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ADXL345 - Microcontroller No-OS Driver

Supported Devices

ADXL345

Evaluation Boards

PmodACL

Overview

The ADXL345 is a small, thin, low power, 3-axis accelerometer with high resolution (13-bit) measurement at up to ±16 g. Digital output data is formatted as 16-bit twos complement and is accessible through either a SPI (3- or 4-wire) or I2C digital interface. The ADXL345 is well suited for mobile device applications. It measures the static acceleration of gravity in tilt-sensing appli-cations, as well as dynamic acceleration resulting from motion or shock. Its high resolution (4 mg/LSB) enables measurement of inclination changes less than 1.0°.

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):

Driver Description

The driver contains two parts:

The driver for the ADXL345 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 ADXL345 driver can be used exactly as it is provided.

If the SPI communication is chosen, there are three functions which are called by the ADXL345 driver:

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

SPI driver architecture

If the I2C communication is chosen, there are three functions which are called by the ADXL345 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 implementation of these three functions depends on the used microcontroller.

The communication protocol has to be chosen in the header file of the Communication Driver.

Example:

#define ADXL345_COMMUNICATION SPI_COMMUNICATION

or

#define ADXL345_COMMUNICATION I2C_COMMUNICATION

The driver for ADXL345 contains functions for reading or writing any of the registers, for placing the device into standby or measure mode, for enable or disable various types of events detection, etc.

The following functions are implemented in this version of ADXL345 driver:

Function	Description
void ADXL345_SetRegisterValue(unsigned char registerAddress, unsigned char registerValue)	Writes data into a register.
unsigned char ADXL345_GetRegisterValue(unsigned char registerAddress)	Reads the value of a register.
unsigned char ADXL345_Init(void)	Initializes the communication peripheral and checks if the ADXL345 part is present.
void ADXL345_SetPowerMode(unsigned char pwrMode)	Places the device into standby/measure mode.
void ADXL345_GetXyz(unsigned short* x, unsigned short* y, unsigned short* z)	Reads the output data of each axis.
void ADXL345_SetTapDetection(unsigned char tapType, unsigned char tapAxes, unsigned char tapDur, unsigned char tapLatent, unsigned char tapWindow, unsigned char tapThresh, unsigned char tapInt)	Enables/disables the tap detection.
void ADXL345_SetActivityDetection(unsigned char actOnOff, unsigned char actAxes, unsigned char actAcDc, unsigned char actThresh, unsigned char actInt)	Enables/disables the activity detection.
void ADXL345_SetInactivityDetection(unsigned char inactOnOff, unsigned char inactAxes, unsigned char inactAcDc, unsigned char inactThresh, unsigned char inactTime, unsigned char inactInt)	Enables/disables the inactivity detection.
void ADXL345_SetFreeFallDetection(unsigned char ffOnOff, unsigned char ffThresh, unsigned char ffTime, unsigned char ffInt)	Enables/disables the free-fall detection.
void ADXL345_SetOffset(unsigned char xOffset, unsigned char yOffset, unsigned char zOffset)	Calibrates the accelerometer.

Downloads

Renesas RL78G13 Quick Start Guide

This section contains a description of the steps required to run the ADXL345 demonstration project on a Renesas RL78G13 platform.

Required Hardware

Renesas Demo Kit for RL78G13 (Renesas)
PmodACL (optional, because an ADXL345 part is installed on Renesas Demonstration Kit (RDK) for RL78G13)

Required Software

Hardware Setup

There are two options:

The ADXL345 part installed on the Renesas Demonstration Kit (RDK) for RL78G13 can be used. In this case, the I2C protocol has to be chosen.

A PmodACL can be connected to the PMOD1 connector. In this case, the SPI protocol has to be chosen.

Software Setup

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

CSI10 (Clocked Serial Interface 10) – For the ST7579 LCD and the ADXL345 part(if the SPI protocol is chosen)

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.

IICA0 (Inter Integrated Circuit Bus) - For the ADXL345 part(if the I2C protocol is chosen)

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.

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

In this example, the output data of each axis is read and displayed on the Renesas Demonstration Kit for RL78G13 board’s LCD. Were also activated “Single Tap”, “Double Tap” and “Free-Fall” interrupts. When one of them occurs, on the LCD screen appears a corresponding message.

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