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7x5 continued

Added another column of LEDs to my 7x5 board. The columns are connected right on the board. The rows connect slightly above the board, crosswise. I should have moved the first column up also, would have made the next one easier. The next columns should go faster because I can just tie the rows onto the existing leads.

I'm building a 7x5 LED array, row-anode and column-cathode. The columns are connected to PORTD on a Atmel ATTiny2313. I'll use the USART on the '2313 to communicate with the display. I don't think there is enough space on the chip memory for a full character set, so I will probably have to cut back to an application specific set.

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Building a 7x5 LED display

I'm now working on a 7x5 LED display. I use the Atmel ATtiny2313 as a driver. I don't have 35 LEDs of any one color, so I'm building it with stripes of red, yellow, and green LED's. I've got the first column of LED's installed on the circuitboard. I could use this to build a POV device, that might be fun.

The firmware used the Timer/Counter 0 as a clock. Whenever it overflows an interrupt fires. The interrupt advances the row select (r13) and as needed column select (r14). After the interrupt the main loop executes. It writes to PORTB (rows) and PORTD (columns). With the timer running /256 I can watch the LEDs cycle one by one. When I bump the rate up (/1) they are all on.

I wasn't sure how to use PORTD as a column driver, but I figure I'll just keep it set for input (HI-Z state) and just toggle the individual pins to output as needed. Since they will be in a logic low state they can sink the current from the LED.

Applications:

I'm going to use this as the display for my biofeedback project. It will show two or three numbers, then blank for a bit and repeat. I would also like to build a clock using a 7x5 array. Maybe I should buy the next one from SparkFun.com.

LED Matrix (2 Color)

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Constant Current Sink

ucHobby has an article on building and using a Constant Current Sink. I could sure use one of these. I have the necessary parts, I'll probably put one together soon.

Constant Current Sink via uC Hobby.com.

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Biography

Randall Bohn lives in Orem, Utah, USA. He works as a Software Quality Engineer. He is a big fan of the AVR line of microcontrollers. He has been in the computer industry since 1989. Randall is married and has three children.

rsbohn can be reached via gmail.com.


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