Driving a 2x16 LCD with only One Pin and 74HC595

[Darrel Taylor]

STATUS,C is not a PBP system variable. You can use it.

FOR loops, REPEAT/UNTIL, WHILE/WHEN, DO/LOOP all do not use the system vars (as long as the test condition is = or !=).
They will use system vars if the test condition is <, <=, >, >= etc.

Speed differences between any of the loop types will not be significant on a real chip.
The major slow down with this interface is the timing required to activate inputs on the 595 using the capacitors.
All those delays in the code make writing to the LCD very slow.

[Darrel Taylor]

Your include looks better with the new variable names.
I ran it this morning, and it seems to be working.

Have you looked at the signals going to the 595 on a scope?
Scary stuff to be putting in a digital chip.

Yellow is the serial data.
Blue is after the 1.5K resistor.
Magenta is after the 33K resistor.



And you can see that it takes 910 uS per nibble (1.82 mS per byte).

It would be interesting to see how it works on real hardware.