LGT8F328P-Displays

!!! under construction !!!

Testing cheap Arduino clones LGT8F328P with the lgt8fx Board Package from dbuezas and the display libraries u8g2 and TFT_eSPI.

Tested Boards

The two tested LGT8F328P Boards and the original Arduino Boards :

More information :

• https://github.com/dbuezas/lgt8fx
• https://github.com/wollewald/lgt8fx
• https://wolles-elektronikkiste.de/minievb-boards-ein-ueberblick
• https://wolles-elektronikkiste.de/lgt8f328p-lqfp32-boards

Quick installation

• Install lgt8fx Board Package : https://github.com/dbuezas/lgt8fx
• Install the libraries "u8g2" and "TFT_eSPI".
• Copy the program file(s) from the folder "Arduino" and especially "Arduino/libraries", which contain all configuration files and the modified TFT_eSPI_Generic.h.
• Test u8g2 : u8g2_GraphicsTest.ino
• Test TFT_eSPI : TFT_eSPI_graphicstest_small_touch.ino

u8g2-Library and Display GMG12864-06D

Test with LGT8F328P LQFP48 "Nano" and Display GMG12864-06D.

Also tested with the LGT8F328P LQFP32 "Pro Mini" 3.3V and USB-TTL-Adapter (see below). Works fine and very fast.

Connections for LCD Display GMG12864-06D :

TFT	GPIO	Description
SI	11	SPI MOSI
SCL	13	SPI SCLK
CS	7	CS
RS	8	DC
RSE	RST	RESET Pin
VDD		3.3V (5V)
VSS		GND
A		LED A -> 47Ω -> 3.3V (5V)
K		LED K -> GND

The display can be used with 3,3V or 5V. In this test i used a 3.3V voltage regulator for VSS and backlight LED.

Configuration of the u8g2 library in u8g2_GraphicsTest.ino:

#include <Arduino.h>
#include <U8g2lib.h>

#ifdef U8X8_HAVE_HW_SPI
#include <SPI.h>         // uses the SPI-library of the lgt8fx Board Package
#endif
#ifdef U8X8_HAVE_HW_I2C
#include <Wire.h>
#endif

// Hardware-SPI
U8G2_ST7565_ERC12864_ALT_F_4W_HW_SPI u8g2(U8G2_R0, /* cs=*/ 7, /* dc=*/ 8, /* reset=*/ U8X8_PIN_NONE);

#define CONTRAST 75      // don't forget, to set the contrast!

void setup(void) {
  u8g2.begin();
  u8g2.setContrast(CONTRAST); 
}

void loop(void) {
  //...
}  

TFT_eSPI-Library and 1.8" Touch-Display ST7735 (128x160).

Test with the LGT8F328P LQFP36 "Mini Pro" 3.3V and USB-TTL-Adapter.

Display and touch work fine with modification of TFT_eSPI\Processors\TFT_eSPI_Generic.h (see below).

Connections for 1.8" Touch-Display ST7735 :

GPIO	TFT	Touch	SD-Card	Description
11	SDA	T_DIN	SD_MOSI	MOSI
12		T_DO	SD_MISO	MISO
13	SCK	T-CLK	SD_SCK	CLK
8	A0			DC
RST	RESET			RST
7	CS			CS-TFT
4		T_CS		CS-Touch
			SD_CS	CS-SD (not used)
		T_IRQ		IRQ (not used)
	GND			GND
	VCC			3.3V
	LED			3.3V

The modification of TFT_eSPI\Processors\TFT_eSPI_Generic.h :

Replaced :

...   
    #ifdef __AVR__ // AVR processors do not have 16 bit transfer
      #define tft_Write_8(C)   {SPDR=(C); while (!(SPSR&_BV(SPIF)));}
...      

with :

...
    #ifdef __AVR__ // AVR processors do not have 16 bit transfer
      #ifdef __LGT8FX8P__
        #define tft_Write_8(C)   {SPDR=(C); asm volatile("nop"); while((SPFR & _BV(RDEMPT))); SPFR=_BV(RDEMPT)|_BV(WREMPT); }
      #else
        #define tft_Write_8(C)   {SPDR=(C); while (!(SPSR&_BV(SPIF)));}
      #endif  
...

Solution found here :

• https://github.com/dbuezas/lgt8fx/blob/master/lgt8f/libraries/SPI/src/SPI.h
• https://github.com/adafruit/Adafruit-GFX-Library/pull/313/commits/14aa943754aac8825e75f9ff75c308bf7ada7ab4

SPI-Transfer for AVR and LGT8FX8P in SPI.h :

inline static uint8_t transfer(uint8_t data) {
  uint8_t rcvd;
	  
  SPDR = data;
  asm volatile("nop");
  #if defined(__LGT8FX8P__)
    while((SPFR & _BV(RDEMPT)));
    rcvd = SPDR;
    SPFR = _BV(RDEMPT) | _BV(WREMPT);
  #else
    while(!(SPSR & _BV(SPIF)));
    rcvd = SPDR;
  #endif

  return rcvd;
}