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Standard Commands for Serial Displays?


New member
I am using a PICAXE 18X and a Crystalfontz 2X20 parallel input display to make my own serial display. I would like to use standard commands if they exist. But after reading data sheets from several manufacturers, including Crystanfontz, I am not seeing any pattern. Is there any command set that is fairly standard or is it just every manufacturer for himself? Is there any that are more popular to the poing of being semi standard?
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New member
Thanks Tech.

One more question. I am presently building my board and need to determine how to connect the background LED. I am using a 2 X 20 parallel display (CFAH2002AYMIJP) and have +9 unregulated and +5 regulated supplies available without extra work. In your data sheet, I read that it wants MAXIMUMS OF 4.2 Volts and 210 mA. I know that LEDs usually use resistors for current limiting but many have built in resistors or whatever. What is my best scheme using my available voltages and why? Do your displays have internal resistors or other current limiting devices?

I think your data sheet could be improved in this area.


CF Tech

LEDs are "current" devices. You need to limit the current through them. Ideally, a current source would be used. You can use a resistor though. The second post of this thread tells how to calculate the resistor's value.


We are working on improving our data sheets, but there are many to update. For instance on page 17 of this data sheet there are more detailed instructions on driving the LED backlight: