Re: [Discuss-gnuradio] Enveloping a transmit amplifier

On Wed, Aug 19, 2015 at 2:44 PM, devin kelly <address@hidden> wrote:

I tried this out and I'm having some problems. I'm on GR 3.7.8 and UHD 3.8.5, both the newest as far as I know.

What I did was make a flowgraph with a signal generator source and a UHD sink in GRC. It works before I made any modifications. There are a few lines in top_block.py that set the sample rate, antenna, etc. At the end of them I added this:

self.uhd_usrp_sink_0.set_gpio_attr("TXA", "ATR_TX", 1, 0x10, 0)

It should set pin 4 high whenever I transmit (right?). I run my flowgraph and get this traceback:

Traceback (most recent call last):
File "top_block.py", line 76, in <module>
tb = top_block()
File "top_block.py", line 55, in __init__
self.uhd_usrp_sink_0.set_gpio_attr("TXA", "ATR_TX", 1, 0x10, 0)
File "/usr/local/lib64/python2.7/site-packages/gnuradio/uhd/uhd_swig.py", line 4539, in set_gpio_attr
return _uhd_swig.usrp_sink_sptr_set_gpio_attr(self, bank, attr, value, mask, mboard)
RuntimeError: LookupError: Path not found in tree: /mboards/0/dboards/A/iface

I know I'm using the right banks because I can do this command:

$ python -c 'from gnuradio import uhd; usrp = uhd.multi_usrp_sink("serial=<removed>", uhd.io_type.COMPLEX_FLOAT32, 1); print usrp.get_gpio_banks(0)'

and get

('RXA', 'TXA')

I also run this command:

uhd_usrp_probe --args='serial=<removed>' --tree | grep -i iface

and get nothing. Without piping into grep I get 177 lines that all seem to make sense to me.

Is that command I'm using correct or is there some other issue?

Thanks,
Devin
On Wed, Aug 19, 2015 at 8:09 AM, devin kelly <address@hidden> wrote:
Marcus,

Thanks for the advice, this seems to do exactly what I'm looking for. My only question is that I've been under the impression that the UHD doesn't yet support GPIO for the B210. I did recently upgrade to 3.8.5 though so maybe things have changed?

Devin
On Wed, Aug 19, 2015 at 5:43 AM, Marcus Müller <address@hidden> wrote:
Hi Devin,

You wanted to ramp up/down the external PA: Use the GPIO pins, and the ATR registers [1] or timed commands issued over the message bus [2] to change their state

Best regards,
Marcus

[1] http://files.ettus.com/manual/page_gpio_api.html#xgpio_fpanel_atr
[2] http://gnuradio.org/doc/doxygen/page_uhd.html#uhd_command_syntax

On 08/18/2015 09:17 PM, devin kelly wrote:
Hello,
0

I'm transmitting a fairly bursty, irregularly timed signal. I attach a stream tag to the sample that has the start of the burst (tx_sob). I also have a PA that I can turn on and off that's inbetween my USRP B210 and antenna.

I'd like to be able to turn the PA on and off synchronously, say 50 ms before tx_sob is to be transmitted.

Is there any way to do this? I'm thinking I could add a new tag that's 50 ms before my transmission but then how would I synchronously turn on the PA? Is there something like a callback function I can use? Does the UHD or the UHD block have this functionality?

Thanks for any help,

Devin
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From:	devin kelly
Subject:	Re: [Discuss-gnuradio] Enveloping a transmit amplifier
Date:	Fri, 21 Aug 2015 08:59:20 -0400