Update/solution:
The sample program(s) Gordon refers to are at github/wiringPi - specifically for me lcd-adafruit.c. On my Rpi, the correct libraries are in /usr/lib and are libwiringPi.so and libwiringPiDev.so.
from /home/pi/bin this works:
gcc -o lcd-adafruit lcd-adafruit.c -lwiringPi -lwiringPiDev
I must assume both libraries are in the buster distro - I previously installed Adafruit package(s) to use the I2C LCD display in Python3 on this Rpi.
Thanks - keep well.
Update:
I discovered Gordon's forum with posts dated 2012 - 2013. He offers some sample programs with wiringPi functions and some suggested compile/link commands - for example:
gcc -o filename.c -I/usr/local/include filename -L/usr/local/lib -lwiringPi
Lots of tries, lots of missing file errors - as well, on this buster rpi3, the library path does not include /local. Running each step separately, the preprocessor, the compiler, and the assembler finish without errors, but the linker stops on missing symbols in different library modules. Seems like maybe a shared library issue - any ideas?
Dirk: Thanks for cleaning up the look of my question and the code.
Joan: gcc i2clcd.c -o i2clcd executed command from /home/pi
I have become aware that Gordon has moved on/wiringpi is deprecated, but the last update to gpio was 2018 - seems pretty current to me .... enlighten me as needed. Also, both of the included wiringPi header files are found in /usr/include, and the relevant setup function appears in each. Thanks.
Raspbian buster on Rpi3 with Adafruit 16 x 2 LCD display on I2C. Display works fine with Python3 test program. Gordon's example gpio commands also work. gpio version is 2.50.
I am moving a working Arduino C++ application with the LCD display to Rpi. Neither (WiringPi) Gordon's sample programs or the sample .c program from bristolwatch.com will compile - both sources #include and . Compile fails with undefined reference to wiringPiSetup() and wiringPiI2CSetup(). The compiler does not report any missing libraries.
The gpio package is the package that comes with buster - when I tried an install with apt-get, Apt-get reported I had the latest version. Many other forum questions here indicate that wiringpi should be working, but most other questions are a bit older. What am I missing here? I am attaching Lewis Loftin's (bristolwatch) sample code that does not compile for me.`
/*
*
* by Lewis Loflin www.bristolwatch.com lewis@bvu.net
* http://www.bristolwatch.com/rpi/i2clcd.htm
* Using wiringPi by Gordon Henderson
*
*
* Port over lcd_i2c.py to C and added improvements.
* Supports 16x2 and 20x4 screens.
* This was to learn now the I2C lcd displays operate.
* There is no warrenty of any kind use at your own risk.
*
*/
#include <wiringPiI2C.h>
#include <wiringPi.h>
#include <stdlib.h>
#include <stdio.h>
// Define some device parameters
#define I2C_ADDR 0x27 // I2C device address
// Define some device constants
#define LCD_CHR 1 // Mode - Sending data
#define LCD_CMD 0 // Mode - Sending command
#define LINE1 0x80 // 1st line
#define LINE2 0xC0 // 2nd line
#define LCD_BACKLIGHT 0x08 // On
// LCD_BACKLIGHT = 0x00 # Off
#define ENABLE 0b00000100 // Enable bit
void lcd_init(void);
void lcd_byte(int bits, int mode);
void lcd_toggle_enable(int bits);
// added by Lewis
void typeInt(int i);
void typeFloat(float myFloat);
void lcdLoc(int line); //move cursor
void ClrLcd(void); // clr LCD return home
void typeln(const char *s);
void typeChar(char val);
int fd; // seen by all subroutines
int main() {
if (wiringPiSetup () == -1) exit (1);
fd = wiringPiI2CSetup(I2C_ADDR);
//printf("fd = %d ", fd);
lcd_init(); // setup LCD
char array1[] = "Hello world!";
while (1) {
lcdLoc(LINE1);
typeln("Using wiringPi");
lcdLoc(LINE2);
typeln("Geany editor.");
delay(2000);
ClrLcd();
lcdLoc(LINE1);
typeln("I2c Programmed");
lcdLoc(LINE2);
typeln("in C not Python.");
delay(2000);
ClrLcd();
lcdLoc(LINE1);
typeln("Arduino like");
lcdLoc(LINE2);
typeln("fast and easy.");
delay(2000);
ClrLcd();
lcdLoc(LINE1);
typeln(array1);
delay(2000);
ClrLcd(); // defaults LINE1
typeln("Int ");
int value = 20125;
typeInt(value);
delay(2000);
lcdLoc(LINE2);
typeln("Float ");
float FloatVal = 10045.25989;
typeFloat(FloatVal);
delay(2000);
}
return 0;
}
// float to string
void typeFloat(float myFloat) {
char buffer[20];
sprintf(buffer, "%4.2f", myFloat);
typeln(buffer);
}
// int to string
void typeInt(int i) {
char array1[20];
sprintf(array1, "%d", i);
typeln(array1);
}
// clr lcd go home loc 0x80
void ClrLcd(void) {
lcd_byte(0x01, LCD_CMD);
lcd_byte(0x02, LCD_CMD);
}
// go to location on LCD
void lcdLoc(int line) {
lcd_byte(line, LCD_CMD);
}
// out char to LCD at current position
void typeChar(char val) {
lcd_byte(val, LCD_CHR);
}
// this allows use of any size string
void typeln(const char *s) {
while ( *s ) lcd_byte(*(s++), LCD_CHR);
}
void lcd_byte(int bits, int mode) {
//Send byte to data pins
// bits = the data
// mode = 1 for data, 0 for command
int bits_high;
int bits_low;
// uses the two half byte writes to LCD
bits_high = mode | (bits & 0xF0) | LCD_BACKLIGHT ;
bits_low = mode | ((bits << 4) & 0xF0) | LCD_BACKLIGHT ;
// High bits
wiringPiI2CReadReg8(fd, bits_high);
lcd_toggle_enable(bits_high);
// Low bits
wiringPiI2CReadReg8(fd, bits_low);
lcd_toggle_enable(bits_low);
}
void lcd_toggle_enable(int bits) {
// Toggle enable pin on LCD display
delayMicroseconds(500);
wiringPiI2CReadReg8(fd, (bits | ENABLE));
delayMicroseconds(500);
wiringPiI2CReadReg8(fd, (bits & ~ENABLE));
delayMicroseconds(500);
}
void lcd_init() {
// Initialise display
lcd_byte(0x33, LCD_CMD); // Initialise
lcd_byte(0x32, LCD_CMD); // Initialise
lcd_byte(0x06, LCD_CMD); // Cursor move direction
lcd_byte(0x0C, LCD_CMD); // 0x0F On, Blink Off
lcd_byte(0x28, LCD_CMD); // Data length, number of lines, font size
lcd_byte(0x01, LCD_CMD); // Clear display
delayMicroseconds(500);
}`
