This version (22 Jul 2019 11:24) was approved by Andrei Drimbarean.The Previously approved version (05 Jul 2013 14:24) is available.

AD74xx - No-OS Driver for Microchip Microcontroller Platforms

Supported Devices

Evaluation Boards

Reference Circuits

CN0178

Overview

The AD7476/AD7477/AD7478 are, respectively, 12-bit, 10-bit, and 8-bit, high speed, low power, successive approximation ADCs. The parts operate from a single 2.35 V to 5.25 V power supply and feature throughput rates up to 1 MSPS. Each part contains a low noise, wide bandwidth track-and-hold amplifier that can handle input frequencies in excess of 6 MHz.

The conversion process and data acquisition are controlled using CS the serial clock, allowing the devices to interface with microprocessors or DSPs. The input signal is sampled on the falling edge of CS and the conversion is initiated at this point. There are no pipeline delays associated with these parts.

The AD7476/AD7477/AD7478 use advanced design techniques to achieve very low power dissipation at high throughput rates. The reference for the parts is taken internally from VDD. This allows the widest dynamic input range to the ADC. Thus, the analog input range for the parts are 0 V to VDD. The conversion rate is determined by the SCLK.

01 Oct 2012 13:41 · 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 AD74xx 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 AD74xx driver can be used exactly as it is provided.

There are three functions which are called by the AD74xx driver:

SPI_Init() – initializes the communication peripheral.
SPI_Write() – writes data to the device.
SPI_Read() – reads data from the device.

SPI driver architecture

The following functions are implemented in this version of AD74xx driver:

Function	Description
char AD74xx_Init(char partNumber)	Initializes the device.
void AD74xx_PowerDown(void)	Powers down the device.
void AD74xx_PowerUp(void)	Powers up the device by performing a dummy read.
unsigned short AD74xx_GetRegisterValue(void)	Reads the conversion value.
float AD74xx_ConvertToVolts(unsigned short rawValue, float vRef)	Converts a raw sample to volts.

01 Oct 2012 14:39 · Dragos Bogdan

HW Platform(s):

Downloads

AD7476 DSPIC33 Driver
AD7476 chipKIT Driver
AD74xx Driver: https://github.com/analogdevicesinc/no-OS/tree/master/drivers/adc/ad74xx
PmodAD1 Demo for PIC32MX320F128H: https://github.com/analogdevicesinc/no-OS/tree/master/Microchip/PIC32MX320F128H/PmodAD1
PIC32MX320F128H Common Drivers: https://github.com/analogdevicesinc/no-OS/tree/master/Microchip/PIC32MX320F128H/Common

Digilent Cerebot MX3cK Quick Start Guide

This section contains a description of the steps required to run the AD7476 demonstration project on a Digilent Cerebot MX3cK platform.

Required Hardware

Required Software

MPLAB X Integrated Development Environment
MPLAB XC32 compiler
The AD7476 demonstration project for PIC32MX320F128H.

The AD7476 demonstration project for PIC32MX320F128H consists of three parts: the AD74xx Driver, the PmodAD1 Demo for PIC32MX320F128H and the PIC32MX320F128H Common Drivers.

All three parts have to be downloaded.

Hardware Setup

A PmodAD1 has to be connected to the JE connector of Cerebot MX3cK development board in this particulary way:

PmodAD1 J1 connector Pin CS  → Cerebot MX3cK JE connector Pin 1
PmodAD1 J1 connector Pin D0  → Cerebot MX3cK JE connector Pin 3
PmodAD1 J1 connector Pin CLK → Cerebot MX3cK JE connector Pin 4
PmodAD1 J1 connector Pin GND → Cerebot MX3cK JE connector Pin 5
PmodAD1 J1 connector Pin VCC → Cerebot MX3cK JE connector Pin 6

The reference voltage for the AD7476 is 3.3V.

Reference Project Overview

The following commands were implemented in this version of AD7476 reference project for Cerebot MX3cK board.

Command	Description
help?	Displays all available commands.
voltage?	Initiates a conversion and displays the voltage captured on A0 channel.
register?	Initiates a conversion and displays the value from the register.

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