saving you costs: 4-digit LED display drive using 16f54

[tetsu-jp]

Evolution...

Over the years I tried various methods to drive LED dispplays.

Including:

-resistors in the drive path, and to use a transistor + base resistor for the sink
-using 74hc595 and also 74hc164 serial buffers, without resistors in the drive path
-using digital MOSFET for the sink drive (no gate resistor)
-LCX 244 (74hc255) octal buffer for the sink
-direct PIC drive as you see here

For instance I use LED display for a RAM bootloader module (attachment).
It is built from 2x 74hc595 and 1x lcx244, no resistors, but still quite an effort to wire.
Why have all these extra wires, space, and chips, when they are not needed?

I think the display will at least last a few years. Maybe the lifetime expectation will not be affected at all.

However, such a prototype circuit, with a LED display for debugging, will not be used 24 hours over years. It will be used for some hours during the prototype phase.

When I build prototypes, I try many ideas, when there is improvement, and it is relieable over time, I also use it for future circuits.