Matrix Keypad Basic ConnectionThe rows R0 to R3 are connected to Input lines of Microcontroller. The i/opins where they are connected are made Input. This is done by setting the properin AVR and TRIS Register in PIC. The column C0 to C3 are also connectedto MCUs i/o line. These are kept at High Impedance State (AKA input), in highz state (z= impedance) state these pins are neither HIGH or LOW they are inTRISTATE. And in their PORT value we set them all as low, so as soon as we changetheir DDR bit to 1 they become output with value LOW.One by One we make each Column LOW (from high Z state) and read state of R0to R3.
Column 1 SelectedHow to Do it All with AVRsEach i/o port in AVR has three related registers PORTx, DDRx and PINx. Forexample port A has. PORTA Port Driver – when any bit is set to 1 it appearsas HIGH i.e. But this is the case only if that bit is OUTPUT. If it isinput, setting any bit to 1 enables the internal pullup on that bit. DDRA DATA DIRECTION REGISTER– Make any pin on than port as IN or OUT.
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When bit is 1 it represents Output.When bit is 0 it represents Input. Input state is also called tristate orhigh Z state. PINA – Read it to get the level (HIGH or LOW) at the actuali/o pin. It is read when the pin is made input.So now you know. How to make any i/o line Input(high Z) or Output. How to enable internal pullup register on input lines.
How to read value that is present on input lines.Please see the following tutorial for more clarification.Why we make other Columns High Impedance while one column is made LOW?Lets say we selected column number C0, so we make it LOW(i.e. GND or logic0), in the same time we make all other columns high impedance (i.e. Input).If we don’t make other lines high impedance (tristate or Input) they are inoutput mode. And in output mode they must be either LOW(GND or logic 0) or HIGH(5v or logic 1).
We can’t make other lines LOW as we can select only one lineat a time and C0 is already low as per assumption. So the only other possiblestate is all other columns are HIGH.
This is shown in figure below. Red colouron column indicate high state while green is for low state. ATmega32 + LCD + Keypad Interface.We have built the above circuit on a, but it does not has inbuilt LCD Moduleconnector so you need to solder it yourself at the free area (and also do thewiring).Compile the above program using AVR Studio (compiler is avr-gcc). And finallyburn the program using any to the ATmega32. The fuse bits must be set asfollowing to enable external crystal as clock source.
Keypad 4x4 MikroElektronika Keypad 4x4 Keypad 4x4 is used for loading numerics into the microcontroller. It consists of 16 buttons arranged in a form of an array containig four lines and four columns. It is connected to the development system by regular IDC 10 female connector plugged in some development. Martix keypads are well known for their simple architecture and ease of interfacing with any microcontroller. In this part of tutorial we will learn how to interface a 4x4 matrix keypad with AVR and 8051 microcontroller. Also we will see how to program then in Assembly and C. Constructing a Matrix Keypad Constuction of a keypad is really simple.
High Fuse = C9 (hex value). Low fuse =FF (hex value)After burning the HEX file to MCU, finally you are ready to power up the setup.When powered on, the LCD Screen Should show you the keycode of the keypressed on the keypad. This complete our test. Troubleshooting. NO Display on LCD.
Make sure AVR Studio Project is set up for clock frequency of 16MHz(16000000Hz). Adjust the Contrast Adj Pot. Press reset few times. Power On/Off few times. Connect the LCD only as shown on schematic above. No response to key press.
Check that keypad is connected on PORTA only. If you want to attach keypad on different port, change the line 80 onsource code (keypad.c). #define KEYPAD A //KEYPAD IS ATTACHED ON PORTA.
Compiler Errors. Many people these days has jumped to embedded programming without asolid concept of computer science and programming. They don’t know thebasics of compiler and lack experience. To learn basic of compilers andtheir working PC/MAC/Linux( I mean a desktop or laptop) are great platform.But embedded system is not good for learning about compilersand programming basics.
It is for those who already have theseskills and just want to apply it. Make sure all files belonging to the LCD Library are 'added'to the 'Project'. avr-gcc is installed. (The Windows Binary Distribution is called ). The AVR Studio project Type is AVR GCC. General Tips for newbies.
Use ready made and. Try to follow the from the very beginning. (Remember the list spansfour pages, page 1 is most recent addition thus most advance)Video For 4×3 Keypad Interfacing.
User Videos By BrendinI really appreciate Brendin’s approach on getting his problem solved and successfully porting the demo to ATmega48. What I recommend the users is to get your basics strong. You need full understanding of C language concept and the full details of the device you are programming, this will save you lots of time.
So please go and read the good book on C and the datasheet of AVRs before you dive in! – Avinash Downloads.Help Us!We try to publish beginner friendly tutorials for latest subjects in embeddedsystem as fast as we can. If you like these tutorials and they have helped yousolve problems, please help us in return. You can donate any amountas you like securely using a Credit or Debit Card or Paypal.We would be very thankful for your kind help.By Avinash Gupta,Follow on. Great tutorial. Could this be adapted for my atmega48 mcu? I got it working on the atmega48.
I needed to also set the reset pin disable to set PC6 as I/O (this unfortunately means I can no longer program with the ISP programmer). The code works for every button except 2 and 3 (using a 4×3 keypad 2 and 3 are equivalent to 2nd and 3rd button on the top row in this tutorial). When I hold down the 2 button the LCD flashes between 0 and 1 very fast. When I hold down 3 button the same thing happens but flashes between 0 and 2.
All the other buttons work properlyI am not using an external clock. Fuse settings are Low=E2 High=5F and Extended=FFWhat would cause this?thanks,Brendin. I changed some things around and got it working. I put the lcd data on port C and the keypad on port B. Now I don’t have to worry about setting port c6 as an input and disabling reset.
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All of the keys output as expected. Here is a youtube link.Changes I madelcd.h/.LCD CONNECTIONS./#define LCDDATA C//Port PB0 TO PB3 are connected to D4-D7#define LCDE C //Enable/strobe signal#define LCDEPOSPC4// PB4 Position of enable in above portKeypad.c#define KEYPAD B//KEYPAD IS ATTACHED ON PORTA.
@AvinashI understand ur point of view. But if a person has already got a toy car, all opened up then why hesitate in experimenting. If u have time can u atleast tell how can i connect an AtmegaXX to the RF toy car circuit Correct me if i am wrong anywhere.Another question is how can i increase aerial data transfer range if i bought a RF module, for, currently i noe its limited to a modest span of some feet. Cuz elec.mag waves can propagate long distances.Is it achieved with the aid of repeaters (Power Boosting ). And if i dont have repeaters(non commercial experimentation) then how can i increase range of RF module by increasing its Power i/p. Hi Avinash,As Brendin said that to use PC6 as input we have to disable RESET. How can we program AVR in such cases?2.
Whenever, I use PC6 as output, on pressing theRESET switch, how does RESET gets activated,or,what happens internally??? Does it generate somekind of interrpt???3. Somedays ago in a wireless robo-boat championship Isaw that none of the boats were working.All the boats had RF modules attached all of thesame frequency, but DIFFERENT ADDRESS BITS set inthe Rx and Tx. Can you explain? Is it because allof them were trying to work at the same frequency?If yes, Why are address bits provided in Rx and Txmodules using a DIP switch.Thank You in advance. Hi Avinash,Thank you for this great tutorial.
I need your help. I have built the the 4×3 Matrix Keypad Interface – AVR Tutorial using Atmega162.I did not change anything only the microcontroller. I kept the c code as it is. I built it exactly as yours but i am not getting the digit in the LCD as yours. I am getting random keys.My question is the keypad has got 7 pins and could you please help me to find out which one is pin1 to pin7 and which pin is columns and rows.I have buzzed the keypad and I came out with this configuration:ROW1-PIN2-PA0ROW2-PIN7-PA1ROW3-PIN6-PA3ROW4-PIN4-PA4COL1-PIN3-PA6COL2-PIN1-PA5COL3-PIN5-PA4Another question is from other website I have found out that they connect the column with 150 Ohms resistor and the row with 10K to ground, why?Regards,.: hello in the version 1.4.2 is missing under settings the possibility to select the language? Anyone having.: Can you provide this as a complete kit to be soldered by the purchaser?.: can you get more explanation for this example please i have servo motor and a controller with 8MHZ to generate.: Servo Angle 0 degrees require pulse width of 0.388ms(388uS) so value of OCR1A = 388us/4us = 97 how do you get.: Hi Avinash, Today I downloaded extremeburneravrv1.4.2setu p.
Installed it on my laptop.
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