Connecting ESP8266 with ILI9341 TFT Display

Posted on Fri 04 March 2016 in misc View Comments

ESP8266 was popular with hobbyists for a long time. Recently I decided to join the hype and bought this module along with a super cheap color TFT display (ILI9341). In this post I will describe the process of connecting those two, using already available code written for Arduino.

ESP8288 connected to ILI9341

First step is to set up Arduino IDE to work with ESP8266.

There is an excellent tutorial on Sparkfun's website that explains how to do this.

Once Arduino IDE is setup, you need to get the Adafruit ILI9341 library. Currently version 1.0.1 is available through Arduino IDE's "manage libraries" interface. Unfortunately this version is broken for ESP8266.

Until this is fixed, you have to get it directly from the Adafruit repository. One can git clone it or download the zip. Put it into the arduino library folder. The exact location is OS and IDE version depndent.

After this, fire up the IDE. If previous step was performed correctly, Under the file->examples sub-menu you should be able to see Adafruit ILI9341 menu. Choose the graphicstest example and try to compile it. If it compiles fine, you are ready for wiring.

Wiring is a bit tricky. First look at the diagram of the nodemcu v3 board:

nodemcu v3 lolin

Make the following connections:

ILI9341 ESP8266
SDD/MISO D6
LED 3.3V
SCK D5
SDI/MOSI D7
DC/RS D1
RESET 3.3V
CS D2
GND GND
VCC 3.3V

Make sure you connect all display's pins. Some tutorials do not mention RESET and LED pins and it took me some time to figure out that these can not be left floating.

Now you need to alter the example sketch to reflect the fact that we chose D1 and D2 for CS and DC. Edit the configuration lines to be:

// For the Adafruit shield, these are the default.
#define TFT_DC D1
#define TFT_CS D2

Now connect the board to the computer, build and upload. You should be able to see a a test pattern start running on the TFT screen.

Unfortunately, at some point the test pattern will freeze or even reset the device before the program completes the execution.

If you open serial monitor, you will see something like this:

���ԅu�D�ILI9341 Test!
Display Power Mode: 0x9C
MADCTL Mode: 0x48
Pixel Format: 0x5
Image Format: 0x0
Self Diagnostic: 0xC0
Benchmark                Time (microseconds)
Screen fill              2259125
Text                     161736
Lines                    
Soft WDT reset

ctx: cont 
sp: 3ffef8d0 end: 3ffefbd0 offset: 01b0

>>>stack>>>
3ffefa80:  016e3600 00000001 3ffeea58 000007e0  
3ffefa90:  00000080 00000008 3ffeea58 402032f8  
3ffefaa0:  3ffeea9c 00000001 3ffeea58 0000006c  
3ffefab0:  0000006d 0000002a 3ffeea58 40203378  
3ffefac0:  3ffeea9c 000000f6 3ffeea58 402037b2  
3ffefad0:  000000f7 000000f6 3ffeea9c 402027ab  
3ffefae0:  016e3600 00000001 3ffeea58 000007ff  
3ffefaf0:  0000006c 000000f6 3ffeea58 40203876  
3ffefb00:  016e3600 00000001 3ffeeb7c 00000000  
3ffefb10:  00000000 000000f0 3ffeea58 000000ef  
3ffefb20:  0000006c 000000ef 0000005f 402046e1  
3ffefb30:  00000000 00000001 000007ff 00000085  
3ffefb40:  3ffeea58 000000f6 402044b8 00000144  
3ffefb50:  000000f0 000007ff 3ffeea58 00cb82d4  
3ffefb60:  000000ba 000007ff 3ffeea58 40201c40  
3ffefb70:  0000013f 000000ef 00000140 000000ef  
3ffefb80:  000000ef 3ffeeba8 402044b8 3ffeebb0  
3ffefb90:  3ffeeb7c 00000018 4022d52d 3ffeeba8  
3ffefba0:  00000000 000000c0 3ffeeb7c 40202398  
3ffefbb0:  3fffdc20 00000000 3ffeeba0 402044f6  
3ffefbc0:  00000000 00000000 3ffeebb0 40100114  
<<<stack<<<

The problem here is that ESP8266 has a watchdog set to one second. The lines test pattern takes longer than one second to execute and therefore the watchdog resets the processor.

The ILI9341 example is already "feeding" the watchdog using the yield(); call. Unfortunately, on the ESP8266, some code between the yield(); calls still takes more than one seconds (this code was written with Arduino in mind). To make this example run, you will have to add additional yield(); calls. Use trial and error method to figure out where to add those.

Disabling the watchdog is also a viable options, but I was not able to figure out how to do it. If you find a way to do this, write me through the comments.

ILI9341 example running