Nokia 5110 display flickering

Other Hardware Displays
1

Hello guys,

I spent my complete day probing and taking everything apart over and over again - I seem not to be able to solve my issue. I have a Nokia 5110 display connected to the SPI pins (using the awesome library here).

The LCD is connected to 3.3V, data pins have a 10k resistor soldered. Everything is working fine. Now, I connected an SD card reader on the SPI bus as well. The display immediately starts to flicker, like old televisions at an incorrect antenna reception: there is a light wave in the middle of the display. As soon as I remove the SD card from the reader the flicker disappears and everything is fine again.

I tried removing all resistors, putting 1k, 4.7k, 10k ones on the SPI cable... nothing seems to work when an SD card is in the reader.

The reader is a Waveshare one, CD is not connected (but tried with 10k pullup-pulldown resistor). LCD is on pins 8-9-10, SD reader is on 5. Board is an Arduino Leonardo.

The symptoms are always present, sample code:

#include <PCD8544_SPI.h>

PCD8544_SPI_FB lcd;

void setup() {
  lcd.begin();
  lcd.clear(0);
  lcd.print("Test");
  lcd.renderAll();
}

void loop () {
}

I know that the good solution is the active level conversion but since I am only supplied with resistors here I would prefer solving it with them.

Any ideas? :slight_smile:

2

aehimself:
As soon as I remove the SD card from the reader the flicker disappears and everything is fine again.

I tried removing all resistors, putting 1k, 4.7k, 10k ones on the SPI cable... nothing seems to work when an SD card is in the reader.
LCD is on pins 8-9-10, SD reader is on 5.
Any ideas? :slight_smile:

Inadequate power?

You talk SPI bus but I would expect you then to be using pins D11,13, and what you are really doing is not clear. It is not necessary to use the SPI bus for the 5110 anyway. I don't think it is necessary to have any resistors.

I recall having a problem rather similar, and also bleed problems. The problems were solved by coming to terms with the fact that these displays are seconds and I suspect not suitable for large fonts or any fancy graphics. I have never seen any need to use anything other than the standard Philips PCD8544 library, but I imagine the Henning Karlsen one would be as good.

3

Hello,

You are absolutely right, there's no need to use the SPI bus. I decided to go this way to free up ports on the board (Leonardo has a separate SPI header, no digital pins used up). Plus, Adafruit's library was too large and slow for my personal satisfaction :slight_smile:

There's one thing I should mention... I tried to put a 10k pullup resistor to the SD card readers Chip Select which made the display almost not to flicker... for the time being. I'll keep it there for a while and put the LCD to a stress test to be sure...

4

OK. I'm not familiar with Leonardo. My 5110 shield uses SPI on Uno but not on Mega. I have never had, or heard of, SD having any bearing on LCD operations, hence my comment about power.