“This year I want to tackle some projects that need live data out, so I’ve been sifting through the many display options available for Arduino. Unlike flashier projects, my goal was to find one that I could add to existing logger builds without sacrificing too much of the multi-year lifespan I had worked so hard to achieve. The low power winner by a fair margin was the Nokia 5110 which you can pick up for around $2 from the usual sources. With the back-light off these displays pull between 100-400 μA, depending on the number of pixels turned on.
This screen uses a PCD8544 controller and the SPI protocol. It will tolerate 5V, but it works best at 3.3V, which is perfect when you are driving it from an 8mhz ProMini. Each pixel on the display is represented by a single bit in the PCD8544’s RAM. Each byte in RAM correlates to a vertical column of 8 pixels. The X coordinate works on a per-pixel basis, and accepts values between 0 and 83. The Y coordinate accepts values of 0 – 5 which on this 48 pixel high screen, corresponds to 6 “rows of bytes” in the controller’s RAM. So bitmaps can only be displayed on a per row (& column) basis. The display is quite sluggish compared to competitors like the 0.96 I2C monochrome OLED and you have to handle any processing overhead on the Arduino.
Most hookup guides assume that you can spare six control lines to run the display, which is not the case when your logger already has three indicator LEDs, I2c devices, one wire sensors and a couple of voltage dividers on the go. However if you are willing to add a few resistors and occasionally toggle the power, you can bring that down to three wires and a power pin.
So many libraries, so little optimization…
This screen’s been around for a very long time, so there’s are a huge number of easy to use, highly functional libraries for Arduino. But they tend to focus on things like speed or endless font options which are not important for most data logging applications. And these libs assume your project can afford to lose up to ⅓ of the available program & variable memory just driving the display. Most also require the hardware SPI lines, but our project needs those for SD cards, which are finicky enough without some pokey LCD gumming up the works: the 5110 maxes out at 4mbps, and this significantly slows down the bus.
Those fat libs were non-starters for our project, and I had almost given up on this display when I found Ilett’s Ardutorial offering a bare-bones method more suitable for our resource limited data loggers. If you haven’t discovered Julians YouTube channel yet then you are in for a treat because if Andreas Spiess is the maker worlds answer to Werner Herzog, then Julian is surely their equivalent to Bob Ross. I don’t know if he’s growing “Happy little trees” with his DIY hydroponics, but I can say that the gentle timbre of his “Gooood morning all” reduces stress faster than a warm cup of Tea. And his “Arduino sandwiches” are brilliant examples of minimalist build technique.
Driving the Nokia 5110 with shiftout
Everything I’m presenting here builds on his tutorials, so grab a mug and give ’em a watch:
Tutorial #1 – Connecting and Initial Programming
Tutorial #2 – Getting Text on the Display
Tutorial #3 – Live Numerical Data
This software SPI method (originally from arduino.cc?) requires no library at all, and shiftout commands work with any combination of digital pins; saving those hardware SPI lines for more important jobs.”