Since the Nokia 5110 LCD is a 3.3 V device, i need to shift the logic level, in addition to the supply voltage level to 3.3 V from 5 V coming from the UNO. I read in my online research that i could simply use resistors in series.
How to calculate the value of each resistor for the series connection? The LCD has 8 pins.
Why are the resistors connected in series if it's for a voltage divider? But in most online guides, i've seen resistors connected in series between each pin from the UNO to the LCD.
Like i said over there, i'm trying to get multiple opinions as there might be different answers or ideas. But if it's against the policy or something, i can delete it from here or arduino forums.
You can power the 5110 from Arduino 3.3v pin. The other pins are 5v tolerant. Not all 5110s are the same and sometimes the backlight has to be wired to ground.
DryRun:
Like i said over there, i'm trying to get multiple opinions as there might be different answers or ideas. But if it's against the policy or something, i can delete it from here or arduino forums.
It's not against policy to post the same question on multiple sites, but if you're going to do that please post a link from each to the other. That way we can avoid wasting time asking for clarification or giving an answer when that information is already on the other post. It will also make sure that anyone else with the same question who finds this thread will be able to easily get all the relevant information.
Nick_Pyner:
You can power the 5110 from Arduino 3.3v pin. The other pins are 5v tolerant. Not all 5110s are the same and sometimes the backlight has to be wired to ground.
OK, i checked mine and it has no mentioned anywhere on the silk screen about the voltage. So, to be safe, i will set all the pins to 3.3 V.
I did more digging on the matter and i found that some sites are suggesting connecting 10 KOhms in series with the pins. How did they end up with that resistor value??
pert:
It's not against policy to post the same question on multiple sites, but if you're going to do that please post a link from each to the other. That way we can avoid wasting time asking for clarification or giving an answer when that information is already on the other post. It will also make sure that anyone else with the same question who finds this thread will be able to easily get all the relevant information.
sterretje:
10k is just to limit the current that can flow through the pins; some kind of magic thumb suck.
Sparkfun has an article about the wiring; if I'm not mistaken, it has some explanations as well.
OK, so, the resistors will limit the current, but what about the voltage? Does that mean that the 5 V from the Arduino pins will still prevail at the LCD pins?
One of the cheap and easiest way to shift levels is to add resistors inline with each data transmission pin. Just add 10kΩ resistors between the CLK, DIN, D/C, and RST pins and a 1kΩ resistor between CE.
