I have a design where I am using only the receive portion of the AD9361. I'm leveraging the reference design, and I've made software that utilizes the IIO driver (iio_utils.c/h). Because of how great the IIO driver is, I haven't yet had to do any direct register writes via SPI or anything to configure the RFIC.
However, I'm trying to find out how to disable the transmit and I'm not sure how to do this with the IIO driver. The reason is that I've seen some leakage to the RX ports that is affected by the TX LO frequency (e.g. a tone at ~4.9GHz on the RX when TXing at 2.4GHz, and the locatation of this tone moves as the TX LO changes) and also want to save power. I'm not as concerned with removing the TX HDL in the FPGA and even the TX in the devicetree/kernel drivers/etc., and really just need a way to bitbang the 9361 to turn off TX.
Things I've tried which haven't solved the problem:
- Setting all "out_voltage*_en" to 0
- Maximizing TX attenuation eliminates the signal out the TX port, but doesn't do anything with the leakage.
- Setting "out_altvoltage0_TX1_I_F1_raw" to 0 (this is what the IIO Oscilloscope does to disable the DDS)
Thanks for helping!