Hi, I have a Nokia 5110 display and I was able to wire it up without the use of a level shifter but I was told that I should use one because the display uses 3.3 logic and the arduino is 5. I am using a 4050 shifter.
The schematic I followed for use without the level shifter is here:
The schematic I followed for use with the level shifter is here:
Ive checked my wiring multiple times. Any input would be appreciated 
thanks.
The second diagram is far too difficult to read but, at a guess, it looks like you are feeding signals from an Arduino that is already running off 3.3v and therefore requires no level shifting. In short, you could be sending signals at 2.17v, which is apparently not enough.
It is common practice with 5v Arduinos to run a 5110 off Arduino's 3.3v pin, but not bother about level shifters. I have had some running more or less contiously for several years on 5v Arduinos without level shifting and never had a problem. If you have a setup that works without any level shifting, I suggest you should stick with it.
Thanks for the reply. So to clarrify, your saying it would be safe to connect vcc to the 5v on the arduino? sorry im fairly new to all this.
No. I was talking about using the 3.3v pin on a 5v Arduino. Most Arduinos are 5v, and I believe all of those have a 3.3v pin. More to the point, there is no need for any fancy stuff on the other pins. I now believe you might be using a 5v Arduino, and the 3.3v Arduino in the second link is just for show and adding to the confusion. Either way, connect 5110 vcc to Arduino 3.3v and don't worry about the rest except for the resistor for the backlight, if you need a backlight, which you quite likely don't.
First off. Both of the connection schemes in your OP should work.
I looked at the PCD8544 datasheet. It says:
9 LIMITING VALUES: max VDD = +7V
11 DC CHARACTERISTICS: Logic max VIH HIGH level input voltage = VDD
With VDD connected to 3.3V, this means that the 5V logic will exceed 3.3V by 1.7V.
This clearly "breaks the rules"
There are two possibilities:
a) the 5V logic passes current through the "substrate diodes" to the VDD pin.
b) the logic inputs are tolerant of the VIH <= VDD rule.
So I connected a Nokia display:
VCC (actually VDD) to 3.3V
GND to 0V
CE to 5V via a 10k resistor.
If (a) was true, CE would be about 0.5V higher than VCC. My measurements were 4.86V and 3.25V (nominal 3.3V)
If (b) was true, CE would read 5V. i.e. zero current through the 10k.
My measurements were 4.86V and 4.93V (nominal 5V) i.e. 7uA current
My conclusion:
The PCD8544 is tolerant of "high" VIH values.
The display takes very little current. Even the backlight.
All the same. I always use 3.3V logic with these displays.
TFT controllers are far more critical when it comes to logic voltages.
You MUST limit the voltages to 3.3V. Either with specific buffer chips or series resistors.
Shields from respected companies like Adafruit ensure correct voltages.
Ebay Vendors often lie.
David.
Wow! thanks David. very informative.