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AD5172 - Microcontroller No-OS Driver

Supported Devices

AD5172

Evaluation Boards

EVAL-AD5172SDZ

Overview

The AD5172 is a dual-channel, 256-position, one-time programmable (OTP) digital potentiometer that employs fuse link technology to achieve memory retention of resistance settings. OTP is a cost-effective alternative to EEMEM for users who do not need to program the digital potentiometer setting in memory more than once. The AD5172 is programmed using a 2-wire, I2C®-compatible digital interface. Unlimited adjustments are allowed before permanently setting the resistance value. During OTP activation, a permanent blow fuse command freezes the wiper position (analogous to placing epoxy on a mechanical trimmer). Unlike traditional OTP digital potentiometers, the AD5172 has a unique temporary OTP overwrite feature that allows for new adjustments even after a fuse is blown. However, the OTP setting is restored during subsequent power-up conditions. This allows users to treat this digital potentiometer as volatile potentiometer with a programmable preset.

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 Renesas platforms.

HW Platform(s):

Renesas Demo Kit for RL78G13 (Renesas)

Driver Description

The driver contains two parts:

The driver for the AD5172 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 AD5172 driver can be used exactly as it is provided.

There are three functions which are called by the AD5172 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 AD5172 driver:

Function	Description
unsigned char AD5172_Init(void)	Initializes the communication with the device.
void AD5172_Shutdown(unsigned char channel, unsigned char flag)	Sets or clears the Shutdown bit.
void AD5172_Otp(unsigned char channel, unsigned char data)	The channel is being one-time programmed(OTP).
void AD5172_WriteRDAC(unsigned char channel, unsigned char data)	Sends data to one of the 2 channels available.
unsigned char AD5172_ReadRDAC(unsigned char channel)	Reads a byte form the selected channel.

Downloads

Renesas RL78G13 Quick Start Guide

This section contains a description of the steps required to run the AD5172 demonstration project on a Renesas RL78G13 platform.

Required Hardware

Required Software

Hardware Setup

An EVAL-AD5172SDZ has to be interfaced with the Renesas Demonstration Kit (RDK) for RL78G13:

  EVAL-AD5172SDZ A connector Pin SCL_BF  (SCL)    → YRDKRL78G13 J9 connector Pin 1
  EVAL-AD5172SDZ A connector Pin SDA_BF  (SDA)    → YRDKRL78G13 J9 connector Pin 3

Software Setup

With the Applilet3 for RL78G13 tool the following peripherals have to be configured:

IICA0 (Inter Integrated Circuit Bus) - For the AD5172 part

Choose the Single master transfer mode and configure the interface with the following settings:

Clock mode setting: fCLK/2
Local address setting – Address: 16
Operation mode setting : Standard
Operation mode setting – Transfer clock (fSCL): 100000 (bps)
Interrupt setting – Communication end interrupt priority (INTIICA0): Low
Callback function setting: Check Master transmission end and Master reception end callback functions
Callback function enhanced feature setting: Check the Callback function enhanced feature setting.

CSI10 (Clocked Serial Interface 10) – For the ST7579 LCD

Choose to generate the Transmit/receive function for the CSI10 and configure the interface with the following settings:

Transfer mode setting: Single transfer mode
Data length setting : 8 bits
Transfer direction setting: MSB
Specification of data timing: Type 1
Transfer rate setting – Clock mode: Internal clock (master)
Transfer rate setting – Baudrate: 1000000 (bps)
Interrupt setting – Transfer interrupt priority (INTCSI10): Low
Uncheck the callback functions.

TM00 (Timer 00) – For the DelayMs() function

Configure TM00 as an interval timer:

Interval timer setting - Interval value(16 bits): 1 ms
Interval timer setting - Uncheck Generates INTM00 when counting is started
Interrupt setting - Uncheck End of timer channel 0 count, generate an interrupt (INTM00)

Watchdog Timer

Disable the watchdog timer:

Choose for the Watchdog timer operation setting: Unused option.

Reference Project Overview

The reference project initializes the device, writes two different values to both channels available on the device and then checks if the values were correctly written by reading the RDACs and displays them on the LCD.

Software Project Setup

This section presents the steps for developing a software application that will run on the Renesas Demo Kit for RL78G13 for controlling and monitoring the operation of the ADI part.

Two software applications have to be used: Applilet3 for RL78G13 (a tool that automatically generates device drivers for MCU peripheral functions) and IAR Embedded Workbench for Renesas RL78 (the integrated development environment).

Step 1 - Applilet3 for RL78G13

Run the Applilet3 for RL78G13 tool and create a new project for R5F100LE processor. Select IAR Compiler build tool, a project name, a location for the new project and press OK.

Keep the default Pin assignment setting and click Fix settings.

Now the desired peripherals can be configured and the code can be generated. For example, if the clocked serial interface 10 (CSI10) has to be configured, select the Serial peripheral, choose for the Channel 2 of Serial Array Unit 0 (SAU0) the CSI10 interface, Transmit/receive function option and then go to CSI10 tab.

To configure the CSI10 interface for serial transmissions of 8 bits, with MSB first, with the data captured on clock's rising edge, with a frequency of the clock of 1 MHz and the idle state high, the settings from the following image have to be made.

After all the desired peripherals are configured click on the Generate Code button and a new workspace and a new project for the IAR Embedded Workbench will be generated. After the code was generated close the Applilet3 for RL78G13 tool.

Step 2 - IAR Embedded Workbench for Renesas RL78

Run the IAR Embedded Workbench and open the workspace created with the Applilet3 tool.

Copy the files extracted from the zip file into the user_src folder, located in the project’s folder.

The new source files have to be included into the project. Add in the user_src group the files from the corresponding folder (Right click on the group and select Add – Add Files…). Because a new Main file was included the r_main.c file from the applilet_src group has to be deleted (Right click on the file and select Remove).

Now the debugger driver has to be selected from the project’s options. Right click on the project name and select Options. From the Debugger category choose the TK Debugger Driver.

Now, the project is ready to be compiled and downloaded on the board. Press the F7 key to compile it. Press CTRL + D to download and debug the project.

29 Feb 2012 17:01 · Dragos Bogdan