Category Archives: Code Libraries


Time Input Dialog for Graphic LCD

GUI Frameworks of all modern OS like Windows, Linux (Qt & GTK+), MAC etc have a concept of standard dialogs. For example all applications running under Windows shows the same file open dialog for selecting a file. Similarly their are standard dialogs for folder selection, colour selection, font selection etc. This concept has several advantages, and the most important is a easy user interface. Since the user is already familiar with file selection in one application, he/she can use file open dialog of any application. Building on the same concept our GUI framework for ProGFX (avr glcd driver) will too have many standard dialogs for common user interface. In this tutorial we will build the "Time Input Dialog" that helps programmer ask the user to input time. The time could be anything like :- "On" or "Off" time for a relay in a timer application. Alarm time in an alarm clock application. Period start time in a school bell application. And many others. The programmer just need to call the function. void ShowGetTimeDlg(uint8_t *h,uint8_t *m,uint8_t *s,uint8_t *am_pm) It takes four parameters hour, minutes, second and am_pm. All parameters are passed by reference(pointer actually), this is because the function modifies the value of those variables. It shows a dialog as shown below :- Time Input Dialog The user can use the […]


DS1307 I2C RTCC Interface using SoftI2C lib

In the last tutorial, I explained you how to use our SoftI2C library to read and write a 24CXX series I2C EEPROM. Now I will continue our exploration and write a register access layer for the DS1307 chip. The DS1307 chip is a real time clock and calendar IC. The register access layer that we will develop provides the application programmer with function that reads and write the registers of DS1307. Remember that any piece of hardware appears to the CPU as a set of registers only. DS1307 has :- Seven Registers (from 0×00 to 0×06) that are used for timekeeping functions. One CONTROL register(0×07) for square wave generation setting (we don’t use this for simplicity). 56 bytes of battery backup RAM (from 0×08 to 0x3F) Fig. : A Simple DS1307 RTC Module.   Once the application programmer has access to functions that reads and writes to any register (specified by its address) inside DS1307 ic, he/she can easily get and set the time infos like sec,min,hour, am/pm, date,month,year etc. The register access layer is built over the core Soft I2C layer. The register access layer consists of the following three functions. void DS1307Init(void) { SoftI2CInit(); } /*************************************************** Function To Read Internal Registers of DS1307 ——————————————— address : Address of the register data: value of register is copied to this. […]

24C1024 I2C EEPROM 128KB

24CXX I2C EEPROM Interface using SoftI2C lib

In this tutorial I will show you how to use our easy to use open source Soft I2C library to access a 24C64 EEPROM chip. We discussed the library in our previous tutorial. The functions developed in this tutorial will use services of the I2C library to read and write the EEPROM. The EEPROM access mainly contains only two routines. BOOL EEWriteByte(uint16_t address,uint8_t data); BOOL EEReadByte(uint16_t address ,uint8_t* data); The first one write a 8 bit data to a memory location specified by the variable address, since a EEPROM can have more that 256 bytes of storage that is why the address variable is 16 bit. The second function reads the memory location specified by the variable address and stores the read data in variable data. Both the function return EE_SUCCESS on success and EE_IO_ERROR on failure. How to develop the EEPROM Write function? We open the datasheet of 24C64A (64kbit) EEPROM and try to understand the random read and random write function. The figure 8 on page number 11 clearly describes the write steps. You just need to translate the figure into proper call to our Soft I2C lib API’s. BOOL EEWriteByte(uint16_t address,uint8_t data) { SoftI2CStart(); //SLA+W if(!SoftI2CWriteByte(EEPROM_WRITE_ADDRESS)) { SoftI2CStop(); //I2C i/o error return EE_IO_ERROR; } //Address HIGH if(!SoftI2CWriteByte(address>>8)) { SoftI2CStop(); //I2C i/o error return EE_IO_ERROR; } //Address LOW […]


Software I2C Library for AVR MCUs

Inter IC Communication or I2C is a two wire serial communication bus used to connect a variety of external peripheral with a microcontroller. Most common are EEPROMs, RTC, Port Expanders etc. Most leading MCUs comes with at least one dedicated I2C host adaptor built in. But some times we need more than one I2C interface or we need I2C lines on some other i/o pins than those allotted to the hardware I2C, in that case we need to go with a solution called SoftI2C. In SoftI2C the I2C signals are handled in software, the advantage is that any two i/o line of the MCU can be used for communication. The drawback is that it need more CPU cycles are wasted in generating the signal thus less time slice is available to the application. In this article we will present our open source, flexible and easy to use SoftI2C library. This library can be used to connect any I2C slave device with an AVR (and latter PIC MCU) MCU. Some limitations of the library are :- No Multimaster support. No clock stretching support. But you can connect multiple number of I2C Slaves on the same bus. I2C Master/Slave Connection The Soft I2C Library for AVR The soft I2C library for AVR comes in two files. i2csoft.c i2csoft.h The configuration section lets […]

Using Shift Registers with AVR Micro – AVR Tutorial

Today I am going to explain a helpful technique used while designing embedded system. The technique is to expand the number of input and output lines available in any microcontroller. The idea is to use a shift register, a shift register help us load data in a serial fashion (requiring less number of i/o lines) and then convert the data into a parallel form that can drive many types of load like LED,Relays, motor etc, just like normal i/o ports of MCU. Their are two advantage of this method:- Only three i/o lines can drive virtually any number of output ports. Say if you want to control 50 leds that are at the distance of 2 meter from the controller then you save lots of wires! and mess up too! The above described what we called an output shift register. Another type is an input shift register. This type is used to take input. It does reverse of the output shift register. It takes parallel input and transfer it serially to the MCU. The most common commercial example I found is the NES joystick. Their are 8 buttons (you will notice 10 but 2 of it are turbo, that means they repeat action A or B(turbo A or B pressed) at particular frequency when kept depressed) The designers didn’t ran […]

Interfacing KS0108 based 128×64 Graphical LCD with AVR MCU.

Those how are building microcontroller based project for little long must have got bored with the good old character LCDs. Whether you are bored or your application require to present more data to the user in a better way, you need Graphic LCD. Character LCD Interfacing is quite easy so every one uses it, but when I comes to Graphic LCD you need a well written and powerful graphic library. Its not enough that you read the LCD datasheet and connect it your MCU and start sending data. Because the LCD just appears to be block of memory whose contents are directly visible on screen. The datasheet can only guide you how to access this memory. You just can’t do much by writing to the memory. The graphic library is a piece of software that has complex algorithms to render graphic primitives like line, rectangles, circles, images and more. It also helps load fonts and render text and numbers on screen. So it provide high level access to the LCD screen and applications can be written much more easily. While I was researching for graphic library for the GLCDs, I found some but I was not fully satisfied by any of them. So I began to write a clean, powerful, portable and easy to use library that can handle sever […]

Interfacing 12 bit SPI ADC (MCP3204) with AVR Micro

Hello All, Sometimes the Internal ADC is not enough. Like when you need more resolution or high speed. The internal ADC of AVR generally has the following specifications. 15K samples per second 10 bit resolution. If you need more than that you need an external ADC. You may also need external ADCs if you have already used the internal ones. This tutorial will guide you how to install an external ADC with AVR MCU and write a test program to get data from it. A very common external ADC is from Microchip the MCP3204. It has the following configuration. 100K samples per second. (More than 6 times faster than AVRs inbuilt) 12 bit resolution (4 times more detailed) 4 input channels (MCP3208 has 8 channels). SPI Bus Compatible. Basic SPI Tutorial These ADCs are SPI Bus based which is a serial bus. So the number of pins in IC is very low. Total of 4 lines are required to interface it with AVR MCU. MISO (Master In Slave Out) MOSI (Master Out Slave In) SCK (Serial Clock) CS (Chip Select) As you know in synchronous serial communication their is a clock line (SCK in case of SPI) which synchronizes the transfer. Please read the article :- Synchronous Serial Communication Tutorial – The Basics of I2C and SPI. The clock is […]

Interfacing DS1307 RTC Chip with AVR Microcontroller

Real Time Clocks, as the name suggests are clock modules. They are available as integrated circuits (ICs) and manages timing like a clock. Some RTC ICs also manages date like a calendar. The main advantage is that they have a system of battery backup which keeps the clock/ca lender running even in case of power failure. A very small current is required for keeping the RTC alive. This in most case is provided by a miniature 3v lithium coin cell. So even if the embedded system with RTC is powered off the RTC module is up and running by the backup cell. This same technique is used in PC timing also. If you have opened your computer case you will notice a small coin cell in the mother board. In this tutorial we will learn to use a very famous RTC IC named DS1307. The DS1307 is described in the datasheet as follows The DS1307 is a low-power clock/calendar with 56 bytes of battery-backed SRAM. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The DS1307 operates as a slave device on the I2C bus. So the aim of the project will be to […]

Easy 24C I2C Serial EEPROM Interfacing with AVR Microcontrollers

In this turorial we will see how we can easily interface a 24C series serial EEPROM with AVR microcontrollers. What is an EEPROM? An EEPROM is kinds of novalatile memory, that means it is used for storing digital data permanently without any power suply. EEPROM stands for Electrically Erasable Programmable Read Only Memory. The advantage of these kind of ROMs is that they can be erased Electrically to make them ready for storing new data. Compare this with a CD R disks they can be recorded only once. A small amount of EEPROM is also available internally on the AVR chips. So if the volume of data you want to store is small (say few user names and password) then you can use it. The internal eeprom makes design small and simple. But if the amount of data you want to store is large, say in order of few tens of kilobytes then you have to interface a External EEPROM chip with your AVR MCU. You can store pictures, sound and long texts in these eeproms. Their are many kinds of EEPROM chip available from many manufactures. One very common family is 24C series serial EEPROMs. They are available upto 128KB in size. They uses I2C interface with host controller (MCU) which is a very popular serial communication standard. I […]

Using the USART of AVR Microcontrollers : Reading and Writing Data

Till now we have seen the basics of RS232 communication, the function of level converter and the internal USART of AVR micro. After understanding the USART of AVR we have also written a easy to use function to initialize the USART. That was the first step to use RS232. Now we will see how we can actually send/receive data via rs232. As this tutorial is intended for those who are never used USART we will keep the things simple so as to just concentrate on the "USART" part. Of course after you are comfortable with usart you can make it more usable my using interrupt driven mechanism rather than "polling" the usart. So lets get started! In this section we will make two functions :- USARTReadChar() : To read the data (char) from the USART buffer. USARTWriteChar(): To write a given data (char) to the USART. This two functions will demonstrate the use of USART in the most basic and simplest way. After that you can easily write functions that can write strings to USART. Reading From The USART : USARTReadChar() Function. This function will help you read data from the USART. For example if you use your PC to send data to your micro the data is automatically received by the USART of AVR and put in a buffer […]

Using IR remote with AVR MCUs – Part II

Hello Friends, Welcome back. In previous tutorial I introduced my IR remote decoding library. In this tutorial I will continue our discussion and show you how to add IR remote controls support to your AVR projects. Step I Download the library files and unzip them in a folder. Step II In AVR studio create a new AVR-GCC project. Then copy the following files to the project folder. IR remote related. Source Files remote.c Header Files remote.h rckeys.h LCD Related Source Files lcd.c Header Files lcd.h myutils.h Note: Include file from the \lib\ATmega8 if you are using ATmega8 \lib\ATmega16 if you are using ATmega16 or ATmega32 After The files have been copied add them to your project by right clicking project view and selecting “Add Existing Source File(s)…” and then select the “lcd.c”. Similarly add other source files. In the same way add the header files by selecting "Add Existing Header File(s)…" Adding files to projects.   If instead of AVR Studio you use Makefiles then add all the source files names in the source section of the makefile along with your main c file (which has same name as your project and has the main function). Step III. In your main C source file include the following files #include "remote.h" in addition to standard files in your main() function initialize […]