SoapySDR is a [C/C++ API](https://github.com/pothosware/SoapySDR/blob/master/include/SoapySDR/Device.hpp) that interfaces SDR hardware on one side and application software on the other. Due to its very generic nature it was fairly difficult to implement and specific UI widgets were developed to handle specific types of parameters. The level of control depends on how the device API was implemented by the vendors. On application side some parts of the API have not been implemented and can be left as possible enhancements (see next). In any case it is recommended to use the native plugins if they are available.
SoapySDR devices appear in the list of available devices in the order they are listed in the API call to SoapySDR. If more than one device controlled by SoapySDR is listed then its sequence number is incremented like:
The binary distributions provide only the SoapySDR base library. It is your responsibility to install SoapySDR in your system with the SoapySDR plugins suitable for your hardware.
Occasionally some devices may require to have the user specifying keyword parameters in order to open the device correctly. Most noticeably the Red Pitaya (driver `redpitaya`) needs the IP address of the board specified as a `addr=x.x.x.x` key value pair as it does not get scanned automatically.
In such a case you will use the device user arguments (Preferences -> Devices -> User arguments) with the dialog as described [here](../../../sdrgui/deviceuserargs.md)
It is very important NOT to use SoapySDR. The default parameters are set to flash the FPGA but as this does not succeeds it results in a FPGA image wipe out and the device returns in "Cypress" mode. It is not too difficult to recover but there is no point risking the hassle.
When installed the Red Pitaya SoapySDR plugin lists a Red Pitaya device even if there is no Red Pitaya attached. Trying to select and start it when there is no Red Pitaya will result in program crash.
The top part described by number tags is common for all devices. The bottom part under the "A" tag depends on the SoapySDR device implementation. The corresponding widgets are stacked vertically inside a scrollable area as there may be many controls depending on how the device interface is implemented in SoapySDR. Move the slider on the right to see all parameters available.
This is the center frequency of reception in kHz. The center frequency is usually the same for all Rx channels. The GUI of the sibling channel if present is adjusted automatically if necessary. This control corresponds to the first SoapySDR tuning element usually labeled as "RF" and would generally control the main local oscillator (LO).
Use the wheels to adjust the value. Left click on a digit sets the cursor position at this digit. Right click on a digit sets all digits on the right to zero. This effectively floors value at the digit position. Wheels are moved with the mousewheel while pointing at the wheel or by selecting the wheel with the left mouse click and using the keyboard arrows. Pressing shift simultaneously moves digit by 5 and pressing control moves it by 2.
- Blue triangle icon: device is ready and can be started
- Green square icon: device is running and can be stopped
- Magenta (or pink) square icon: an error occurred. In the case the device was accidentally disconnected you may click on the icon, plug back in and start again. Check the console log for possible errors.
- if decimation n is 4 or lower: Fc = SR/2^(log2(n)-1). The device center frequency is on the side of the baseband. You need a RF filter bandwidth at least twice the baseband.
- if decimation n is 8 or higher: Fc = SR/n. The device center frequency is half the baseband away from the side of the baseband. You need a RF filter bandwidth at least 3 times the baseband.
<h3>4: Decimation factor</h3>
The I/Q stream from the SoapySDR I/Q stream is downsampled by a power of two before being sent to the passband. Possible values are increasing powers of two: 1 (no decimation), 2, 4, 8, 16, 32, 64.
This button opens a dialog to set the transverter mode frequency translation options. The details about this dialog can be found [here](../../../sdrgui/gui/transverterdialog.md)
Use this slider to adjust SDRangel internal LO correction in ppm. It can be varied from -100.0 to 100.0 in 0.1 steps and is applied in software when calculating the frequency at which the LO should be set.
<h2>A: SoapySDR variable interface</h2>
The form of widgets is closely related to the type of setting defined in the [SoapySDR interface](https://github.com/pothosware/SoapySDR/blob/master/include/SoapySDR/Types.hpp). These are:
- Ranges
- Continuous range when maximum and minimum are different
- Discrete value when maximum and minimum are equal. Usually this appears in a range list to define a set of values
- List of ranges: more than one range applies to the same setting
Note that the same widget is used for single ranges and ranges list. In this case the range selection combo on the right is disabled. The manipulation of the dial is described in (1.1: Frequency)
If the range is in both the positive and negative domains the signed variation is used:
