Hello. I have a ST7735S 160x128px 1.8inch RGB LCD and it works well with Arduino, but only at low voltages like 4v. It shows weird glitches at 5v. It has a voltage selecting jumper on it's back and it's set to 5v (it reads open=5v short=3v and mine is open) but somehow this screen does not like 5v. Is my screen broken? If yes, is this can be repaired with a simple process (tell me please)? If no, what is the issue? (Addition: It's onboard voltage regulator works, I measured it.)
Now this issue gets more interesting because I noticed the screen gets really dark at 3.3v but it's backlight is LED and white LED's generally have a running voltage of 3v etc.. As resistors will show the same resistance for all voltages (I was connected a 270r resistor to the LED's), the brightness of the screen should stay roughly the same between 3.3v and 5v but this isn't the fact. What can be caused this?
Here's an image to explain the issue easier:
See 2.4 inch ST7789 TFT SPI display with Arduino boards - Using Arduino / Displays - Arduino Forum
A picture of the backside would reveal that there are no level converters.
@silentobserver Which resistors must be connected to data lines? Are they intended to be a pull-down, or just series to the data lines?
@silentobserver Now I did some calculations and noticed that I will need more than a resistor for lowering the voltages, which way is recommended? And, is just lowering the voltage to 4.5v with a regulator and running the system with this way same? Also, are connections of the SD card (my display contains a builtin SD card input) also 3.3v or are they 5v?
E.g. voltage dividers on the data lines, 2.2k series to 3.3k to GND.
No.
SD cards are 3.3V.
@silentobserver Very excuse me, I mean "is just lowering the voltage to 4.5v with a regulator and running the system with this way safe?" and looks like I accidentally wrote "m" instead of "f"...
You didn't show the backside. But these displays usually have an LDO, a 3.3V series regulator, on the supply line.
So you don't need to reduce the supply voltage.
@silentobserver It has a regulator, but I wasn't mean this. I mean, is driving this display with only lowering the main voltage (not lowering the data voltages) safe (this screen works without problem when I do that)?
Might be safe. You would need to consult the display and controller specs.
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