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Industrial I/O (IIO) - ADALM-Pluto SDR Integration#

Authors: Andrei-Fabian Pop (Analog Devices Inc.)
Supported platforms: x86_64, aarch64
Language: C++
Last modified: August 26, 2025
Latest version: 1.0.0
Minimum Holoscan SDK version: 0.6.0
Tested Holoscan SDK versions: 0.6.0
Contribution metric: Level 3 - Developmental

Overview#

This application demonstrates how to use the IIO (Industrial I/O) operators to interface with Software Defined Radio (SDR) devices, specifically the ADALM-Pluto SDR from Analog Devices. The application showcases real-time signal generation, transmission, and reception capabilities using the Holoscan SDK framework.

What is ADALM-Pluto?#

The ADALM-Pluto (Active Learning Module) is an affordable, portable SDR platform that can transmit and receive RF signals from 325 MHz to 3.8 GHz. It features: - AD9363 transceiver chip - USB-powered operation - 20 MHz bandwidth (upgradeable to 56 MHz) - Support for various modulation schemes - Multiple input/output channels for data streaming

Application Capabilities#

This application provides examples of: 1. Attribute Reading/Writing: Configure SDR parameters like sampling rate, gain, and frequency 2. Buffer Operations: Stream raw buffer data through device channels for signal transmission and reception 3. Device Configuration: Apply complex device settings from YAML configuration files 4. Signal Generation: Create and transmit test signals through buffer channels

Use Cases#

  • RF Signal Analysis: Capture and analyze radio frequency signals in real-time
  • Communications Research: Prototype and test wireless communication systems
  • Educational Labs: Learn about SDR concepts and digital signal processing
  • IoT Development: Test and debug wireless IoT protocols
  • Amateur Radio: Digital mode experimentation and signal monitoring
  • Data Acquisition: High-speed streaming of ADC/DAC samples

Architecture#

The application uses the IIO (Industrial I/O) Linux subsystem to communicate with the ADALM-Pluto device. The IIO framework provides a standardized interface for: - Reading/writing device attributes (frequency, gain, sample rate) - Streaming raw data buffers through device channels - Managing device states and configurations

Requirements#

Hardware#

  • ADALM-Pluto SDR device
  • USB connection to host computer
  • Optional: Antennas for RF transmission/reception

Software#

  • Holoscan SDK
  • libiio library (version 0.x)
  • Network connection to Pluto (default IP: 192.168.2.1), connecting through usb requires minimal code modifications

Quick Start#

1. Connect ADALM-Pluto#

Connect your ADALM-Pluto to your computer via USB. The device will appear as a network interface with IP address 192.168.2.1.

2. Build the Application#

# From HoloHub root directory
./dev_container build_and_run iio

3. Run Examples#

The application includes several example modes:

Transmit a Test Signal#

# Transmits a sine wave on the configured frequency
./run launch iio python

Read Device Attributes#

Uncomment the attr_read_example() line in the compose() method to read device parameters.

Configure Device from YAML#

Uncomment the configurator_example() line to apply settings from iio_config.yaml.

Run the Pluto FFT example#

The C++ FFT example (cpp/pluto_fft_example) demonstrates real-time FFT visualization of RF signals captured from the ADALM-Pluto:

# Build and run the FFT example
./run build iio cpp
./run launch iio cpp

This example captures IQ samples from the Pluto SDR and displays a real-time FFT spectrum:

Pluto FFT Real-time Visualization

Configuration#

Network Settings#

The default URI for ADALM-Pluto is ip:192.168.2.1. Modify the G_URI variable in the Python script if your device has a different IP address.

Signal Parameters#

In the BasicIIOBufferEmitterOp class: - frequency: Sine wave frequency (Hz) - amplitude: Signal amplitude - sample_rate: Samples per second - total_samples: Number of samples per buffer

Channel Configuration#

  • G_NUM_CHANNELS: Set to 1 or 2 for single/dual channel operation

Example Workflows#

1. Signal Generation and Transmission#

The buffer write example generates a sine wave and transmits it through the SDR: 

# Generates 8kHz sine wave with amplitude 408
data_vector = self.generate_sinewave(total_samples, frequency=8, amplitude=408, sample_rate=400)

2. Signal Reception#

The buffer read example captures IQ samples from the RF input: 

# Captures 8192 samples from the receiver
iio_buf_read_op = IIOBufferRead(
    samples_count=8192,
    enabled_channel_names=["voltage0", "voltage1"]
)

3. Device Configuration#

The YAML configuration allows complex device setup: 

devices:
  - ad9361-phy:
      attrs:
        - ensm_mode: "fdd"
        - calib_mode: "manual"

Understanding Channel Data#

The ADALM-Pluto provides multiple channels for data streaming: - voltage0, voltage1: Independent channels that can be used for different data streams - Channel Types: Each channel can be configured as input or output - Data Format: Raw 16-bit signed integer samples - Buffer Organization: Samples from enabled channels are interleaved in the buffer

For example, with two channels enabled: - Single channel: [S0, S1, S2, S3, ...] where S represents samples from that channel - Dual channel: [Ch0_S0, Ch1_S0, Ch0_S1, Ch1_S1, ...] where samples alternate between channels

Note: The actual interpretation of the data (whether it represents I/Q components, real signals, or other data types) depends on your application and how you process the raw samples. The IIO operators simply provide raw buffer access without any automatic data conversion.

Troubleshooting#

  1. Connection Issues: Ensure ADALM-Pluto is recognized as a network device (check with ping 192.168.2.1 or using iio_info -S from libiio)
  2. Buffer Overruns: Reduce sample count or increase processing speed
  3. Signal Quality: Check antenna connections and gain settings
  4. Permission Errors: May need to run with appropriate permissions for USB device access

References#