I looked at the I2C 20X4 board at
DFRobot and DFRobot, in the spirit of open source, provides a schematic (floresta, thanks for the tip). Based on DFRobot, the back side of the SainSmart board must not only contain a resistor, but also a transistor. The SDA/SCL lines do not have pull-up resistors, as anticipated - but it works, nonetheless. DFRobot provides their own LiquidCrystal library which contains the LiquidCrystal_I2C routines. I did not test their code against their library (
I'll just assume that it works). I did modify their example code to work with F Malpartida's NewLiquidCrystal library and it functions well. Their modified example is:
//DFRobot.com
//Compatible with the Arduino IDE 1.0
//Library version:1.1
#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h> // F Malpartida's NewLiquidCrystal library
#define I2C_ADDR 0x27 // Define PCF8574A's I2C Address
#define BACKLIGHT_PIN 3
#define En_pin 2
#define Rw_pin 1
#define Rs_pin 0
#define D4_pin 4
#define D5_pin 5
#define D6_pin 6
#define D7_pin 7
#define LED_OFF 0
#define LED_ON 1
#define printByte(args) write(args);
uint8_t bell[8] = {0x4,0xe,0xe,0xe,0x1f,0x0,0x4};
uint8_t note[8] = {0x2,0x3,0x2,0xe,0x1e,0xc,0x0};
uint8_t clock[8] = {0x0,0xe,0x15,0x17,0x11,0xe,0x0};
uint8_t heart[8] = {0x0,0xa,0x1f,0x1f,0xe,0x4,0x0};
uint8_t duck[8] = {0x0,0xc,0x1d,0xf,0xf,0x6,0x0};
uint8_t check[8] = {0x0,0x1,0x3,0x16,0x1c,0x8,0x0};
uint8_t cross[8] = {0x0,0x1b,0xe,0x4,0xe,0x1b,0x0};
uint8_t retarrow[8] = { 0x1,0x1,0x5,0x9,0x1f,0x8,0x4};
LiquidCrystal_I2C lcd(I2C_ADDR,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin,D7_pin);
void setup()
{
lcd.begin (20,4); // initialize the lcd
// Switch on the backlight
lcd.setBacklightPin(BACKLIGHT_PIN,POSITIVE);
lcd.setBacklight(LED_ON);
lcd.createChar(0, bell);
lcd.createChar(1, note);
lcd.createChar(2, clock);
lcd.createChar(3, heart);
lcd.createChar(4, duck);
lcd.createChar(5, check);
lcd.createChar(6, cross);
lcd.createChar(7, retarrow);
lcd.home();
lcd.setCursor(0, 0);
for(int i = 0;i < 20; i++) lcd.printByte(6);
lcd.setCursor(0, 1);
lcd.printByte(6);
lcd.print(" Hello world ");
lcd.printByte(6);
lcd.setCursor(0, 2);
lcd.printByte(6);
lcd.print(" i ");
lcd.printByte(3);
lcd.print(" arduinos! ");
lcd.printByte(6);
lcd.setCursor(0, 3);
for(int i = 0;i < 20; i++) lcd.printByte(6);
// lcd.clear();
}
void loop()
{
}
I have attached DFRobot's I2C adapter board schematic to this post.
DFRobot may have been the original board designer given their more professional approach of decent documentation, but given China's disregard for intellectual property rights, who knows for sure? Also, DFRobot has and active forum with timely responses by their engineers, and a wiki, which is another plus for their professionalism. DFRobot's board and SainSmart's significantly differ, physically, so if SainSmart copied DFRobot, it was only from their schematic and not the board design.
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