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wiringPi/examples: improve i2c-lcd.c

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Signed-off-by: Steve Jeong <how2soft@gmail.com>
Change-Id: I8602dca171b3d681d5481b541e087bed47d2a761
This commit is contained in:
Steve Jeong
2023-06-02 11:43:29 +09:00
parent 0bdc5a78e4
commit 18668e8b6c
1 changed files with 12 additions and 19 deletions
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31
examples/i2c-lcd.c
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@@ -28,7 +28,6 @@
// Define some device parameters // Define some device parameters
#define I2C_ADDR 0x3f // I2C device address #define I2C_ADDR 0x3f // I2C device address
#define LCD_WIDTH 20
// Define some device constants // Define some device constants
#define LCD_CHR 1 // Mode - Sending data #define LCD_CHR 1 // Mode - Sending data
@@ -40,7 +39,7 @@
#define LINE4 0xD4 // 4th line #define LINE4 0xD4 // 4th line
#define LCD_BACKLIGHT 0x08 // On #define LCD_BACKLIGHT 0x08 // On
// LCD_BACKLIGHT = 0x00 # Off // #define LCD_BACKLIGHT 0x00 // Off
#define ENABLE 0b00000100 // Enable bit #define ENABLE 0b00000100 // Enable bit
@@ -50,15 +49,12 @@ void lcd_toggle_enable(int bits);
void display_string(const char *string, int line); void display_string(const char *string, int line);
int fd; int fd;
char *bus; /* /dev/i2c-0 ~ /dev/i2c-9 */ char *bus = "0"; /* /dev/i2c-0 ~ /dev/i2c-9 */
int address; int address = 0x3f;
int main(int argc, char *argv[]) { int main(int argc, char *argv[]) {
char device[16] = "/dev/i2c-"; char device[12];
bus = "0";
address = 0x3f;
if (wiringPiSetup () == -1) if (wiringPiSetup () == -1)
exit (1); exit (1);
@@ -71,30 +67,27 @@ int main(int argc, char *argv[]) {
address = strtoul(argv[2], NULL, 16); address = strtoul(argv[2], NULL, 16);
} }
strncat(device, bus, 1); snprintf(device, 11, "%s%s", "/dev/i2c-", bus);
fd = wiringPiI2CSetupInterface(device, address); fd = wiringPiI2CSetupInterface(device, address);
lcd_init(); // setup LCD lcd_init(); // setup LCD
while (1) { while (1) {
display_string("Hard Kernel", LINE1); display_string("HardKernel", LINE1);
display_string("Hello ODROID", LINE2); display_string("Hello ODROID", LINE2);
} }
return 0; return 0;
} }
void display_string(const char *string, int line) { void display_string(const char *string, int line) {
// go to location on LCD // go to location on LCD
lcd_byte(line, LCD_CMD); lcd_byte(line, LCD_CMD);
if (strlen(string) > LCD_WIDTH) { while (*string) {
printf("message is too long!\n"); lcd_byte(*(string++), LCD_CHR);
return;
} }
while (*string) lcd_byte(*(string++), LCD_CHR);
} }
void lcd_byte(int bits, int mode) { void lcd_byte(int bits, int mode) {
@@ -105,8 +98,8 @@ void lcd_byte(int bits, int mode) {
int bits_high; int bits_high;
int bits_low; int bits_low;
// uses the two half byte writes to LCD // uses the two half byte writes to LCD
bits_high = mode | (bits & 0xf0) | LCD_BACKLIGHT ; bits_high = mode | (bits & 0xf0) | LCD_BACKLIGHT;
bits_low = mode | ((bits << 4) & 0xf0) | LCD_BACKLIGHT ; bits_low = mode | ((bits << 4) & 0xf0) | LCD_BACKLIGHT;
// High bits // High bits
wiringPiI2CReadReg8(fd, bits_high); wiringPiI2CReadReg8(fd, bits_high);
@@ -117,7 +110,7 @@ void lcd_byte(int bits, int mode) {
lcd_toggle_enable(bits_low); lcd_toggle_enable(bits_low);
} }
void lcd_toggle_enable(int bits) { void lcd_toggle_enable(int bits) {
// Toggle enable pin on LCD display // Toggle enable pin on LCD display
delayMicroseconds(500); delayMicroseconds(500);
wiringPiI2CReadReg8(fd, (bits | ENABLE)); wiringPiI2CReadReg8(fd, (bits | ENABLE));
@@ -126,7 +119,7 @@ void lcd_toggle_enable(int bits) {
delayMicroseconds(500); delayMicroseconds(500);
} }
void lcd_init() { void lcd_init() {
// Initialise display // Initialise display
lcd_byte(0x33, LCD_CMD); // Initialise lcd_byte(0x33, LCD_CMD); // Initialise
lcd_byte(0x32, LCD_CMD); // Initialise lcd_byte(0x32, LCD_CMD); // Initialise