Hi Thomas,
On Sun, Jun 10, 2012 at 4:58 AM, Thomas Tsou thomastsou@gmail.com wrote:
On Sat, Jun 9, 2012 at 9:30 AM, Alexander Chemeris alexander.chemeris@gmail.com wrote:
Hi Thomas,
If we get a UmTRX to you, could you make OpenBTS to run with it quickly, like before the end of the month? No matter how hackish the solution would be. We just need a way to start testing the hardware performance in a more real situation. Then we could target a cleaner solution.
To recap - right now we could transmit on a single channel, and receive on both channels, but the control of LMS chips is done by an external python script. I.e. to tune and set bandwidth, gain, etc you have to run this script before claiming a device with UHD.
FYI, I was finishing plans to attend the openhere festival in Dublin at the end of the month. That is in two weeks.
Oh, that's great! So hopefully see you there! Andrey Sviyazov is going to be there as well.
What is the state of OpenBTS integration right now?
OpenBTS starts with this change:
diff --git a/Transceiver52M/UHDDevice.cpp b/Transceiver52M/UHDDevice.cpp index d4ba580..4baf824 100644 --- a/Transceiver52M/UHDDevice.cpp +++ b/Transceiver52M/UHDDevice.cpp @@ -48,7 +48,8 @@
tx_ampl - Transmit amplitude must be between 0 and 1.0 */ -const double master_clk_rt = 52e6; +//const double master_clk_rt = 52e6; +const double master_clk_rt = 13e6; const size_t smpl_buf_sz = (1 << 20); const float tx_ampl = .3;
But the behavior is a bit strange - when I start OpenBTS transceiver starts to consume 100% of CPU and doesn't transmit. After a while (a minute or so) CPU usage drops and I start seeing a signal at the UmTRX output. I had no time to look into this deeply.
Can you transmit a beacon signal?
Yes. I could see the network with a phone. Signal hound pictures: 1) umtrx-openbts-spectrum.PNG - spectrum, generated by OpenBTS. 2) umtrx-openbts-timeslots.PNG - the same, but with zero span. 3) "GMSK VGA1 -5, VGA2 18, channel power 750kHz.PNG" and "Tx_GMSK#6(hot)_240412.png" are spectrum of a pure continuous GMSK signal, transmitted with UmTRX (captured by me and Andrey Sviyazov).
If UmTRX can support tuning, gain, and full duplex streaming with the existing UHD timestamp interface, then it shouldn't take long for OpenBTS.
Great!
Actually I should just try to run it - may be it will work right away? :)
I can use any reasonable sample rate for testing.
FYI: We use 13MHz
Is the external python script in a repository?
Yes. https://github.com/chemeris/UHD-Fairwaves/blob/fairwaves/umtrx-dboard/host/u...
Not everything is implemented, but it's easy to amend it.
