AD7746-EBZ no-OS Example Project

See projects/ad7746-ebz (doxygen) for the Doxygen documentation.

The AD7746 is a high resolution, sigma-delta capacitance-to-digital converter (CDC). The capacitance input range is +/-4 pF (measured with respect to on-chip digital-to-capacitance DACs), with a common-mode capacitance up to 17 pF. The AD7746 also provides an on-chip temperature sensor with +/-2 degrees C accuracy and 0.1 degrees C resolution. Communication with the device is handled via a 2-wire I2C-compatible serial interface.

The EVAL-AD7746EBZ evaluation board provides a platform for evaluating the AD7746 capacitance-to-digital converter. It features SMB connectors for all capacitive input and excitation signals, and supports both single-ended and differential capacitance measurements.

Applications

Pressure measurement
Position sensing
Level sensing
Flowmeters
Humidity sensing
Impurity detection

Hardware Specifications

Power Supply Requirements

The EVAL-AD7746EBZ evaluation board operates on a 5V power supply through USB connector (J1), utilizing an on-board 3.3V regulator (ADP3303) to deliver the regulated voltage needed for the AD7746. The board also supports alternative power supply options of either 3V or 5V via an external input (J2). The AVDD voltage is selected through jumper LK1.

Board Connector and Jumper Settings

On-board Connectors

Please see the following table for the connector descriptions:

Connector

Description

USB (J1)

Provides 5 V power supply and data communication interface

External Power (J2)

Alternative power supply option of 3 V or 5 V

CIN1+, CIN1- (SMB)

Capacitive input connectors for measurement

EXCA, EXCB (SMB)

Excitation output connectors for capacitive sensing

LK1

Jumper to select AVDD voltage (3.3 V or 5 V)

LK2

I2C header (SDA, SCL, RDY) for external controller access

No-OS Build Setup

Please see: https://wiki.analog.com/resources/no-os/build

No-OS Supported Examples

The initialization data used in the examples is taken out from: Project Common Data Path

Capacitive Length Demo

This is the default example that:

Initializes the AD7746 capacitance-to-digital converter
Calibrates the capacitive input using a two-point calibration (0 mm and 51 mm)
Continuously reads and displays the ruler position in mm and internal temperature in degrees C
Outputs measurements every 2 seconds over UART

IIO Example

This example initializes an IIOD server on the AD7746 evaluation board, enabling it to connect with IIO clients. The IIO application initiates the AD7746 sensor for capacitive and temperature measurements, including enabling capacitance channels and setting temperature read modes. Users can connect using an IIO client such as the IIO Oscilloscope to manage device settings, including offset, sampling frequency, and raw data conversion. Communication is handled via a UART interface.

If you are not familiar with ADI IIO Application, please take a look at: IIO No-OS

If you are not familiar with ADI IIO Oscilloscope Client, please take a look at: IIO Oscilloscope

To build the IIO example, add the following flag when invoking make:

# to build the IIO example
make IIOD=y

No-OS Supported Platforms

ADuCM3029 Platform

Used Hardware

Connections

Before connecting the EVAL-AD7746EBZ to the EVAL-ADICUP3029, remove the links on LK2 to disconnect the on-board USB microcontroller from the I2C bus.

EVAL-AD7746EBZ Pin	EVAL-ADICUP3029 Pin	Function
VDD (3.3V)	3.3V	Power supply
GND	GND	Ground
SDA (LK2)	P0.14	I2C data line
SCL (LK2)	P0.15	I2C clock line

Build Command

# to delete current build
make reset PLATFORM=aducm3029
# to build the project
make PLATFORM=aducm3029
# to flash the code
make run PLATFORM=aducm3029