drivers: auxdisplay: hd44780: rework the initialization procedure

If proper power supply is used to power the hd44780, it initializes
correctly on a reset condition all by itself. However,
if the power supply is below its expectations (e.g. some 3.3V Nucleo
board), it won't initialize properly on its own, and the MCU
has to carry out the initialization as listed in the reference manual.
Since we cannot determine it properly in the runtime,
always carry out the initialization procedure.

Signed-off-by: Jan Kuliga <[email protected]>

Author: kuliga

drivers/auxdisplay/auxdisplay_hd44780.c

@@ -77,6 +77,7 @@ struct auxdisplay_hd44780_config {
 
 static void auxdisplay_hd44780_set_entry_mode(const struct device *dev);
 static void auxdisplay_hd44780_set_display_mode(const struct device *dev, bool enabled);
+static int auxdisplay_hd44780_clear(const struct device *dev);
 
 static void hd44780_pulse_enable_line(const struct device *dev)
 {
@@ -109,13 +110,53 @@ static void auxdisplay_hd44780_command(const struct device *dev, bool rs, uint8_
 	}
 }
 
+static void hd44780_ic_initialize(const struct device *dev)
+{
+	const struct auxdisplay_hd44780_config *config = dev->config;
+	uint8_t cmd;
+
+	/*
+	 * If proper power supply is used to power the HD44780, it initializes correctly
+	 * on a reset condition all by itself. However, if the power supply is below
+	 * its expectations (e.g. supplying it with some 3.3V Nucleo board),
+	 * it won't initialize properly on its own, and the MCU has to carry out
+	 * the initialization as listed in the reference manual.
+	 * Since we cannot determine it properly in the runtime,
+	 * always carry out the initialization procedure.
+	 */
+	cmd = AUXDISPLAY_HD44780_CMD_SETUP | AUXDISPLAY_HD44780_8_BIT_CONFIG;
+	auxdisplay_hd44780_command(dev, false, cmd, AUXDISPLAY_HD44780_MODE_4_BIT_ONCE);
+	k_sleep(K_USEC(4100));
+	auxdisplay_hd44780_command(dev, false, cmd, AUXDISPLAY_HD44780_MODE_4_BIT_ONCE);
+	k_sleep(K_USEC(100));
+	auxdisplay_hd44780_command(dev, false, cmd, AUXDISPLAY_HD44780_MODE_4_BIT_ONCE);
+	k_sleep(K_USEC(100));
+
+	if (config->capabilities.mode == AUXDISPLAY_HD44780_MODE_4_BIT) {
+		/* Put display into 4-bit mode */
+		cmd = AUXDISPLAY_HD44780_CMD_SETUP;
+		auxdisplay_hd44780_command(dev, false, cmd, AUXDISPLAY_HD44780_MODE_4_BIT_ONCE);
+	}
+
+	/* Configure display */
+	if (config->capabilities.rows > 1) {
+		cmd |= AUXDISPLAY_HD44780_2_LINE_CONFIG;
+	}
+	auxdisplay_hd44780_command(dev, false, cmd, config->capabilities.mode);
+
+	auxdisplay_hd44780_set_display_mode(dev, false);
+	auxdisplay_hd44780_clear(dev);
+	auxdisplay_hd44780_set_entry_mode(dev);
+
+	auxdisplay_hd44780_set_display_mode(dev, true);
+}
+
 static int auxdisplay_hd44780_init(const struct device *dev)
 {
 	const struct auxdisplay_hd44780_config *config = dev->config;
 	struct auxdisplay_hd44780_data *data = dev->data;
 	int rc;
 	uint8_t i = 0;
-	uint8_t cmd = AUXDISPLAY_HD44780_CMD_SETUP | AUXDISPLAY_HD44780_8_BIT_CONFIG;
 
 	if (config->capabilities.mode > AUXDISPLAY_HD44780_MODE_8_BIT) {
 		/* This index is reserved for internal driver usage */
@@ -199,28 +240,7 @@ static int auxdisplay_hd44780_init(const struct device *dev)
 		k_sleep(K_MSEC(config->boot_delay));
 	}
 
-	if (config->capabilities.mode == AUXDISPLAY_HD44780_MODE_4_BIT) {
-		/* Reset display to known state in 8-bit mode */
-		auxdisplay_hd44780_command(dev, false, cmd, AUXDISPLAY_HD44780_MODE_4_BIT_ONCE);
-		auxdisplay_hd44780_command(dev, false, cmd, AUXDISPLAY_HD44780_MODE_4_BIT_ONCE);
-
-		/* Put display into 4-bit mode */
-		cmd = AUXDISPLAY_HD44780_CMD_SETUP;
-		auxdisplay_hd44780_command(dev, false, cmd, AUXDISPLAY_HD44780_MODE_4_BIT_ONCE);
-	}
-
-	if (config->capabilities.rows > 1) {
-		cmd |= AUXDISPLAY_HD44780_2_LINE_CONFIG;
-	}
-
-	/* Configure display */
-	auxdisplay_hd44780_command(dev, false, cmd, config->capabilities.mode);
-	auxdisplay_hd44780_set_display_mode(dev, true);
-	auxdisplay_hd44780_set_entry_mode(dev);
-	auxdisplay_hd44780_command(dev, false, AUXDISPLAY_HD44780_CMD_CLEAR,
-				   config->capabilities.mode);
-
-	k_sleep(K_USEC(config->clear_delay));
+	hd44780_ic_initialize(dev);
 
 	return 0;
 }