[USRP-users] Problems with the C++ API

Dubach Marco dubam1 at bfh.ch
Mon Jun 18 03:16:23 EDT 2012

Dear Sir and Madam

I want to send samples form one USRP to another one.

I work with USRP N210.
I'm using a LFTX-LF REV 2.2 and a LFRX-LF REV 2.2 daughterboard.
I'm using Firmware/FPGA  uhd-images_003.004.000-42-gc402ed8c.
The installed Driver is 003.004.002.
I'm using the API for C++.

To send/receive samples, I'm using your Examples "tx_samples_from_file" and "rx_samples_to_file".

Finally, I want transmit 8bit samples with 50MS with the USRP.

I read, that it is necessary to use the "sc8" mode to send/receive 8bit samples.

In the example "rx_samples_to_file" it is easy to activate the sc8 mode over the console by -wirefmt sc8.

My problem is now to modify the example "tx_samples_from_file" to send samples into the 8bit mode over the wire.
I read, in the doxygen-documentation of the class "uhd::stream_args_t Struct Reference",  that I need to set the peak value to "max_sample_level/full_scale_level"  for using sc8 samples over the wire.

How can I modify this peak value? Because in the source Files I didn't find any Attribute like peak to modify.
Do I need to modify also the "rx_samples_to_file"-example?

What have I to modify in addition to send/receive some sc8 samples over the wire?

I hope you can help me.

Kind regards

Marco Dubach
Bern University of Applied Sciences

Abstract of the doxygen:
     * - peak: specifies a fractional sample level to calculate scaling with the sc8 wire format.
     * When using sc8 samples over the wire, the device must scale samples
     * (both on the host and in the device) to satisfy the dynamic range needs.
     * The peak value specifies a fraction of the maximum sample level (1.0 = 100%).
     * Set peak to max_sample_level/full_scale_level to ensure optimum dynamic range.

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