ad9361: Add RX overload sensor

host/docs/devices/usrp_b200.dox

@@ -261,6 +261,21 @@ The TX path and the two RX paths have their own calibration data, resulting in
 Devices have to be manually calibrated using a calibrated power meter or
 signal generator.
 
+\subsection b200_fe_sensors Frontend sensors
+
+Each receive frontend provides these sensors, read with
+uhd::usrp::multi_usrp::get_rx_sensor():
+
+- `lo_locked`: True if the RX LO is locked.
+- `rssi`: RSSI value as returned from the AD9361, in dB.
+- `temp`: Temperature of the AD9361, in degrees Celsius.
+- `overload`: Integer with the RX overload signals of the AD9361 for this
+  chain (registers 0x2B8 and 0x2B9): bit 4 large LMT overload, bit 3 small
+  LMT overload, bit 2 large ADC overload, bit 1 small ADC overload, bit 0
+  digital saturation. The LMT bits detect an overload of the RF front end,
+  which can be caused by a strong signal outside the captured band and does
+  not show as clipped samples. The bits stay set until the next gain change.
+
 \section b200_hw_ref Hardware Reference
 
 \subsection b200_hw_ref_leds LED Indicators

host/lib/include/uhdlib/usrp/common/ad9361_ctrl.hpp

@@ -142,6 +142,12 @@ class ad9361_ctrl : public uhd::noncopyable
     //! read internal RSSI sensor
     virtual sensor_value_t get_rssi(const std::string& which) = 0;
 
+    //! read the RX overload signals (LMT, ADC, digital saturation)
+    virtual sensor_value_t get_overload(const std::string& which)
+    {
+        throw uhd::not_implemented_error("get_overload: " + which);
+    }
+
     //! read the internal temp sensor
     virtual sensor_value_t get_temperature() = 0;
 

host/lib/usrp/common/ad9361_ctrl.cpp

@@ -204,6 +204,16 @@ class ad9361_ctrl_impl : public ad9361_ctrl
         return sensor_value_t("RSSI", _device.get_rssi(chain), "dB");
     }
 
+    //! read the RX overload signals of the chain
+    sensor_value_t get_overload(const std::string& which) override
+    {
+        std::lock_guard<std::mutex> lock(_mutex);
+
+        ad9361_device_t::chain_t chain = _get_chain_from_antenna(which);
+        return sensor_value_t(
+            "overload", static_cast<int>(_device.get_overload(chain)), "");
+    }
+
     //! read the internal temp sensor. Average over 3 results
     sensor_value_t get_temperature() override
     {

host/lib/usrp/common/ad9361_driver/ad9361_device.cpp

@@ -2301,6 +2301,12 @@ double ad9361_device_t::get_rssi(chain_t chain)
     return rssi;
 }
 
+uint8_t ad9361_device_t::get_overload(chain_t chain)
+{
+    const uint32_t reg = (chain == CHAIN_1) ? 0x2B8 : 0x2B9;
+    return _io_iface->peek8(reg) & 0x1F;
+}
+
 /*
  * Returns the reading of the internal temperature sensor.
  * One point calibration of the sensor was done according to datasheet

host/lib/usrp/common/ad9361_driver/ad9361_device.h

@@ -192,6 +192,11 @@ class ad9361_device_t : public uhd::noncopyable
     /* Read back the internal RSSI measurement data. */
     double get_rssi(chain_t chain);
 
+    /* Read the RX overload signals of a chain (register 0x2B8/0x2B9):
+     * bit 4 large LMT, 3 small LMT, 2 large ADC, 1 small ADC, 0 digital
+     * saturation. */
+    uint8_t get_overload(chain_t chain);
+
     /*! Read the internal temperature sensor
      *\param calibrate return raw sensor readings or apply calibration factor.
      *\param num_samples number of measurements to average over

host/lib/usrp/common/ad936x_manager.cpp

@@ -225,6 +225,10 @@ class ad936x_manager_impl : public ad936x_manager
             subtree->create<sensor_value_t>("sensors/rssi").set_publisher([this, key]() {
                 return this->_codec_ctrl->get_rssi(key);
             });
+            subtree->create<sensor_value_t>("sensors/overload")
+                .set_publisher([this, key]() {
+                    return this->_codec_ctrl->get_overload(key);
+                });
         }
 
         // Gains