Floppy Emu uses an 84×48 graphical LCD display. It’s just a low-resolution 1-bit display, but it’s fast and easy to use, and has a nice built-in backlight. The display is actually a clone of the old Nokia 5110 phone display, and it’s made by semi-mysterious third-party factories in Shenzhen. It can be purchased in bulk for about $2.50 apiece. Photo from RH Electronics.
The big problem with these Nokia 5110 displays is that their reliability stinks. The actual LCD module (the glass and metal bit) is clipped onto a supporting PCB with some passive electronics, and it’s only a pressure-fit holding the two together. If it’s not clipped in just right, the display will exhibit contrast problems, or glitchy behavior, or just won’t work at all. Gently pushing on the LCD frame sometimes changes the pressure-fit enough to make these problems appear and disappear. Adjusting and tightening the LCD clips, as described in the Floppy Emu manual, is the only thing I’ve found that helps.
The electronics assembler that builds Floppy Emus must go through every LCD to check for problems. They usually end up discarding about 10% of all the LCDs, because they don’t work no matter how the clips are adjusted. Once the boards are finished, I do a second check of each LCD immediately before it’s shipped to the customer. This often requires more fiddling with the clips, or manual contrast adjustments, and a further 5% of LCDs are discarded. It’s very time-consuming, but despite all this effort, some troublesome LCDs still reach customers who must then make further adjustments.
In the most recent batch of LCDs, the pressure-fit contact design changed slightly, and it now appears to be even more troublesome than before. At the same time, the LCD bezel was unexpectedly enlarged by 2mm, forcing me to redesign the Floppy Emu acrylic case to match. This is a risk of buying generic parts from eBay and Alibaba, with no manufacturer to stand behind them or datasheet to document them.
Surely There Must Be Something Better?
It would be very nice to replace the 5110 displays with something similar but more stable. A replacement would need to handle about 84 x 48 1-bit pixels (equivalent to 21 x 6 text characters), with a diagonal size about 1.5 inches, and ideally use an SPI interface. Unfortunately, I’ve found nothing that even comes close. The alternatives are either much too large/small, lack graphical capabilities, are too slow, or are much too expensive.
Character and numeric displays aren’t appropriate, since they can’t do graphics or six rows of text. So looking at Digikey’s Display Modules – LCD, OLED, Graphic category, and sorting by unit price quantity 100 purchasing, and including only those results that have at least a few hundred units in stock, I found these:
128×128 RGB LCD, 1.44 inch diagonal, $4.23 – This could almost work, except I believe it’s a 24-bit color display, so the microcontroller would need to move 24x as much data to draw on it. And because it’s a much higher resolution, the amount of data to moved must be still higher to maintain the same font sizes as the old display. And it’s a slow I2C interface, instead of fast SPI. And there’s no datasheet.
128×32 LCD, $8.01 – This is an odd shape, doesn’t have enough vertical resolution, and uses a parallel 8-bit interface.
Another 128×32 LCD, $8.69 – Also an odd shape, and not enough vertical resolution.
128×160 RGB LCD, 1.8 inch diagonal, $8.83 – This is another color, higher-resolution display like the $4.23 one, but it uses a parallel interface.
128×64 LCD, 2 inch diagonal, $9.52 – Too big, too expensive, uses a parallel interface.
Non-Branded Options
Nothing from DigiKey looks suitable. What about other options from eBay or Alibaba?
128×64 OLED, 0.96 inch diagonal, $2.91 – This could sort of work, and I have one of these modules already. But it’s tiny, smaller than a postage stamp, which isn’t really suitable. It’s also I2C which means the interface is comparatively slow. Coming from a random non-branded eBay seller, it’s also not clear it would be any more reliable than the LCD display I have now.
128×128 RGB LCD, 1.44 inch diagonal, $3.04 – This is basically the same as the $4.23 module from DigiKey. Although this one says it has an SPI interface. Maybe this is the best option from a list of not-so-great alternatives.
