It wasn't really a thread about shortcuts but I did mention in one or two threads that this is the method I have been using in all commercial and industrial products for many many years. The reason I mentioned it is that many were worried about reading back from a 5V system (LCD) to the 3.3V Prop. The original use of the R/W line many decades ago was to manipulate the data that was held in the LCD module's memory which was appreciable compared to microcomputer's resources of the period. We haven't needed to rely on the scant memory of the LCD for over two decades so the only other reason to read from the LCD is to see if it's busy. It's well documented what the maximum time that the LCD will be busy for on various commands and data so all we have to do is account for that delay in software and avoid reading back from the LCD in which case we can tie the R/W low permanently. Prop interface solved in this case plus this saves one I/O pin. It is also possible to save another pin too if you tie an RC network from one of the data lines down to the RS line and modify the software to precharge the R/S line before strobing data.
PINOUTS
DB7 <--- PROP D0
DB6 <--- PROP D1
DB5 <--- PROP D2
DB4 <--- PROP D3
DB3 NC
DB2 NC
DB1 NC
DB0 NC
E <--- PROP E
R/W --- GND
RS --- PROP RS or PROP Dx via an RC
PINS REQUIRED = 6 or 5
Also keep in mind that the update rate of the lcd is very slow anyway and the longest delay is for the rare 'clear' or 'home' command which is around 1.5ms maximum. Even if you were to slow everything down to this rate you could still update the whole display 10 times a second.
As I said before, I have used this method in scores of commercial and industrial designs for around 20 years. The lcd manufacturers may be stuck in their old original parallel interface and unchallenged "recommendations" and ways but there is no reason that we should follow suit if we have a better way otherwise we may as well be wirewrapping 8080 era CPUs to these LCDs.
mpark
Posts: 1,305
Comments
PINOUTS
DB7 <--- PROP D0
DB6 <--- PROP D1
DB5 <--- PROP D2
DB4 <--- PROP D3
DB3 NC
DB2 NC
DB1 NC
DB0 NC
E <--- PROP E
R/W --- GND
RS --- PROP RS or PROP Dx via an RC
PINS REQUIRED = 6 or 5
Also keep in mind that the update rate of the lcd is very slow anyway and the longest delay is for the rare 'clear' or 'home' command which is around 1.5ms maximum. Even if you were to slow everything down to this rate you could still update the whole display 10 times a second.
As I said before, I have used this method in scores of commercial and industrial designs for around 20 years. The lcd manufacturers may be stuck in their old original parallel interface and unchallenged "recommendations" and ways but there is no reason that we should follow suit if we have a better way otherwise we may as well be wirewrapping 8080 era CPUs to these LCDs.
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*Peter*