I do a lot of “Arduino” embedded projects that require a small display for operation. I use small LCDs (16 x 2 to 20 x 4) for this, character or graphical, as they’re rugged, easy to drive, and above all, SMALL. Under 1.5" x 4".
They’re all inherently 5V devices, and most of the useful MCUs are now 3.3V. I’ve been using I2C serial backpacks from Adafruit as they work at 3.3V and up-convert 5V for the LCD. Very nice. (Except DUE; it has known bugs in it’s Wire.h library – yes, in 2023! – that cause it to lock up – not it’s not you. On Due, the Adafruit I2C backpack supports an ersatz bit-banged “SPI” (can’t use hardware SPI) that solves the problem, but the whole thing seems precarious.)
I’d like to eliminate the backpack for many reasons and just run parallel, 3.3V logic. The Hitachi chip will work, but the LCD itself can’t generate the voltage necessary to make contrast work.
I found this discussion on making a negative voltage source for the LCD, applying it on the VO etc pin, and this is easy enough, I’d just add a MAX660 to my board and get software-adjustable contrast out of the deal.
Has anyone done this?
Any suggestions on practical, SMALL, low-overhead character/graphic displays? Adafruit has some small eInk displays, but the how-to page says not to update them more than every two seconds! WTF good is that?!
You must log in or register to comment.
Do a search for the 1.3" 240x240 color TFT display that uses the ST7789 driver. Works on 3.3v, no need for a negative power source, and it has a driver that supports full graphics and multiple fonts. Basically you need four control lines plus the Vcc and ground.
There’s a decent write-up here, but plenty of other sources talk about this display. I have a small handful of them and the output is pretty nice. I’m not sure what the refresh rate is, but I’ve seen some pages in the past showing people playing small video files on it. https://thesolaruniverse.wordpress.com/2019/12/24/connecting-a-240x240-tft-display-with-st7789-controller-with-a-nodemcu-esp8266-or-an-arduino-nano/
Thanks for that – adafruit has one. Will require a redesign for the square shape. Lol, I don’t care what the refresh rate is, can’t be worse than the Hitachi powered LCDs. I do background updates of them so they don’t block, they’re “fast enough” so this will certainly be faster. Gonna buy one and make it work. Thanks again.
Good luck! Based on what you had been working with I wasn’t sure if you preferred the rectangular shape but since I’ve worked with these I thought I would offer it up as a possible solution. A lot of devices have been shifting over to the 3.3v world in the past decade so keep watching, I’m sure more will become available.
Make it a webapp interface, chat gpt may suck with a lot of things but it’s great at web design.
If you design a PCB I bet you could get a backpack in there without sacrificing that much space, but I’m a bit of a noob when it comes to LCD displays and idk your project soo…
There is the option also of finding some random small screen that runs off of serial, only if you aren’t using serial for debugging which is unlikely.
What kind of project is this?
EInk displays are very cool in their specific use cases, but not where the screen need refreshed frequently.
Pros:
- very crisp display. Work great in full sun.
- text usually looks very good on these displays
- 0 power usage when not refreshing the screen.
- display remains as-is even if power is removed. Potentially for hours/days
Cons:
- expensive vs LCD
- refreshing the whole screen can take several seconds
- limited to B&W or sometimes one additional color
- not visible in the dark or in low light.
Some good use cases:
- Price/ID tags
- Thermometer or other slowly changing sensors
- Clocks (without seconds)
