PCB for ESP32 Touchscreen

Printed Circuit board for ESP32 with Touchscreen

This is the next logical step after the “older and solder” touchscreens I have been using for years. ESP32 is a logical upgrade: more power, more GPIO and much simpler HTTPS capabilities. Furthermore several libraries have better versions.

PCB production

Everyone likes soldering, but a few of these onto veroboard is tough.
I decided to draw up a PCB using Fritzing (because I had it) and the last time I made a PCB, it was hand drawn and acid etched in the laundry in 1979. This worked out very well. I simply went to the PCBWay website, filled out a form, uploaded the Gerber files, paid $5 for 10 boards and then a MUCH larger sum for postage!

PCBWay have a kind of real-time monitor where you can “check” on the processes that your boards are going through. This is very entertaining and goes for 24hours.
– Then they post the PCBs to you.
– Then FOUR days later the boards arrive.. in Australia, and they are of a brilliant quality. Uploaded Sunday, and the boards arrived Friday morning. This is a very impressive service!

Electrical

The prototype uses an ESP32 Lolin Lite. This doesn’t have _all_ the GPIO pins but still plenty, but the real advantage is the onboard battery management. It includes a PH2.0 socket so that a typical LiPo 3.7 battery can be used and also charged through the micro USB port.
NB The polarity of this socket is not standard on the ones I have seen. Be careful.

With only 4Mb of memory, it’s still useful and a big sketch can be uploaded with room for OTA updating.

I wire the boards to an ILI9341 2.4″ touch screen as follows.

ESP32 Lolin Lite GPIO	ILI9341 -Screen	ILI9341 -Touch	ILI9341 -SDCard
3.3v	Vcc
Gnd	Gnd
27	CS
26	Reset
14	DC
23	MOSI	T_DIN	SD_MOSI
18	SCK		SD_SCK
13	LED *
19	MISO	T_DO	SD_MISO
18	SCK	T_CLK
15		T_CS
5			SD_CS

User_Setup.h in the TFT_eSPI library can use the standard ILI9341.
You may need to add TOUCH_CS 15

// TFT_eSPI User_Setup for ESP32 Lolin lite and ILI9341 remotes
#define ILI9341_DRIVER       /
#define TFT_CS   27  
#define TFT_DC   14  
#define TFT_RST  26    
#define TOUCH_CS 15

#define LOAD_GLCD   
#define LOAD_FONT2  
#define LOAD_FONT4  
#define LOAD_FONT6  
#define LOAD_FONT7  
#define LOAD_FONT8  /
//#define LOAD_FONT8N 
#define LOAD_GFXFF  
#define SMOOTH_FONT

#define SPI_FREQUENCY  27000000
#define SPI_READ_FREQUENCY  20000000
#define SPI_TOUCH_FREQUENCY  2500000

Note that the ILI9341 LED is connected to GPIO 13 in my example. This is so that the screen can be turned off and on in software.

pinMode(13 , OUTPUT);  // The  pin needs to set to Output 
digitalWrite(13, HIGH); // HIGH - LED/Screen is on

Once again I am using Bodmer’s TFT_eSPI libraries and the TJPGDec.h to display detailed graphics. Not much has changed apart from from obvious inclusions.

#include "SPI.h"
#include "TFT_eSPI.h"
TFT_eSPI tft = TFT_eSPI();
#include <TJpg_Decoder.h>
#include "LittleFS.h" // LittleFS is declared
#include <WiFiManager.h> // https://github.com/tzapu/WiFiManager
#include <ESPmDNS.h>
#include <ESPAsyncWebServer.h>
#include <HTTPClient.h>
#include <ESP32httpUpdate.h>
#include <PubSubClient.h>
#include <Preferences.h>
#include <ArduinoJson.h>
#include "Free_Fonts.h"
#include <elapsedMillis.h>
#include <AsyncElegantOTA.h>
#include "SdFat.h" 

Note some useful additions:

LittleFS	Save and load files to the LittleFS (formerly SPIFFS) memory.
ESPAsynchWebServer	A much more effective webserver for managing files, serving data etc.
SDFat.h
HTTPClient	Especially for calling Homeassistant or PhP scripts to drive devices around the house.
ESP32httpUpdate	Enable OTA firmware updates
AsyncElegantOTA	OTA firmware update interface
PubSubClient	Attach to MQTT server to publish but espcially to get data from sensors, Solar inverter, Air monitors etc.
ArduinoJson	Decode JSON strings from servers

Sample code

For a code example see my post: Coding a Touchscreen Menu !