How is the TB6000 setup and wired?
This issue feels like a power problem to me, and I wonder if there isn't an issue with the lcd shield. There is an issue with the backlight wiring on some shields which can cause a high power drain.
Do you have another lcd not on a keypad shield you can use for a test?
You may want to use the hd44780 library instead of the standard LiquidCrystal as it can deal with this issue, and is also faster than the standard library. Use the library manager to install the library, and then this example sketch should run the display on the shield.
// vi:ts=4
// ----------------------------------------------------------------------------
// HelloWorld - simple demonstration of lcd
// Created by Bill Perry 2016-07-02
// bperrybap@opensource.billsworld.billandterrie.com
//
// This example code is unlicensed and is released into the public domain
// ----------------------------------------------------------------------------
//
// This sketch is for LCDs that are directly controlled with Arduino pins.
//
// Sketch prints "Hello, World!" on the lcd
//
// See below for configuring the Arduino pins used.
//
// While not all hd44780 use the same pinout, here is the one that most use:
// pin 1 is the pin closest to the edge of the PCB
// 1 - LCD gnd
// 2 - VCC (5v)
// 3 - Vo Contrast Voltage
// 4 - RS Register Select (rs)
// 5 - Read/Write
// 6 - Enable (en)
// 7 - Data 0 (db0) ----
// 8 - Data 1 (db1) |-------- Not used in 4 bit mode
// 9 - Data 2 (db2) |
// 10 - Data 3 (db3) ----
// 11 - Data 4 (db4)
// 12 - Data 5 (db5)
// 13 - Data 6 (db6)
// 14 - Data 7 (db7)
// 15 - Backlight Anode (+5v)
// 16 - Backlight Cathode (Gnd)
//
// ----------------------------------------------------------------------------
// LiquidCrystal compability:
// Since hd44780 is LiquidCrystal API compatible, most existing LiquidCrystal
// sketches should work with hd44780 hd44780_pinIO i/o class once the
// includes are changed to use hd44780 and the lcd object constructor is
// changed to use the hd44780_pinIO class.
#include <hd44780.h>
#include <hd44780ioClass/hd44780_pinIO.h> // Arduino pin i/o class header
// declare Arduino pins used for LCD functions
// and the lcd object
// Note: this can be with or without backlight control:
// without backlight control:
// The parameters used by hd44780_pinIO are the same as those used by
// the IDE bundled LiquidCrystal library
// note that ESP8266 based arduinos must use the Dn defines rather than
// raw pin numbers.
#if defined (ARDUINO_ARCH_ESP8266)
const int rs=D8, en=D9, db4=D4, db5=D5, db6=D6, db7=D7; // for esp8266 devices
#else
const int rs=8, en=9, db4=4, db5=5, db6=6, db7=7; // for all other devices
#endif
hd44780_pinIO lcd(rs, en, db4, db5, db6, db7);
//with backlight control:
// backlight control requires two additional parameters
// - an additional pin to control the backlight
// - backlight active level which tells the library the level
// needed to turn on the backlight.
// note: If the backlight control pin supports PWM, dimming can be done
// using setBacklight(dimvalue);
//
// WARNING: some lcd keypads have a broken backlight circuit
// If you have a lcd keypad, it is recommended that you first run the
// LCDKeypadCheck sketch to verify that the backlight circuitry
// is ok before enabling backlight control.
// However, the hd44780_PinIO class will autodetect the issue and
// work around it in s/w. If the backlight circuitry is broken,
// dimming will not be possible even if the backlight pin supports PWM.
//
#if defined (ARDUINO_ARCH_ESP8266)
//const int rs=D8, en=D9, db4=D4, db5=D5, db6=D6, db7=D7, bl=D10, blLevel=HIGH;
#else
//const int rs=8, en=9, db4=4, db5=5, db6=6, db7=7, bl=10, blLevel=HIGH;
#endif
//hd44780_pinIO lcd(rs, en, db4, db5, db6, db7, bl, blLevel);
// LCD geometry
const int LCD_COLS = 16;
const int LCD_ROWS = 2;
void setup()
{
// initialize LCD with number of columns and rows:
//
// note:
// begin() will automatically turn on the backlight if backlight
// control is specified in the lcd object constructor
//
lcd.begin(LCD_COLS, LCD_ROWS);
// if backlight control was specified, the backlight should be on now
// Print a message to the LCD
lcd.print("Hello, World!");
}
void loop() {}These are the headers to use with this library and your sketch
#include <hd44780.h>
#include <hd44780ioClass/hd44780_pinIO.h> // Arduino pin i/o class header