ESP32uesday: Pondering LCDs and Using Espressif DevKits w/Arduino IDE

Last week was a summary (with code) of shenanigans using the ESP32-S3’s LCD controller peripheral for non-LCD applications. That’s all fun and games but it’s time to don big boy pants and use this for actually driving LCDs as intended. Not there yet, but soon.

There are a few good reasons one might want to use this peripheral…versus, say, a typical SPI-connected display…

  • It’s wide (8 or 16 bits) and really, really fast. Fast enough for playing video.
  • Some ESP32-S3 variants have copious amounts of PSRAM…off-chip but closely-coupled memory…which could be used for a massive full-color framebuffer, keeping 100% of internal RAM available for one’s own programming needs.
  • The Adafruit_GFX library was written for (and still supports) the Arduino Uno. It’s always worked well enough for small microcontroller projects, but we’d like to think about what lies ahead now that microcontrollers are no longer small. Projects like LittlevGL provide buttery smooth antialiased graphics, text and user interfaces, and would pair well with highly responsive displays.

Espressif’s ESP-IDF framework includes examples for using the LCD controller as intended. As written, these aren’t for use with the Arduino IDE…but we’ve made some progress in at least compiling there. When possible, we like to have things working with the Arduino IDE as it’s easy for sharing projects among coders still on the learning curve.

Another issue was hardware. The LCD peripheral can work in 8- or 16-bit wide modes (requiring as many data pins), plus several additional control signal lines. An ESP32-S3 Feather might just suffice for 8-bit mode, but eventually I’d like to test this all the way, and there just aren’t enough pins on a Feather board to do this. There are a few ESP32-S3 dev boards that bring out more pins…I opted for Espressif’s own ESP32-S3-DevKitC-1 N8R8 because it has a ton of PSRAM (8 megabytes!), for when I get to that part of the project.

The product page says “there is no Arduino support” but it turns out that’s not strictly true. True, there’s no Arduino “Tools” menu option specifically for Espressif’s DevKit boards, but by selecting “ESP32S3 Dev Module” one can compile and upload code that works…

Some of the fussier Tools options are still a mystery, but haven’t affected the simple test projects I’m starting with. Others, like PSRAM for example…we know the N8R8 DevKit has 8 megs of PSRAM…but do we select “QSPI” or “OPI”? Rooting through the ESP32-S3 WROOM datasheet

…we find that the PSRAM on 8MB modules is “octal SPI” (OSPI or OPI), so we select that for this board…

Bit by bit I’ll puzzle out the other settings as they become necessary…but it won’t be surprising if we see a simple ready-made board selection for this in some future version of the ESP32 Arduino board support package.

Some other things about the DevKit board: in some situations, may want to avoid using GPIO0 (BOOT button), 19 and 20 (used for USB), 35–37 (used for PSRAM) and GPIO48 (used by the onboard NeoPixel). There are impossibly tiny pin numbers silkscreened on the board, but thankfully Espressif has a very legible pinout diagram in their DevKitC-1 User Guide…we’ve included it here at the top of this page. The board schematic may also be helpful.

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