Table of Contents
AD7156 - No-OS Driver for Renesas Microcontroller Platforms
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.
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.
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:
|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).|
Renesas RL78G13 Quick Start Guide
This section contains a description of the steps required to run the AD7156 demonstration project on a Renesas RL78G13 platform using the PmodCDC1.
A PmodCDC1 has to be interfaced with the Renesas Demonstration Kit (RDK) for RL78G13:
PmodCDC1 J1 connector Pin SCL → YRDKRL78G13 J11 connector Pin 9 PmodCDC1 J1 connector Pin SDA → YRDKRL78G13 J6 connector Pin 23 PmodCDC1 J1 connector Pin GND → YRDKRL78G13 J11 connector Pin 5 PmodCDC1 J1 connector Pin VCC → YRDKRL78G13 J11 connector Pin 6
Reference Project Overview
The reference project samples the input capacitance on both channels and simultaneously checks if any of the two buttons are pressed or released. The two horizontal bars show how much pressure is applied on the two buttons on the pmod. CH1 has 2pF input range and CH2 has 4pF input range.
Software Project Tutorial
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.
- Run the IAR Embedded Workbench for Renesas RL78 integrated development environment.
- Choose to create a new project (Project – Create New Project).
- Select the RL78 tool chain, the Empty project template and click OK.
- Select a location and a name for the project (ADIEvalBoard for example) and click Save.
- Open the project’s options window (Project – Options).
- From the Target tab of the General Options category select the RL78 – R5F100LE device.
- From the Setup tab of the Debugger category select the TK driver and click OK.
- Extract the files from the lab .zip archive and copy them into the project’s folder.
- The new source files have to be included into the project. Open the Add Files… window (Project – Add Files…), select all the copied files and click open.
- At this moment, all the files are included into the project.
- 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.
- A window will appear asking to configure the emulator. Keep the default settings and press OK.
- To run the project press F5.
Renesas RX63N Quick Start Guide
This section contains a description of the steps required to run the AD7156 demonstration project on a Renesas RX63N platform using the PmodCDC1.
A PmodCDC1 has to be interfaced with the Renesas Demonstration Kit (RDK) for RX63N:
PmodCDC1 J1 connector Pin SCL ? YRDKRX63N JN2 connector Pin 23 PmodCDC1 J1 connector Pin SDA ? YRDKRX63N JN2 connector Pin 22 PmodCDC1 J1 connector Pin GND ? YRDKRX63N J15 connector Pin 5 PmodCDC1 J1 connector Pin VCC ? YRDKRX63N J15 connector Pin 6
Reference Project Overview
The reference project samples the input capacitance on both channels and simultaneously checks if any of the two buttons are pressed or released.
Software Project Setup
This section presents the steps for developing a software application that will run on the Renesas Demo Kit for RX63N for controlling and monitoring the operation of the ADI part.
- Run the High-performance Embedded Workshop integrated development environment.
- A window will appear asking to create or open project workspace. Choose “Create a new project workspace” option and press OK.
- From “Project Types” option select “Application”, name the Workspace and the Project “ADIEvalBoard”, select the “RX” CPU family and “Renesas RX Standard” tool chain. Press OK.
- A few windows will appear asking to configure the project:
- In the “Select Target CPU” window, select “RX600” CPU series, “RX63N” CPU Type and press Next.
- In the first “Option Setting” window change only the Precision of double from single to “Double precision” and press Next.
- In the second “Option Setting” window keep default settings and press Next.
- In the “Setting the Content of Files to be generated” window select ”None” for the ”Generate main() Function” option and press Next.
- In the “Setting the Standard Library” window press “Enable all” and then Next.
- In the “Setting the Stack Area” window check the “Use User Stack” option and press Next.
- In the “Setting the Vector” window keep default settings and press Next.
- In the “Setting the Target System for Debugging” window choose “RX600 Segger J-Link” target and press Next.
- In the “Setting the Debugger Options” and “Changing the Files Name to be created” windows keep default settings, press Next and Finish.
- The workspace is created.
- The RPDL (Renesas Peripheral Driver Library) has to integrated in the project. Unzip the RPDL files (double-click on the file “RPDL_RX63N.exe”). Navigate to where the RPDL files were unpacked and double-click on the “Copy_RPDL_RX63N.bat” to start the copy process. Choose the 100 pins package and little endian option, type the full path where the project was created and after the files were copied, press any key to close the window.
- The new source files have to be included in the project. Use the key sequence Alt, P, A to open the “Add files to project ‘ADIEvalBoard’” window. Double click on the RPDL folder. From the “Files of type” drop-down list, select “C source file (*.C)”. Select all of the files and press Add.
- To avoid conflicts with standard project files remove the files “intprg.c” and “vecttbl.c” which are included in the project. Use the key sequence Alt, P, R to open the “Remove Project Files” window. Select the files, click on Remove and press OK.
- Next the new directory has to be included in the project. Use the key sequence Alt, B, R to open the “RX Standard Toolchain” window. Select the C/C++ tab, select “Show entries for: Include file directories” and press Add. Select “Relative to: Project directory”, type “RPDL” as sub-directory and press OK.
- The library file path has to be added in the project. Select the Link/Library tab, select “Show entries for: Library files” and press Add. Select “Relative to: Project directory”, type “RPDL\RX63N_library” as file path and press OK.
- Because the “intprg.c” file was removed the “PIntPrg” specified in option “start” has to be removed. Change “Category” to “Section”. Press “Edit”, select “PIntPRG” and press “Remove”. From this window the address of each section can be also modified. Set the second address to 0xFFF00000 and the third one to 0xFFF00100. After all the changes are made press OK two times.
- At this point the files extracted from the zip file located in the “Software Tools” section have to be added into the project. Copy all the files from the archive into the project folder.
- Now, the files have to be included in the project. Use the key sequence Alt, P, A to open the “Add files to project ‘ADIEvalBoard’” window. Navigate into ADI folder. From the “Files of type” drop-down list, select “Project Files”. Select all the copied files and press Add.
- Now, the project is ready to be built. Press F7. The message after the Build Process is finished has to be “0 Errors, 0 Warnings”. To run the program on the board, you have to download the firmware into the microprocessor’s memory.
- Example questions:
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