Debug LEDs

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Want some collection of LEDs to aid in debugging/act as status indicators

At a minimum, I will want:

1. Power LED
2. Heartbeat LED
3. Scopes/Interface/Status LED (maybe with colour?)
4. Scopes/Interface/TX and RX LEDs

How do I plan on driving these?

• Ideally I want these to be as simple as possible (ie directly to a GPIO, rather than through even an IO expander like a shift register)
• This is to make debugging as easy as possible/as informative as possible—the LED will come on as soon as I toggle the GPIO
• This is the advantage of dedicated debug/status LEDs, rather than using some subset of the display
• Perhaps I can use the left-over bits in the shift registers/LED drivers?
• Maybe have some direct-debug LEDs/test points, and some more 'complex' full-colour LEDs routed through the spare bits in the display layout?
• Regarding using spare bits in the shift registers—this would not work with my preferred direct-chaining approach, as I am assuming that only a single row (and hence a single output across all shift registers) is active at any given time—using one of the unused bits for a status LED would not work.
• I could potentially use the 5 unused output groups in my LED drivers however, and leave the common anodes permanently tied to —this is fine, as I would not be multiplexing the status LED. This would only incur extra firmware/routing complexity, but could be considered.

Do I want them to be single-colour, or RGB?

• If they are RGB, I can reuse the same BOM component as for my matrix—part consolidation & order quantity advantages
• But, if they are RGB, then they will require more data lines (if I want a simple drive method)
• I will also need individual current-limiting resistors, and I will only be able to produce the few colour permutations of pure R/G/B (unless I use PWM)
• Alternatively, I can use addressable LEDs for my status LEDs?
• If I use a single-colour LED, I only require a single GPIO pin
• But I will need to have a whole extra part number