Hello,
I have created a pcb using RGB 8x8 leds. I'll refer to the RGB 8x8 LEDs as 'modules'. These modules are controlled via the LED2472GBTR. There are 10 modules, thus, ten LED2472GBTR's.
This is all then controlled via a PIC18F87K22 MCU.
At present, I can display whatever ASCII character I wish. That's not the issue. What I would like to ask about is the ROE/GOE/BOE output enables.
My issue: When applying all three OE channels, if the ASCII character to be displayed upon a module has more than a few 'dots' (or RGB LED's) to light, the colour red seems to dominate. And I don't know why?
Context for my issue:
- I have tried ROE = LOW, then GOE = LOW, then BOW = LOW without delay. Same issue persists.
- I tried the above with a small 1ms delay. Same issue persists.
- The modules are powered via 5V and the LED2472GBTR's are also 5V powered, as is the MCU. I thought, as an experiment, maybe the LED2472GBTR would work better with 3V. SO, set up level shifters and powered the LED2472GBTR's with 3V3. Same issue persists.
- When I program or clear any two of the OE's, whichever leftover colour works. Example: ROE = LOW, GOE & BOE = HIGH. The ASCII character on the modules are red. GOE = LOW, ROE & BOE = HIGH. The ASCII character on the modules are green. BOE = LOW, ROE & GOE = HIGH. The ASCII character on the modules are blue.
- To point 4 above, I can also combine GOE and BOE (both LOW) without ROE (it's HIGH), and get an aqua colour. But as soon as ROE goes LOW, and I guess more than two dots (or RGB LEDs) should be displayed in a ASCII character, then red takes over.
- My modules ASCII character lower-case L ("l"), has two dots horizontally, for 7 of the 8 rows. When I want to display this as white (red+green+blue), I got a white "l". So to me, it seems like if the LED2472GBTR is loaded up too much, it dumps green and blue for red.
So is there any reason why the LED2472GBTR chooses to cut green and blue?
Is there something I am missing? I have followed Figure 8. (Data input time diagram) in Chapter 8 (Digital blocks) from the datasheet.
I have an 18K resistor connected to ISET. And the control registers are not altered upon power-up or reset.
Finally, again, I can get this IC to do what I wish, as far as displaying ASCII characters on my RGB 8x8 modules. But just don't understand what's going on when trying to apply all three colours (Red/Green/Blue) via the OE's.
Thanks
Chris
