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I have been working on a C++ device driver that utilizes the libbladeRF library to control the bladeRF.

When trying to implement the synchronous transfer interafce, I am seeing an unexpected transmission from the bladerf whenever I execute the bladerf_enable_module command for the TX module. My sequence of events is as follows:

- run bladerf_sync_config
- run bladerf_enable_module
- check if there is data to be transferred and, if so,
- run bladerf_sync_tx to transfer said data.

I tested the code without any test data to ensure it was configuring properly, and I saw a peak on my spectrum analyzer at the set frequency. I hooked the bladeRF up to an oscilloscope and it showed that the signal was a sine wave at the carrier frequency. Is it an expected behavior for the bladeRF to transmit an unmodulated carrier signal if the TX module has been enabled but the bladerf_sync_tx command is not called to specify a data buffer to transmit? Or is there something I am missing here?

thanks!
-jimmy37

Yes, this is expected. You'll likely seeing a bit of DC offset on the TX channel, and there are means to calibrate it out. Check out this wiki page, and I think this will become a little bit more clear.

Cheers,
Jon