interval.
(0 - femto, 1 - pico, 2, nano,..... 5 - secs)
You should not multiply times by the value returned in time_interval.
Martyn
Technical Support Manager
Technical Support Manager
Re: Linux Qt frontend for Picoscope 2000/3000
Sorry, my question was maybe not clear enough.
I am already not using time_units as it is, but doing:
double time_multiplier = adc_multipliers(time_units);
And then after ps3000_get_times_and_values returns, trying to compute the sample times in seconds doing something like:
double time[BUFFER_SIZE] = {0};
for ( i = 0; i < no_of_samples; i++ )
{
/* get sample time in seconds */
time = i * time_interval * time_multiplier;
//time = times * time_multiplier; /* Should be equivalent, but seems like it is not? */
}
Where times is a table of double filled by ps3000_get_times_and_values returns.
My question was why (i * time_interval * time_multiplier) != (times * time_multiplier)?
Thanks in advance for your help.
I am already not using time_units as it is, but doing:
double time_multiplier = adc_multipliers(time_units);
And then after ps3000_get_times_and_values returns, trying to compute the sample times in seconds doing something like:
double time[BUFFER_SIZE] = {0};
for ( i = 0; i < no_of_samples; i++ )
{
/* get sample time in seconds */
time = i * time_interval * time_multiplier;
//time = times * time_multiplier; /* Should be equivalent, but seems like it is not? */
}
Where times is a table of double filled by ps3000_get_times_and_values returns.
My question was why (i * time_interval * time_multiplier) != (times * time_multiplier)?
Thanks in advance for your help.
Re: Linux Qt frontend for Picoscope 2000/3000
What sorts of values are you getting returned in times[] ? if you can post times[0], times[1] ..... , times[10]
Martyn
Technical Support Manager
Technical Support Manager
Re: Linux Qt frontend for Picoscope 2000/3000
I've made 2 traces (with 2 different time intervals).
Well times[0] is not equal to 0, that's the only difference... Well I suppose that's OK, because intervals are the same.
But maybe you can explain me where this initial value is coming from?
LOG 1 :
LOG 2 :
Well times[0] is not equal to 0, that's the only difference... Well I suppose that's OK, because intervals are the same.
But maybe you can explain me where this initial value is coming from?
LOG 1 :
Code: Select all
DEBUG: timebase: 11 nb_of_samples:1024 oversample:1 time_units:2 time_interval:40960 time_multiplier:1.000000e-09 nb_of_samples_in_screen:1024
DEBUG: 1024 values, overflow 0
DEBUG: (times[0] * time_multiplier): 0.000061; (0 * time_multiplier * time_interval): 0.000000
DEBUG: (times[1] * time_multiplier): 0.000102; (1 * time_multiplier * time_interval): 0.000041
DEBUG: (times[2] * time_multiplier): 0.000143; (2 * time_multiplier * time_interval): 0.000082
DEBUG: (times[3] * time_multiplier): 0.000184; (3 * time_multiplier * time_interval): 0.000123
DEBUG: (times[4] * time_multiplier): 0.000225; (4 * time_multiplier * time_interval): 0.000164
DEBUG: (times[5] * time_multiplier): 0.000266; (5 * time_multiplier * time_interval): 0.000205
DEBUG: (times[6] * time_multiplier): 0.000307; (6 * time_multiplier * time_interval): 0.000246
DEBUG: (times[7] * time_multiplier): 0.000348; (7 * time_multiplier * time_interval): 0.000287
DEBUG: (times[8] * time_multiplier): 0.000389; (8 * time_multiplier * time_interval): 0.000328
DEBUG: (times[9] * time_multiplier): 0.000430; (9 * time_multiplier * time_interval): 0.000369
DEBUG: (times[10] * time_multiplier): 0.000471; (10 * time_multiplier * time_interval): 0.000410LOG 2 :
Code: Select all
DEBUG: timebase: 16 nb_of_samples:1024 oversample:1 time_units:2 time_interval:1310720 time_multiplier:1.000000e-09 nb_of_samples_in_screen:1024
DEBUG: 1024 values, overflow 0
DEBUG: (times[0] * time_multiplier): 0.001966; (0 * time_multiplier * time_interval): 0.000000
DEBUG: (times[1] * time_multiplier): 0.003277; (1 * time_multiplier * time_interval): 0.001311
DEBUG: (times[2] * time_multiplier): 0.004588; (2 * time_multiplier * time_interval): 0.002621
DEBUG: (times[3] * time_multiplier): 0.005898; (3 * time_multiplier * time_interval): 0.003932
DEBUG: (times[4] * time_multiplier): 0.007209; (4 * time_multiplier * time_interval): 0.005243
DEBUG: (times[5] * time_multiplier): 0.008520; (5 * time_multiplier * time_interval): 0.006554
DEBUG: (times[6] * time_multiplier): 0.009830; (6 * time_multiplier * time_interval): 0.007864
DEBUG: (times[7] * time_multiplier): 0.011141; (7 * time_multiplier * time_interval): 0.009175
DEBUG: (times[8] * time_multiplier): 0.012452; (8 * time_multiplier * time_interval): 0.010486
DEBUG: (times[9] * time_multiplier): 0.013763; (9 * time_multiplier * time_interval): 0.011796Re: Linux Qt frontend for Picoscope 2000/3000
Each time is the interval between the trigger event and the corresponding sample, but as a trigger event is likely to occur between samples it is reporting exactly where between the samples this is.
Martyn
Technical Support Manager
Technical Support Manager