AD719x IIO Application

Introduction

This page gives an overview of using the ARM platforms supported (default is Mbed) firmware example with Analog Devices AD719x Evaluation board and SDP-K1 controller board. This example code leverages the ADI developed IIO (Industrial Input Output) ecosystem to evaluate the AD719x device by providing device debug and data capture support.

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IIO Oscilloscope is used as a client application running on Windows, which is an ADI-developed GUI for ADC data visualization and device debug. The interface used for communicating the client application with the firmware application (IIO device) is UART. The firmware application communicates with the IIO device using ADI No-OS drivers and platform drivers low level software layers. SDP-K1 is used as the controller board, on which the IIO firmware application runs.

Note

SDP-K1 can also support high speed VirtualCOM port at 1 Mbps or higher for faster data transmission.

This code has been developed and tested on the SDP-K1 Controller Board using the on-board SDP-120 Headers. However, the same code can be used without or with little modification on any Mbed enabled board which has Arduino Header support, such as STM32-Discovery, STM32-Nucleo, etc.

Hardware Connections

Jumper Settings

SDP-K1: Connect the VIO_ADJUST jumper on the SDP-K1 board to the 3.3 V position to drive SDP-K1 GPIOs at 3.3 V.

EVAL-AD719X:

  • Stack the EVAL-AD719X-ASDZ on the Arduino connectors of the SDP-K1 board.

  • Connect a male-to-male jumper wire between D8 and D12 on the Arduino connectors.

  • Set the LK7 and LK8 jumper headers to 3.3 V.

  • Set LK12 jumper header to position A.

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UART Connections

For data transmission to the IIO client, VirtualCOM or UART serial communication is used. SDP-K1 by default uses the VCOM serial interface for higher speed data transmission.

SDP-K1 is powered through USB connections from the computer. SDP-K1 acts as a serial device when connected to a PC, which creates a COM port to connect to IIO Oscilloscope GUI running on Windows. The COM port assigned to a device can be seen through the Device Manager.

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SDP-K1 can support high speed VirtualCOM port USB interface, so by default VCOM is configured as the default interface in the firmware. The interface can be set to UART by defining the macro USE_PHY_COM_PORT in the app_config.h file.

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Note

The actual COM port number for your device may not be the same as shown above. Always check your SDP-K1 serial COM port number before connecting to the IIO client.

Software Downloads

MBED Firmware

Source code is hosted in the precision-converters-firmware repository.

Build guide: Precision Converters MBED Firmware

Libiio: IIO Library

This library provides an abstracted interface to communicate between the IIO device and the IIO client application (IIO Oscilloscope) without worrying about the low level hardware details.

IIO Oscilloscope (Client)

This is a GUI-based IIO client application for data visualization and device configuration/debugging. The data from IIO devices (ADCs/DACs) is transmitted over Serial/Ethernet/USB link to IIO Oscilloscope through the abstracted layer of libiio.

Evaluating AD719x Using IIO Ecosystem

Ensure that the hardware connection has been made properly between the Controller Board (SDP-K1) and the ADC Eval board. Also ensure all software (IIO firmware, libiio, and IIO Oscilloscope) is downloaded and installed on your computer before trying to communicate with the device.

Running IIO Oscilloscope (Client)

Open the IIO Oscilloscope application from the start menu and configure the serial (UART) settings as shown below. Click the refresh button and the AD719x device should appear in the IIO devices list.

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Click “Connect” and it should by default open the data “Capture” window. You can drag aside or close this window to see the main “Debug and DMM” tab window.

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Configure/Access Device Attributes (Parameters)

The IIO Oscilloscope allows the user to access and configure different device parameters, called “Device Attributes”. There are 2 types of attributes:

  • Device Attributes (Global): Access/Configure common device parameters.

  • Channel Attributes (Specific to channels): Access/Configure channel specific device parameters.

How to read and write an attribute:

  • To read an attribute, simply select the attribute from the list or press the “Read” button on the left side.

  • To write an attribute, select the attribute value in the “value field” and press the “Write” button.

Using DMM Tab to Read DC Voltage on Input Channels

The DMM tab can be used to read the instantaneous voltage applied on analog input channels. Simply select the device and channels to read and press the start button.

Note

The voltage is just instantaneous, so it is not possible to get RMS AC voltage or averaged DC voltage. Also, when using the DMM tab, do not access/use the Data Capture or Debug tab as this could impact data capturing. Both DMM scan and data capture use different methods of conversion. The DMM data is read using single conversion, while data capture uses continuous conversion mode of operation.

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Data Capture from IIO Device

To capture data from the AD719x IIO device, simply select the device and channels to read/capture data. The data is plotted as “ADC Raw Value” vs “Number of Samples” and is used for visualization. The data is read as-is from the device without any processing. If the user wants to process the data, it must be done externally by capturing data from the serial link on the controller board.

Note

The DMM or Debug tab should not be accessed when capturing data as this would impact data capturing. Both DMM scan and data capture use different methods of conversion. The DMM data is read using single conversion, while data capture uses continuous conversion mode of operation.

Time Domain Plot

Note

When enabling more than 4 channels, the number of samples should be decreased to 200 to avoid timeout in the IIO Oscilloscope.

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Frequency Domain Plot

Note

Max 4096 samples can be selected for plotting frequency domain response due to limited buffer size in the firmware.

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Python Environment and Scripts

Data capture, device calibration, etc. can be achieved with Python-based IIO clients, using the pyadi-iio library. A possible option using ADI’s pyadi-iio library in Python has been demonstrated in the following sections. The Python scripts are provided along with the firmware package.

Setting-up Python Environment

  • Install Python on your local machine. The scripts are developed and tested using Python 3.8.0; version 3.8.0 or newer is recommended.

  • Once Python is installed, make sure the environment path (on Windows) is set properly. Verify by running python --version on a command line tool such as Git Bash, Command Prompt, or PowerShell.

  • Install the pyadi-iio package by running python -m pip install pyadi-iio.

  • Install additional support packages by running python -m pip install -r requirements.txt from the scripts/ directory.

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Modifying/Running Python Scripts

  • All Python scripts specific to the AD719x IIO firmware are stored in the scripts folder in the project directory.

  • Ensure that the firmware is compiled with the noise testing mode, using the macros in the app_config.h file.

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  • Update the uri interface in the script according to the COM port assigned to your device (SDP-K1). Default COM port is set to COM16 in all scripts.

  • Update the device_name variable to match the device name in the compiled firmware.

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  • Enable the channel and set the size of the sample block for noise analysis.

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Output Obtained from the Python Script

While executing ad719x_rms_50hz_test.py, the command prompt requests the number of samples to be entered by the user. This should be a multiple of the defined sample block size. On successful completion of capturing n samples, the noise data is displayed on the screen and the data points are stored in a CSV file as adc_data_capture.csv in the folder where the script is located.

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AD719x Firmware Structure

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app_config.h

This file can be used to:

  • Select the active platform using the macro ACTIVE_PLATFORM_MBED (only Mbed is supported).

  • Select UART baud rate (for physical UART port) using the IIO_UART_BAUD_RATE macro. Default is 230400.

  • Select burst capture mode or continuous capture mode using the DATA_CAPTURE_MODE macro.

  • Select the active device by defining DEV_AD7193. Default is AD7193.

  • Uncomment the BIPOLAR_MODE macro to enable bipolar mode. Default is unipolar mode.

  • Uncomment the DIFFERENTIAL_INPUT macro to enable differential input. Default is pseudo differential input.

ad719x_user_config.c/.h

These files define the user configurations for the AD719x, such as SPI parameters (frequency, mode, etc.) and other init parameters used by No-OS drivers to initialize the AD719x device (gain, data output rate, reference voltage, etc.).

ad719x_data_capture.c

This file implements the data capturing logic for the AD719x device. The data capturing can be done using normal burst mode or continuous mode.

ad719x_iio.c

This file defines getter/setter functions for all the device and channel specific attributes (related to AD719x devices) to read/write the device parameters. The majority of device specific functionality is present in this module.

No-OS Drivers for AD719x

The No-OS drivers provide the high level abstracted layer for the digital interface of AD719x devices. The complete digital interface (to access the memory map and perform data read) is done in integration with platform drivers. The functionality related to No-OS drivers is covered in the following files:

  • ad719x.c

  • ad719x.h