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astrochart / CHART

Completely Hackable Amateur Radio Telescope
https://astrochart.github.io
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bias T option #166

Closed adampbeardsley closed 1 year ago

adampbeardsley commented 2 years ago

RTL-SDR v3 has a bias T built in. I've been able to turn it on via the command line, but as far as I can tell it shuts off when I start our data collection script. We should work it in as an option to the script, and figure out how to keep it on.

For context I was trying to do this to use this filter/amp.

adampbeardsley commented 2 years ago

@abislam123 is working on this issue now. From slack messages, he says he's been able to turn on the bias T using the eeprom method (described in link above), but when he runs gnu radio is shuts off. One thing I'm wondering: is gnu radio changing the eeprom, or just changing an active setting? We could potentially answer this by:

  1. running the eeprom command
  2. dumping the eeprom to file
  3. turning on gnu radio (which will turn off the bias t)
  4. dump the eeprom to file again
  5. compare the two eeprom files

Did the eeprom change by running gnuradio? If so... we need to figure out where gnuradio is messing with the eeprom. If not, there must be another setting somewhere.

adampbeardsley commented 2 years ago

Ok, after a whole lotta hunting around and playing with different driver installations, it ended up being a lot easier than we thought. I think the difficulty is that the documentation was written before it was supported in the main fork of the osmosdr library. But it is supported now, so the solution is easy.

If you're making a flowgraph in gnuradio-companion, all you need to do is set Device Arguments to "rtl,bias=1" in the RTL-SDR Source block: Screenshot from 2022-06-22 12-27-39

When generating the python file from there, the code simply passes that argument to the osmosdr.source() instantiation. So in my case I now have a line that looks like: self.rtlsdr_source_0 = osmosdr.source(args="numchan=" + str(1) + " " + "rtl,bias=1")

So the last thing to do to close this issue is to add this as an option to our data acquisition script. I think we should default to NOT enabling the bias-t because if you're not using a bias-t enabled amp/antenna, you can ruin your radio. The user should purposely turn this on.