--- /dev/null
+/*
+ * ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42):
+ * <joerg@FreeBSD.ORG> wrote this file. As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return. Joerg Wunsch
+ * ----------------------------------------------------------------------------
+ *
+ * HD44780 LCD display driver
+ *
+ * The LCD controller is used in 4-bit mode with a full bi-directional
+ * interface (i.e. R/~W is connected) so the busy flag can be read.
+ *
+ * $Id: hd44780.c 2002 2009-06-25 20:21:16Z joerg_wunsch $
+ */
+
+#include "avr_hd44780_conf.h"
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <avr/io.h>
+#include <util/delay.h>
+
+#include "avr_hd44780.h"
+
+#define GLUE(a, b) a##b
+
+/* single-bit macros, used for control bits */
+#define SET_(what, p, m) GLUE(what, p) |= (1 << (m))
+#define CLR_(what, p, m) GLUE(what, p) &= ~(1 << (m))
+#define GET_(/* PIN, */ p, m) GLUE(PIN, p) & (1 << (m))
+#define SET(what, x) SET_(what, x)
+#define CLR(what, x) CLR_(what, x)
+#define GET(/* PIN, */ x) GET_(x)
+
+/* nibble macros, used for data path */
+#define ASSIGN_(what, p, m, v) GLUE(what, p) = (GLUE(what, p) & \
+ ~((1 << (m)) | (1 << ((m) + 1)) | \
+ (1 << ((m) + 2)) | (1 << ((m) + 3)))) | \
+ ((v) << (m))
+#define READ_(what, p, m) (GLUE(what, p) & ((1 << (m)) | (1 << ((m) + 1)) | \
+ (1 << ((m) + 2)) | (1 << ((m) + 3)))) >> (m)
+#define ASSIGN(what, x, v) ASSIGN_(what, x, v)
+#define READ(what, x) READ_(what, x)
+
+#define HD44780_BUSYFLAG 0x80
+
+/*
+ * Send one pulse to the E signal (enable). Mind the timing
+ * constraints. If readback is set to true, read the HD44780 data
+ * pins right before the falling edge of E, and return that value.
+ */
+static inline uint8_t
+hd44780_pulse_e(bool readback) __attribute__((always_inline));
+
+static inline uint8_t
+hd44780_pulse_e(bool readback)
+{
+ uint8_t x;
+
+ SET(PORT, HD44780_E);
+ /*
+ * Guarantee at least 500 ns of pulse width. For high CPU
+ * frequencies, a delay loop is used. For lower frequencies, NOPs
+ * are used, and at or below 1 MHz, the native pulse width will
+ * already be 1 us or more so no additional delays are needed.
+ */
+#if F_CPU > 4000000UL
+ _delay_us(0.5);
+#else
+ /*
+ * When reading back, we need one additional NOP, as the value read
+ * back from the input pin is sampled close to the beginning of a
+ * CPU clock cycle, while the previous edge on the output pin is
+ * generated towards the end of a CPU clock cycle.
+ */
+ if (readback)
+ __asm__ volatile("nop");
+# if F_CPU > 1000000UL
+ __asm__ volatile("nop");
+# if F_CPU > 2000000UL
+ __asm__ volatile("nop");
+ __asm__ volatile("nop");
+# endif /* F_CPU > 2000000UL */
+# endif /* F_CPU > 1000000UL */
+#endif
+ if (readback)
+ x = READ(PIN, HD44780_D4);
+ else
+ x = 0;
+ CLR(PORT, HD44780_E);
+
+ return x;
+}
+
+/*
+ * Send one nibble out to the LCD controller.
+ */
+static void
+hd44780_outnibble(uint8_t n, uint8_t rs)
+{
+ CLR(PORT, HD44780_RW);
+ if (rs)
+ SET(PORT, HD44780_RS);
+ else
+ CLR(PORT, HD44780_RS);
+ ASSIGN(PORT, HD44780_D4, n);
+ (void)hd44780_pulse_e(false);
+}
+
+/*
+ * Send one byte to the LCD controller. As we are in 4-bit mode, we
+ * have to send two nibbles.
+ */
+void
+hd44780_outbyte(uint8_t b, uint8_t rs)
+{
+ hd44780_outnibble(b >> 4, rs);
+ hd44780_outnibble(b & 0xf, rs);
+}
+
+/*
+ * Read one nibble from the LCD controller.
+ */
+static uint8_t
+hd44780_innibble(uint8_t rs)
+{
+ uint8_t x;
+
+ SET(PORT, HD44780_RW);
+ ASSIGN(DDR, HD44780_D4, 0x00);
+ if (rs)
+ SET(PORT, HD44780_RS);
+ else
+ CLR(PORT, HD44780_RS);
+ x = hd44780_pulse_e(true);
+ ASSIGN(DDR, HD44780_D4, 0x0F);
+ CLR(PORT, HD44780_RW);
+
+ return x;
+}
+
+/*
+ * Read one byte (i.e. two nibbles) from the LCD controller.
+ */
+uint8_t
+hd44780_inbyte(uint8_t rs)
+{
+ uint8_t x;
+
+ x = hd44780_innibble(rs) << 4;
+ x |= hd44780_innibble(rs);
+
+ return x;
+}
+
+/*
+ * Wait until the busy flag is cleared.
+ */
+void
+hd44780_wait_ready(bool longwait)
+{
+#if USE_BUSY_BIT
+ while (hd44780_incmd() & HD44780_BUSYFLAG) ;
+#else
+ if (longwait)
+ _delay_ms(1.52);
+ else
+ _delay_us(37);
+#endif
+}
+
+/*
+ * Initialize the LCD controller.
+ *
+ * The initialization sequence has a mandatory timing so the
+ * controller can safely recognize the type of interface desired.
+ * This is the only area where timed waits are really needed as
+ * the busy flag cannot be probed initially.
+ */
+void
+hd44780_init(void)
+{
+ SET(DDR, HD44780_RS);
+ SET(DDR, HD44780_RW);
+ SET(DDR, HD44780_E);
+ ASSIGN(DDR, HD44780_D4, 0x0F);
+
+ _delay_ms(15); /* 40 ms needed for Vcc = 2.7 V */
+ hd44780_outnibble(HD44780_FNSET(1, 0, 0) >> 4, 0);
+ _delay_ms(4.1);
+ hd44780_outnibble(HD44780_FNSET(1, 0, 0) >> 4, 0);
+ _delay_ms(0.1);
+ hd44780_outnibble(HD44780_FNSET(1, 0, 0) >> 4, 0);
+ _delay_us(40); /* 37 is too short */
+
+ hd44780_outnibble(HD44780_FNSET(0, 1, 0) >> 4, 0);
+ hd44780_wait_ready(false);
+ hd44780_outcmd(HD44780_FNSET(0, 1, 0));
+ hd44780_wait_ready(false);
+ hd44780_outcmd(HD44780_DISPCTL(0, 0, 0));
+ hd44780_wait_ready(false);
+}
+
+/*
+ * Prepare the LCD controller pins for powerdown.
+ */
+void
+hd44780_powerdown(void)
+{
+ ASSIGN(PORT, HD44780_D4, 0);
+ CLR(PORT, HD44780_RS);
+ CLR(PORT, HD44780_RW);
+ CLR(PORT, HD44780_E);
+}
projects / simavr / blobdiff