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This version (02 Jul 2013 15:34) was approved by DragosB.The Previously approved version (09 Oct 2012 16:28) is available.Diff

AD7156 - No-OS Driver for Microchip Microcontroller Platforms

Supported Devices

Evaluation Boards

Overview

The AD7156 delivers a complete signal processing solution for capacitive sensors, featuring an ultralow power converter with fast response time.

The AD7156 uses an Analog Devices, Inc., capacitance-to-digital converter (CDC) technology, which combines features important for interfacing to real sensors, such as high input sensitivity and high tolerance of both input parasitic ground capacitance and leakage current.

The integrated adaptive threshold algorithm compensates for any variations in the sensor capacitance due to environmental factors like humidity and temperature or due to changes in the dielectric material over time.

By default, the AD7156 operates in standalone mode using the fixed power-up settings and indicates detection on two digital outputs. Alternatively, the AD7156 can be interfaced to a micro-controller via the serial interface, the internal registers can be programmed with user-defined settings, and the data and status can be read from the part.

The AD7156 operates with a 1.8 V to 3.6 V power supply. It is specified over the temperature range of −40°C to +85°C.

Applications

  • Buttons and switches
  • Proximity sensing
  • Contactless switching
  • Position detection
  • Level detection
  • Portable products

01 Oct 2012 11:36 · Dragos Bogdan

The goal of this project (Microcontroller No-OS) is to be able to provide reference projects for lower end processors, which can't run Linux, or aren't running a specific operating system, to help those customers using microcontrollers with ADI parts. Here you can find a generic driver which can be used as a base for any microcontroller platform and also specific drivers for different microcontroller platforms.

Driver Description

The driver contains two parts:

  • The driver for the AD7156 part, which may be used, without modifications, with any microcontroller.
  • The Communication Driver, where the specific communication functions for the desired type of processor and communication protocol have to be implemented. This driver implements the communication with the device and hides the actual details of the communication protocol to the ADI driver. The Communication Driver has a standard interface, so the AD7156 driver can be used exactly as it is provided.

There are three functions which are called by the AD7156 driver:

  • I2C_Init() – initializes the communication peripheral.
  • I2C_Write() – writes data to the device.
  • I2C_Read() – reads data from the device.

I2C driver architecture

The following functions are implemented in this version of AD7156 driver:

Function Description
void AD7156_GetRegisterValue(unsigned char* pReadData, unsigned char registerAddress, unsigned char bytesNumber) Performs a burst read of a specified number of registers.
void AD7156_SetRegisterValue(unsigned short registerValue, unsigned char registerAddress, unsigned char bytesNumber) Writes data into one or two registers.
char AD7156_Init(void) Initializes the communication peripheral and checks if the device is present.
void AD7156_Reset(void) Resets the device.
void AD7156_SetPowerMode(unsigned char pwrMode) Sets the converter mode of operation.
void AD7156_ChannelState(unsigned char channel, unsigned char enableConv) Enables or disables conversion on the selected channel.
void AD7156_SetRange(unsigned channel, unsigned char range) Sets the input range of the specified channel.
float AD7156_GetRange(unsigned channel) Reads the range bits from the device and returns the range in pF.
void AD7156_SetThresholdMode(unsigned char thrMode, unsigned char thrFixed) Selects the threshold mode of operation.
void AD7156_SetThreshold(unsigned char channel, float pFthr) Writes to the threshold register when threshold fixed mode is enabled.
void AD7156_SetSensitivity(unsigned char channel, float pFsensitivity) Writes a value(pF) to the sensitivity register. This functions should be used when adaptive threshold mode is selected.
unsigned short AD7156_ReadChannelData(unsigned char channel) Reads a 12-bit sample from the selected channel.
unsigned short AD7156_WaitReadChannelData(unsigned char channel) Waits for a finished CDC conversion and reads a 12-bit sample from the selected channel.
float AD7156_ReadChannelCapacitance(unsigned char channel) Reads a sample the selected channel and converts the data to picofarads(pF).
float AD7156_WaitReadChannelCapacitance(unsigned char channel) Waits for a finished CDC conversion the selected channel, reads a sample and converts the data to picofarads(pF).
01 Oct 2012 15:19 · Dragos Bogdan

Downloads

Digilent Cerebot MX3cK Quick Start Guide

This section contains a description of the steps required to run the AD7156 demonstration project on a Digilent Cerebot MX3cK platform.

Required Hardware

Required Software

The AD7156 demonstration project for PIC32MX320F128H consists of three parts: the AD7156 Driver, the PmodCDC1 Demo for PIC32MX320F128H and the PIC32MX320F128H Common Drivers.

All three parts have to be downloaded.

Hardware Setup

A PmodCDC1 has to be connected to the J2 connector of Cerebot MX3cK development board.

Reference Project Overview

The following commands were implemented in this version of AD7156 reference project for Cerebot MX3cK board.

Command Description
help? Displays all available commands.
channelRange? Displays the set range for the selected channel. Accepted values:
1 - Displays the channel 1's range.
2 - Displays the channel 2's range.
channelRange= Selects the range of the selected channel. Accepted values:
channel:
1 - Select channel 1.
2 - Select channel 2.
range:
0 - 0..2pF.
1 - 0..0.5pF
2 - 0..1pF
3 - 0..4pF.
powerMode? Displays the current power mode.
powerMode= Selects the power mode of the device. Accepted values:
0 - Idle.
1 - Continuous conversions.
2 - Single conversion.
3 - Power-down.
channelEnable= Enables or disabled conversions on selected channel. Accepted values:
channel:
1 - Select channel 1.
2 - Select channel 2.
enable:
0 - Disable conversions on selected channel.
1 - Enable conversions on selected channel.
samples? Reads 50 samples form the enabled channels and displays the data in pF.
buttons? Checks if any of the two buttons are pressed or released.
reset! Resets the device.

Commands can be executed using a serial terminal connected to the UART1 peripheral of PIC32MX320F128H.

The following image shows a generic list of commands in a serial terminal connected to processor’s UART peripheral.

Software Project Setup

This section presents the steps for developing a software application that will run on the Digilent Cerebot MX3cK development board for controlling and monitoring the operation of the ADI part.

  • Run the MPLAB X integrated development environment.
  • Choose to create a new project.
  • In the Choose Project window select Microchip Embedded category, Standalone Project and press Next.

  • In the Select Device window choose PIC32MX320F128H device and press Next.

  • In the Select Tool window select the desired hardware tool and press Next.

  • In the Select Compiler window chose the XC32 compiler and press Next.

  • In the Select Project Name and Folder window choose a name and a location for the project.

  • After the project is created, all the downloaded source files have to be copied in the project folder and included in the project.

  • The project is ready to be built and downloaded on the development board.

05 Jul 2012 14:45

Digilent Cerebot MC7 Quick Start Guide

This section contains a description of the steps required to run the AD7156 demonstration project on a Digilent Cerebot MC7 platform.

Required Hardware

Required Software

Hardware Setup

A PmodCDC1 can be connected to the J6 connector of Cerebot MC7 development board for I2C operation,

Reference Project Overview

Following commands were implemented in this version of AD7156 reference project for Cerebot MC7 board.

Command Description
help? Displays all available commands.
range= Selects the range of the channels. Accepted values: 0-3.
power= Selects the power mode of the device. Accepted values: 0 - 3.
channel1= Enables or disabled conversions on channel 1. Accepted values 0-1.
channel2= Enables or disabled conversions on channel 2. Accepted values 0-1.
samples? Reads 50 samples form the enabled channels and displays the data as pF.
buttons? Checks if any of the two buttons are pressed or released.
reset= Resets the device. Accepted value: 1.

Commands can be executed using a serial terminal connected to the UART1 peripheral of dsPIC33FJ128MC706A.

The following image shows a list of commands in a serial terminal connected to processor’s UART peripheral.

Software Project Setup

This section presents the steps for developing a software application that will run on the Digilent Cerebot MC7 development board for controlling and monitoring the operation of the ADI part.

  • Run the MPLAB X integrated development environment.
  • Choose to create a new project.
  • In the Choose Project window select Microchip Embedded category, Standalone Project and press Next.

  • In the Select Device window choose dsPIC33FJ128MC706A device and press Next.

  • In the Select Tool window select the desired hardware tool and press Next.

  • In the Select Compiler window chose the XC16 compiler and press Next.

  • In the Select Project Name and Folder window choose a name and a location for the project.

  • After the project is created, the source files have to be copied in the project folder and included in the project.

  • The project is ready to be built and downloaded on the development board.

16 Jul 2012 16:48

More information

01 Jun 2012 12:17