diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..401433f
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+*.o
+rpi4b-temp-humidity
\ No newline at end of file
diff --git a/Makefile b/Makefile
index 22fc18a..fc4bfac 100644
--- a/Makefile
+++ b/Makefile
@@ -2,15 +2,20 @@ CC=clang
 CFLAGS=-std=c99
 LD=clang
 LDFLAGS=-lgpio
-OBJS=main.o lcd.o
+OBJS=main.o util.o lcd.o
+OUTFILE=rpi4b-temp-humidity
+
+${OUTFILE}: ${OBJS}
+	${LD} ${LDFLAGS} -o $@ ${OBJS}
 
 main.o lcd.o: lcd.h
-
-rpi4b-temp-himidity: ${OBJS}
-	${LD} ${LDFLAGS} -o $@ ${OBJS}
+main.o util.o lcd.o: util.h
 
 .c.o:
 	${CC} ${CFLAGS} -c $<
 
+clean:
+	rm -f ${OUTFILE} ${OBJS}
+
 .SUFFIXES: .c .o
 .PHONY: clean
diff --git a/lcd.c b/lcd.c
new file mode 100644
index 0000000..599a133
--- /dev/null
+++ b/lcd.c
@@ -0,0 +1,140 @@
+/*
+ * lcd.c - Subroutines for communicating with HD44780U based LCD panels
+ * Copyright (C) 2024  Alexander Rosenberg
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version. See the LICENSE file for more information.
+ *
+ * This file was created with help from the document located here:
+ * https://www.sparkfun.com/datasheets/LCD/HD44780.pdf
+ */
+#include "lcd.h"
+#include "util.h"
+
+#include <unistd.h>
+
+static void lcd_set_read(LCD *lcd, bool is_read, bool force) {
+    if (force || lcd->is_read != is_read) {
+        gpio_config_t cfg = {.g_flags = is_read ? GPIO_PIN_INPUT
+                                        : GPIO_PIN_OUTPUT};
+        cfg.g_pin = lcd->d0;
+        gpio_pin_set_flags(lcd->handle, &cfg);
+        cfg.g_pin = lcd->d1;
+        gpio_pin_set_flags(lcd->handle, &cfg);
+        cfg.g_pin = lcd->d2;
+        gpio_pin_set_flags(lcd->handle, &cfg);
+        cfg.g_pin = lcd->d3;
+        gpio_pin_set_flags(lcd->handle, &cfg);
+        cfg.g_pin = lcd->d4;
+        gpio_pin_set_flags(lcd->handle, &cfg);
+        cfg.g_pin = lcd->d5;
+        gpio_pin_set_flags(lcd->handle, &cfg);
+        cfg.g_pin = lcd->d6;
+        gpio_pin_set_flags(lcd->handle, &cfg);
+        cfg.g_pin = lcd->d7;
+        gpio_pin_set_flags(lcd->handle, &cfg);
+        lcd->is_read = is_read;
+    }
+}
+
+static void lcd_pulse_enable(LCD *lcd) {
+    gpio_pin_high(lcd->handle, lcd->en);
+    usleep(1); // min of 1000ns
+    gpio_pin_low(lcd->handle, lcd->en);
+}
+
+LCD *lcd_open(gpio_handle_t handle, int rs, int rw, int en, int d0, int d1,
+              int d2, int d3, int d4, int d5, int d6, int d7) {
+    LCD *lcd = malloc_checked(sizeof(LCD));
+    lcd->handle = handle;
+    lcd->rs = rs;
+    lcd->rw = rw;
+    lcd->en = en;
+    lcd->d0 = d0;
+    lcd->d1 = d1;
+    lcd->d2 = d2;
+    lcd->d3 = d3;
+    lcd->d4 = d4;
+    lcd->d5 = d5;
+    lcd->d6 = d6;
+    lcd->d7 = d7;
+    lcd_set_read(lcd, false, true);
+    lcd_clear(lcd);
+    lcd_call(lcd, 0, 0, 0, 0, 1, 1, 1, 0, 0); // 5x8 font, 2 lines, 8bit
+    lcd_entry_mode(lcd, LCD_INCREMENT, LCD_CURSOR_MOVE);
+    lcd_display_control(lcd, LCD_CURSOR_NO_BLINK, LCD_CURSOR_OFF, LCD_DISPLAY_ON);
+    return lcd;
+}
+
+void lcd_close(LCD *lcd) {
+    free(lcd);
+}
+
+void lcd_call(LCD *lcd, int rs, int d0, int d1, int d2, int d3, int d4, int d5,
+              int d6, int d7) {
+    while(lcd_is_busy(lcd)) {
+        usleep(5);
+    }
+    lcd_set_read(lcd, false, false);
+    gpio_pin_low(lcd->handle, lcd->en);
+    gpio_pin_low(lcd->handle, lcd->rw);
+    gpio_pin_set(lcd->handle, lcd->rs, rs);
+    gpio_pin_set(lcd->handle, lcd->d0, d0);
+    gpio_pin_set(lcd->handle, lcd->d1, d1);
+    gpio_pin_set(lcd->handle, lcd->d2, d2);
+    gpio_pin_set(lcd->handle, lcd->d3, d3);
+    gpio_pin_set(lcd->handle, lcd->d4, d4);
+    gpio_pin_set(lcd->handle, lcd->d5, d5);
+    gpio_pin_set(lcd->handle, lcd->d6, d6);
+    gpio_pin_set(lcd->handle, lcd->d7, d7);
+    lcd_pulse_enable(lcd);
+}
+
+void lcd_write_char(LCD *lcd, char c) {
+    lcd_call(lcd, 1, c & 1, (c >> 1) & 1, (c >> 2) & 1, (c >> 3) & 1, (c >> 4) & 1,
+             (c >> 5) & 1, (c >> 6) & 1, (c >> 7) & 1);
+}
+
+size_t lcd_write_string(LCD *lcd, const char *str) {
+    size_t count;
+    for (count = 0; *str; ++str, ++count) {
+        lcd_write_char(lcd, *str);
+    }
+    return count;
+}
+
+void lcd_move_to(LCD *lcd, int line, int col) {
+    lcd_call(lcd, 0, col & 1, (col >> 1) & 1, (col >> 2) & 1,
+             (col >> 3) & 1, (col >> 4) & 1, (col >> 5) & 1, line, 1);
+}
+
+void lcd_clear(LCD *lcd) {
+    lcd_call(lcd, 0, 1, 0, 0, 0, 0, 0, 0, 0);
+}
+
+void lcd_display_control(LCD *lcd, int b, int c, int d) {
+    lcd_call(lcd, 0, b, c, d, 1, 0, 0, 0, 0);
+}
+
+void lcd_entry_mode(LCD *lcd, int id, int s) {
+    lcd_call(lcd, 0, s, id, 1, 0, 0, 0, 0, 0);
+}
+
+void lcd_cursor_shift(LCD *lcd, int sc, int rl) {
+    lcd_call(lcd, 0, 0, 0, rl, sc, 1, 0, 0, 0);
+}
+
+bool lcd_is_busy(LCD *lcd) {
+    lcd_set_read(lcd, true, false);
+    gpio_pin_low(lcd->handle, lcd->rs);
+    gpio_pin_high(lcd->handle, lcd->rw);
+    gpio_pin_high(lcd->handle, lcd->en);
+    usleep(1);
+    gpio_value_t busy = gpio_pin_get(lcd->handle, lcd->d7);
+    gpio_pin_low(lcd->handle, lcd->en);
+    usleep(1);
+    return busy;
+    
+}
diff --git a/lcd.h b/lcd.h
new file mode 100644
index 0000000..03fd977
--- /dev/null
+++ b/lcd.h
@@ -0,0 +1,107 @@
+/*
+ * lcd.h - Subroutines for communicating with HD44780U based LCD panels
+ * Copyright (C) 2024  Alexander Rosenberg
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version. See the LICENSE file for more information.
+ */
+#ifndef INCLUDED_LCD_H
+#define INCLUDED_LCD_H
+
+#include <sys/types.h>
+#include <libgpio.h>
+#include <stdbool.h>
+
+typedef struct {
+    gpio_handle_t handle;
+    // pin numbers
+    int rs; // register select
+    int rw; // read-write
+    int en; // enable
+    int d0;
+    int d1;
+    int d2;
+    int d3;
+    int d4;
+    int d5;
+    int d6;
+    int d7;
+
+    // internal use
+    bool is_read;
+} LCD;
+
+/*
+ * Allocate and initialize a new LCD object and return a pointer to it. HANDLE
+ * is a gpio_handle_t, each of the other arguments corresponds to the GPIO pin
+ * number that the given controller pin is connected to: "register select",
+ * "read-write", "enable", and data pins 0-7.
+ * Return: the newly created object.
+ */
+LCD *lcd_open(gpio_handle_t handle, int rs, int rw, int en, int d0, int d1,
+              int d2, int d3, int d4, int d5, int d6, int d7);
+/*
+ * Close LCD by freeing any resources associated with it.
+ */
+void lcd_close(LCD *lcd);
+/*
+ * Call a single instruction on LCD. Each argument is the value of that pin.
+ */
+void lcd_call(LCD *lcd, int rs, int d0, int d1, int d2, int d3, int d4, int d5,
+              int d6, int d7);
+/*
+ * Write character C to LCD.
+ */
+void lcd_write_char(LCD *lcd, char c);
+
+/*
+ * Write STR to LCD.
+ * Return: the number of characters written.
+ */
+size_t lcd_write_string(LCD *lcd, const char *str);
+
+/*
+ * Move the cursor to COL on LINE, which both start from 0.
+ */
+void lcd_move_to(LCD *lcd, int line, int col);
+
+/*
+ * Clear LCD and return the cursor to the top right.
+ */
+void lcd_clear(LCD *lcd);
+
+#define LCD_DISPLAY_ON 1
+#define LCD_DISPLAY_OFF 0
+#define LCD_CURSOR_ON 1
+#define LCD_CURSOR_OFF 0
+#define LCD_CURSOR_BLINK 1
+#define LCD_CURSOR_NO_BLINK 0
+/*
+ * Control B, cursor blink, C, cursor visibility, and D, display power for LCD.
+ */
+void lcd_display_control(LCD *lcd, int b, int c, int d);
+
+#define LCD_INCREMENT 1
+#define LCD_DECREMENT 0
+#define LCD_DISPLAY_SHIFT 1
+#define LCD_CURSOR_MOVE 0
+#define LCD_SHIFT_RIGHT 1
+#define LCD_SHIFT_LEFT 0
+/*
+ * Control shift and increment for LCD.
+ */
+void lcd_entry_mode(LCD *lcd, int id, int s);
+
+/*
+ * Control direction and shift/move for cursor for LCD.
+ */
+void lcd_cursor_shift(LCD *lcd, int sc, int rl);
+
+/*
+ * Return: weather the busy flag is set for LCD.
+ */
+bool lcd_is_busy(LCD *lcd);
+
+#endif
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..48791a7
--- /dev/null
+++ b/main.c
@@ -0,0 +1,30 @@
+#include "lcd.h"
+
+#include <unistd.h>
+#include <err.h>
+
+#define RS 2
+#define RW 3
+#define EN 4
+#define D0 17
+#define D1 27
+#define D2 22
+#define D3 10
+#define D4 9
+#define D5 14
+#define D6 15
+#define D7 18
+
+int main(int argc, const char **argv) {
+    gpio_handle_t handle = gpio_open(0);
+    if (handle == GPIO_INVALID_HANDLE) {
+        errx(1, "count not open GPIO handle!");
+    }
+    LCD *lcd = lcd_open(handle, RS, RW, EN, D0, D1, D2, D3, D4, D5, D6, D7);
+    lcd_write_string(lcd, "This is a test");
+    lcd_move_to(lcd, 1, 0);
+    lcd_write_string(lcd, "FreeBSD!");
+    lcd_close(lcd);
+    gpio_close(handle);
+    return 0;
+}
diff --git a/util.c b/util.c
new file mode 100644
index 0000000..8994062
--- /dev/null
+++ b/util.c
@@ -0,0 +1,29 @@
+/*
+ * util.c - Utility functions
+ * Copyright (C) 2024  Alexander Rosenberg
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version. See the LICENSE file for more information.
+ */
+#include "util.h"
+
+#include <err.h>
+
+struct GlobalFlags GLOBAL_FLAGS = {
+    .config_path = NULL,
+    .gpio_path = NULL,
+};
+
+void *malloc_checked(size_t n) {
+    return realloc_checked(NULL, n);
+}
+
+void *realloc_checked(void *old_ptr, size_t n) {
+    void *ptr = realloc(old_ptr, n);
+    if (n && !ptr) {
+        errx(1, "out of memory!");
+    }
+    return ptr;
+}
diff --git a/util.h b/util.h
new file mode 100644
index 0000000..d0989ba
--- /dev/null
+++ b/util.h
@@ -0,0 +1,33 @@
+/*
+ * util.h - Utility functions
+ * Copyright (C) 2024  Alexander Rosenberg
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later
+ * version. See the LICENSE file for more information.
+ */
+#ifndef INCLUDED_UTIL_H
+#define INCLUDED_UTIL_H
+
+#include <stdlib.h>
+
+struct GlobalFlags {
+    const char *config_path; // path to config file
+    const char *gpio_path; // path of GPIO device file to use
+};
+extern struct GlobalFlags GLOBAL_FLAGS;
+
+/*
+ * Like malloc(3), except that if allocation fails, an error will be written to
+ * standard error and abort(3) called
+ */
+void *malloc_checked(size_t n);
+
+/*
+ * Like realloc(3), except that if allocation fails, an error will be written to
+ * standard error and abort(3) called
+ */
+void *realloc_checked(void *old_ptr, size_t n);
+
+#endif