Weirdness using osmocom_source in GRC
Posted: Thu Sep 17, 2015 8:46 pm
Hi,
I created a GRC flow-graph using the osmocom-source connected to a scope sink. In running this the device seems to get into a weird state with a wide I to Q dc offset. If I unplug and replug the device and then run osmocom_fft in scope mode with manual dc osffet and iq balance correction then it shows almost equal I/Q values, modulo noise. Jon on the forum suggested, in repsonse to some other issue, that the cause for this might be setting the DC offset mode and IQ balance mode to off in the osmocom-source since this overwrites the calibration settings. He suggested setting the values to "Manual" to prevent this. However, even this does not work. Every time I run the GRC flow-graph after a fresh power cycle it goes into the "weird" state. Running osmocom_fft with exactly the same arguments after this shows the same large dc offset. Repeating the power cycle and running osmocom_fft shows reasonable values. I have looked at the osmocom_fft source and checked that the source block settings are identical to that in the python file generated by the GRC flow-graph but it still doesn't work.
What could be happening ?
Thanks for any help/suggestions.
--Patrick
I created a GRC flow-graph using the osmocom-source connected to a scope sink. In running this the device seems to get into a weird state with a wide I to Q dc offset. If I unplug and replug the device and then run osmocom_fft in scope mode with manual dc osffet and iq balance correction then it shows almost equal I/Q values, modulo noise. Jon on the forum suggested, in repsonse to some other issue, that the cause for this might be setting the DC offset mode and IQ balance mode to off in the osmocom-source since this overwrites the calibration settings. He suggested setting the values to "Manual" to prevent this. However, even this does not work. Every time I run the GRC flow-graph after a fresh power cycle it goes into the "weird" state. Running osmocom_fft with exactly the same arguments after this shows the same large dc offset. Repeating the power cycle and running osmocom_fft shows reasonable values. I have looked at the osmocom_fft source and checked that the source block settings are identical to that in the python file generated by the GRC flow-graph but it still doesn't work.
What could be happening ?
Thanks for any help/suggestions.
--Patrick