Fobos SDR and SDR++: Why You Should Use the RigExpert Plugin
Fobos SDR supports operation with SDR++, but the level of support depends on which module (plugin) is used. To get the full functionality of Fobos SDR, we recommend using the SDR++ Plugin from RigExpert, which was specifically developed for Fobos SDR and supports all device capabilities.
The plugin is available on GitHub: rigexpert/SDRPlusPlus.
Basic Fobos SDR support in the official SDR++ project is only partial and is based on the Standard API. As a result, some receiver capabilities are unavailable or work with limitations.
The RigExpert plugin, on the other hand, provides full integration with Fobos SDR and uses all available capabilities of the device API.
Key Advantages of the RigExpert Plugin
Compared with the standard Fobos SDR support in SDR++, the RigExpert plugin provides:
- full support for the Fobos SDR API;
- display of the API library version, firmware version, and device revision;
- on-the-fly sample rate changes without restarting SDR++;
- on-the-fly switching between RF/HF inputs;
- native operation with HF channels;
- support for HF1 + HF2 IQ mode;
- GPIO control;
- optimized USB and CPU usage;
- stable operation even when using multiple receivers simultaneously.
Improved Performance
One of the key advantages of the RigExpert plugin is its optimized data transfer architecture. The plugin uses asynchronous USB operation with buffering, which allows it to:
- reduce the load on the USB controller;
- reduce CPU load when working with narrow bandwidths;
- improve reception stability;
- minimize the risk of data loss during high-speed reception.
Additional Capabilities
The RigExpert plugin also supports features that are not available in the standard implementation:
- correct retrieval of device information;
- complete resource management after operation is finished;
- full validation of the results returned by all API calls;
- GPIO support;
- dynamic changes to receiver operating parameters without reconnecting the device.
Technical Comparison
| Compared Feature | Official SDR++ Project | SDR++ Plugin by RigExpert |
| Support enabled in source code | Disabled by default; the build recipe must be edited | Enabled by default; no editing is required |
| Stream reception implementation | Synchronous (not the primary mode for libusb and libfobos; may become unstable at high data rates) | Asynchronous (the primary mode for libusb and libfobos; preferred for high data rates) |
| Buffer size | SampleRate/400 — too small, resulting in very frequent USB transactions, increasing the load on the USB infrastructure and potentially causing data-stream integrity issues | Constant 131072, with minimal impact on the USB infrastructure |
| Number of USB buffers | 1, due to synchronous mode | 32 |
| In destructor ~FobosSDRSourceModule() | // Nothing to do — this is incorrect | Streams are stopped, the connection to the device is closed, and resources are released |
| Retrieval of API library and device information | Not available | Properly implemented |
| Validation of API function return values | Simplified; only the main functions are checked | Full; all return values are checked |
| GPIO line control | Not implemented | Implemented |
| On-the-fly sample rate change | Not implemented | Implemented |
| On-the-fly signal input switching | Not implemented | Implemented |
