Overview

A Feather board without ambition is a Feather board without FeatherWings! Spice up your Feather project with a beautiful 2.4" touchscreen display shield with built in microSD card socket. This TFT display is 2.4" diagonal with a bright 4 white-LED backlight. You get  240x320 pixels with individual 16-bit color pixel control. It has way more resolution than a black and white 128x64 display. As a bonus, this display comes with a resistive touchscreen attached to it already, so you can detect finger presses anywhere on the screen.

This FeatherWing uses a SPI display, touchscreen and SD card socket so it works nice and fast on all our Feathers (including nRF52, ESP8266, 32u4, 328p, M0, M4, WICED and Teensy 3.x) We also include an SPI resistive touchscreen controller so you only need one additional pin to add a high quality touchscreen controller. One more pin is used for an optional SD card that can be used for storing images for display.

This Wing comes fully assembled with dual sockets for your Feather to plug into. You get two sockets per pin so you can plug in wires if you want to connect to Feather pins. Alternatively, each pin has a large square pad on the PCB for direct soldering.

Four mounting holes make it easy to attach this Wing anywhere. We also include a big reset button and an on/off switch connected to the Feather Enable pin (note that the Teensy 3.x Feather does not use the Enable pin so the switch will not do anything with that type).

Pinouts

Unlike most FeatherWings, the TFT FeatherWing is fully assembled and has a dual socket set for your Feather to plug into.

This makes it really easy to use, but a little different to change if you don't want the default setup

Power Pins

All power for the FeatherWing comes from the 3.3V and GND pins. That includes the backlight (which can draw up to 100mA)!

You can turn off the 3.3V power supply with the EN pin or the switch attached to that pin. Note that on the Teensy 3x Feather Adapter, this pin doesn't do anything and on the FONA feather, this will not disable the VBAT power supply which is used to power the cellular module

SPI Pins

The TFT display, SD card and touch screen use the SPI interface to communicate. That means MISO, MOSI and SCK are used whenever either are accessed.

TFT Control Pins

In addition, for the TFT display there is are D/C (Data/Command) and CS (Chip Select) pins. These are used to select the display and tell it what kind of data is being sent. These pins can theoretically be changed by cutting the jumper trace and soldering a small wire from the right-hand pad to the pin you'd like to use.

On the ESP8266, TFT_CS is pin #0, TFT_DC is pin #15

On the ESP32, TFT_CS is pin #15, TFT_DC is pin #33

On theAtmega32u4, ATmega328P, SAMD21 M0, nRF52840 or SAMD51 M4 Feather, TFT_CS is pin #9, TFT_DC is pin #10

On the Teensy Feather, TFT_CS is pin #4, TFT_DC is pin #10

On the WICED Feather, TFT_CS is PA15 and TFT_DC is PB4

On the nRF52832 Feather, TFT_CS is #31 and TFT_DC is #11

There is also LITE pin which is not connected to any pads but you can use to control the backlight. Pull low to turn off the backlight. You can connect it to a PWM output pin.

Note: Pin 9 is used for communication with the SIM800 chip on the Feather Fona. You will have to remap pin 9 to an unused pin when using with a Feather Fona.

Touch Screen control pins

The touch screen also has a Chip Select line, labeled RT. This pin can theoretically be changed by cutting the jumper trance and soldering a small wire from the right-hand pad to the pin you'd like to use.

On the ESP8266, RT is pin #16

On the ESP32, RT is pin #32

On theAtmega32u4, ATmega328P, nRF52840 SAMD21 M0 or SAMD51 M4 Feather, RT is pin #6

On the Teensy Feather, RT is pin #3

On the WICED Feather, RT is PC7

On the nRF52832 Feather, RT is #30

There is also an IRQ pin which is not connected to any pads but you can use to detect when touch events have occured.

SD Card control pins

The SD Card also has a Chip Select line, labeled SD. This pin can theoretically be changed by cutting the jumper trance and soldering a small wire from the right-hand pad to the pin you'd like to use.

On the ESP8266, SD is pin #2

On the ESP32 SD is pin #14

On the Atmega32u4, ATmega328P, nRF52840, SAMD21 M0 or SAMD51 M4 Feather, SD is pin #5

On the Teensy Feather, SD is pin #8

On the WICED Feather, SD is PC5

On the nRF52 Feather, SD is pin #27

There is also an Card Detect (CD) pin which is not connected to any pads but you can use to detect when a microSD card has been inserted have occured. It will be shorted to ground when a card is not inserted.

TFT Graphics Test

The TFT FeatherWing is basically a combination of our 2.4" TFT Breakout with the STMPE610 resistive touch-screen breakout attached.

Install Libraries

You'll need a few libraries to use this FeatherWing!

Install Adafruit ILI9341 TFT Library

We have example code ready to go for use with these TFTs.

From within the Arduino IDE, open up the Library Manager...

Search for ILI9341 and install the Adafruit ILI9341 library that pops up!

Next up, search for Adafruit GFX and locate the core library. A lot of libraries may pop up because we reference it in the description so just make sure you see Adafruit GFX Library in bold at the top.

Install it!

Repeat the search and install steps for the Adafruit_ImageReader and Adafruit_ZeroDMA libraries. That’s four libraries in total.

For more details about this process, we have a tutorial introducing Arduino library concepts and installation.

Basic Graphics Test

After installing these libraries, you should see a new example folder called Adafruit_ILI9341 and inside, an example called graphicstest_featherwing.

Upload that sketch to your Feather. You should see a collection of graphical tests draw out on the TFT.

If you're having difficulties, check the serial console.The first thing the sketch does is read the driver configuration from the TFT, you should see the same numbers as below. That will help you determine if the TFT is found, if not, check your Feather soldering!

Once you've got the demo working, check out the detailed documentation over at http://learn.adafruit.com/adafruit-gfx-graphics-library for more information on how to use the GFX library to draw whatever you like!

Adafruit GFX Library

The Adafruit_GFX library for Arduino provides a common syntax and set of graphics functions for all of our TFT, LCD and OLED displays. This allows Arduino sketches to easily be adapted between display types with minimal fuss…and any new features, performance improvements and bug fixes will immediately apply across our complete offering of color displays.

The GFX library is what lets you draw points, lines, rectangles, round-rects, triangles, text, etc.

Check out our detailed tutorial here http://learn.adafruit.com/adafruit-gfx-graphics-library

It covers the latest and greatest of the GFX library. The GFX library is used in both 8-bit and SPI modes so the underlying commands (drawLine() for example) are identical!

Resistive Touch Screen

The LCD has a 4-wire resistive touch screen glued onto it. You can use this for detecting finger-presses, stylus', etc. Normally, you'll need 4 pins to talk to the touch panel but we decided to go all snazzy and put a dedicated touch screen driver onto the shield. The driver shares the SPI pins with the TFT and SD card, so only one extra pin is needed. This allows you to query the controller when you're ready to read touchscreen data, and saves 3 pins.

To control the touchscreen you'll need one more library - the STMPE610 controller library which does all the low level chatting with the STMPE610 driver chip. Use the library manager to install the Adafruit STMPE610 library

Touchscreen Paint Demo

Now that you've got the basic TFT graphics demo working, let's add in the touchscreen. Run and upload the touchpaint_featherwing demo

  • If you have the 2.4" TFT Featherwing, run the Adafruit ILI9341->touchpaint_featherwing demo
  • If you have the 3.5" TFT Featherwing, run the Adafruit HX8357->touchpaint_featherwing demo

Upload to your Feather and have fun!

The touch screen is made of a thin glass sheet, and its very fragile - a small crack or break will make the entire touch screen unusable. Don't drop or roughly handle the TFT and be especially careful of the corners and edges. When pressing on the touchscreen, sometimes people can use the tip of their fingers, or a fingernail. If you don't find the touchscreen responds well to your fingers, you can use a rounded stylus which will certainly work. Do not press harder and harder until the screen cracks!

Getting data from the touchscreen is fairly straight forward. Start by creating the touchscreen object with

Adafruit_STMPE610 ts = Adafruit_STMPE610(STMPE_CS);

We're using hardware SPI so the clock, mosi and miso pins are not defined here.
Then you can start the touchscreen with

ts.begin()

Check to make sure this returns a True value, which means the driver was found. If it wasn't, make sure you have the Feather soldered right and the correct CS pin!

Now you can call

if (! ts.bufferEmpty())

to check if there's any data in the buffer. The touchscreen driver will store touchpoints at all times. When you're ready to get the data, just check if there's any data in the buffer. If there is, you can call

TS_Point p = ts.getPoint();

To get the oldest point from the buffer. TS_Point has .x .y and .z data points. The x and y points range from 0 to 4095. The STMPE610 does not store any calibration data in it and it doesn't know about rotation. So if you want to rotate the screen you'll need to manually rotate the x/y points! The z point is 'pressure' and ranges from 0 to 255, we don't use it here but you can experiment with it on your own, the harder you press, the lower the number.

Since data from the STMPE610 comes in 0-4095 but our screen is 320 pixels by 240 pixels, we can use map to convert 0-4095 to 0-320 or 0-240. Something like

p.x = map(p.x, 0, 4095, 0, tft.width());
p.y = map(p.y, 0, 4095, 0, tft.height());

However, the touchscreen is a bit bigger than the screen, so we actually need to ignore presses beyond the touchscreen itself. We found that these numbers reflected the true range that overlaps the screen

#define TS_MINX 150
#define TS_MINY 130
#define TS_MAXX 3800
#define TS_MAXY 4000

So we use

p.x = map(p.x, TS_MINX, TS_MAXX, 0, tft.width());
p.y = map(p.y, TS_MINY, TS_MAXY, 0, tft.height());

instead.

One last point (pun intended!) since the touchscreen driver stores points in a buffer, you may want to ask the driver "is the touchscreen being pressed RIGHT NOW?" You can do that with

if (ts.touched())

Drawing Bitmaps

There is a built-in microSD card slot on the FeatherWing, and we can use that to load bitmap images! You will need a microSD card formatted FAT16 or FAT32 (they almost always are by default), and an SD card reader on whatever computer you’re currently reading this with.

Its really easy to draw bitmaps. Lets start by downloading this image of pretty flowers:

feather_purple.bmp
photo by johngineer

Download these two smaller images as well:

The files should be renamed (if needed) to “purple.bmp”, “parrot.bmp” and “wales.bmp”, respectively, and copied to the base directory of the microSD card (not inside a folder).

(If it’s easier, you can also find these images in the “images” folder within the Adafruit_ImageReader library folder.)

Insert the microSD card into the socket in the shield. Now select the sketch file→examples→Adafruit_ImageReader→FeatherWingILI9341 and upload this example to your Feather + Wing. You will see the flowers appear! (Plus parrots…and if you’re using one of the more powerful Feather boards, a whole lot of dragons.)

The Adafruit_ImageReader library, which is being used here to display .BMP images, is fully explained in its own page of the Adafruit_GFX guide.

Troubleshooting

Display does not work on initial power but does work after a reset.

The display driver circuit needs a small amount of time to be ready after initial power. If your code tries to write to the display too soon, it may not be ready. It will work on reset since that typically does not cycle power. If you are having this issue, try adding a small amount of delay before trying to write to the display.

In Arduino, use delay() to add a few milliseconds before calling tft.begin(). Adjust the amount of delay as needed to see how little you can get away with for your specific setup.

Downloads

This guide was first published on Nov 09, 2016. It was last updated on 2019-02-10 14:27:33 -0500.