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Rosie

Why doesn't my LED get any light by using MM5451 LED driver?

1 post in this topic

I'm using an mbed micro controller to switch on all channels on the MM5451 LED driver. I have wired accordingly with 5v PSU, 1k resistor on pin 19 for brightness control (have varied this with no results), data/clock, LEDs with negative to the MM5451 (and positive to +5v inc resistors).

I've got a very basic loop that sends out a string of pulses (35 + start bit) which should switch on all channels, but I'm not getting any light.

 

#include "mbed.h"

DigitalOut dat(p22);
DigitalOut clk(p21);

int main() {
    while(1) {
        wait_ms(500);
        for(int i = 1;i < 37; i++){
            dat = 1;
            wait_us(20);
            clk = 1;
            wait_us(90);
            clk = 0;
            wait_us(20);
            dat = 0;
            wait_us(10);
        }
    }
}

Datasheets:

mbed: NXP LPC1768

Here's an image of the output pulses:

QdMJu.png.e195fd807957fff539d836620cb0c15c.png

Hopefully the chip isn't broken and I'm just making a really stupid error. Looking forward to your answers!

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