>
> "and not Myke's two pin interface... I never had much luck with that"
> What kind of problems did you experience with this implementation?


First of all wiring it compared to a simple shift register is much more
complicated. In the circuit diagram they put all the connections to the
74LS174 next to each other, but in reality you need to connect the lines all
over the place. Also, the diode and resistor increase the number of points
that need to be soldered and designed for on your board even larger.

My second problem with the system is that the "shift" register needs to be
cleared after each operating, which basically doubles the number of cycles
spent shifting. If you just wait for 160us afterwards anyway this doesn't
really matter, of course, but if you're updating the LCD every 160us from an
ISR the double length really impacts the speed of your code.

The third problem is that I never was able to get that E pulse happen quite
the way it is supposed to. Even Myke himself is a bit confused whether it is
high level active or falling edge active. By keeping the enable completely
separate I never ran into problems with this.

Finally, if you keep the enable separate, you can use the shift register
output data for multiple purposes. you just need another enable line, and
you can have the data go to multiple locations, thereby increasing the
number of pins you can output to drastically.

Greetings,
Maarten Hofman.
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