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Wednesday, July 11, 2007

LED notes



TB029 from microchip.com discusses multiplexing LEDs: TB029

Maxim APP NOTE 1880 from maxim.com: Charlieplexing - Reduced Pin-Count LED Display Multiplexing This application note discusses "Charlieplexing" -- a pin-count reducing multiplex technique used by the MAX6950, MAX6951, MAX6954, MAX6955, MAX6958, and MAX6959 LED display drivers.

Older article about power issues when driving lots of LEDs and a nice explanation of LED multiplexing to save pins: Don Lancaster's Tech Musings August 2001

Maxim APP NOTE 141: Data Multiplexer Adds Cursor To MAX7219 or MAX7221 LED 7 Segment Display Driver Abstract: The MAX7219 or MAX7221 7-segment LED display driver can highlight any one digit of its 8 digit display by adding a data multiplexer. This circuit intensifies the brightness of the selected digit to provide a cursor function for data entry as well as readout.

MAX6956: 2-Wire-Interfaced, 2.5V to 5.5V, 20-Port or 28-Port LED Display Driver and I/O Expander
MAX6956 Programming Guide
Using a Digital Potentiometer for Push-&-Hold Control-Setting Adjustments

Digital Potentiometers Replace Mechanical Potentiometers

Driving 4-1/2 Digit Meter Displays with MAX6958/59 LED Drivers
MAX7219, MAX7221
MAX6950, MAX6951
LED Manufacturers' Web Sites
Maxim Tutorials

I just received a couple sample MAX6969's. "The MAX6969 uses the industry-standard, shift-register-plus- latch-type serial interface. The driver accepts data shifted into a 16-bit shift register using data input DIN and clock input CLK. Input data appears at the DOUT output 16 clock cycles later to allow cascading of multiple MAX6969s. The latch-enable input, LE, loads the 16 bits of shift register data into a 16-bit output latch to set which LEDs are on and which are off. The output enable, OE-bar, gates all 16 outputs on and off, and is fast enough to be used as a PWM input for LED intensity control."

"Multiplexing doubles the MAX6974/MAX6975 drive capability to 48 LEDs."

code and schematic to run 8x8 led grid w/7219 and Arduino

Ok, here's an exact schematic for a 7219 8x8 led matrix and even a pre-made board is available: http://www.woe.onlinehome.de/e_projects.htm



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