If an I2C error occurs when sending a nibble, continue to try and send the second nibble to reduce the chance of the display getting out of sync. Refactor init() function into init() and reset(), to allow users to reset the display without reinitialising with the smbus instance or backlight.

Author: DavidAntliff

i2c-lcd1602.c

@@ -201,45 +201,35 @@ static esp_err_t _write_to_expander(const i2c_lcd1602_info_t * i2c_lcd1602_info,
     return smbus_send_byte(i2c_lcd1602_info->smbus_info, data | i2c_lcd1602_info->backlight_flag);
 }
 
+// IMPORTANT - for the display to stay "in sync" it is important that errors do not interrupt the
+// 2 x nibble sequence.
+
 // clock data from expander to LCD by causing a falling edge on Enable
 static esp_err_t _strobe_enable(const i2c_lcd1602_info_t * i2c_lcd1602_info, uint8_t data)
 {
-    esp_err_t err = _write_to_expander(i2c_lcd1602_info, data | FLAG_ENABLE);
-    if (err == ESP_OK)
-    {
-        ets_delay_us(DELAY_ENABLE_PULSE_WIDTH);
-        err = _write_to_expander(i2c_lcd1602_info, data & ~FLAG_ENABLE);
-        if (err == ESP_OK)
-        {
-            ets_delay_us(DELAY_ENABLE_PULSE_SETTLE);
-            ESP_LOGD(TAG, "enable strobed");
-        }
-    }
-    return err;
+    esp_err_t err1 = _write_to_expander(i2c_lcd1602_info, data | FLAG_ENABLE);
+    ets_delay_us(DELAY_ENABLE_PULSE_WIDTH);
+    esp_err_t err2 = _write_to_expander(i2c_lcd1602_info, data & ~FLAG_ENABLE);
+    ets_delay_us(DELAY_ENABLE_PULSE_SETTLE);
+    return err1 ? err1 : err2;
 }
 
 // send top nibble to the LCD controller
 static esp_err_t _write_top_nibble(const i2c_lcd1602_info_t * i2c_lcd1602_info, uint8_t data)
 {
     ESP_LOGD(TAG, "_write_top_nibble 0x%02x", data);
-    esp_err_t err = _write_to_expander(i2c_lcd1602_info, data);
-    if (err == ESP_OK)
-    {
-        err = _strobe_enable(i2c_lcd1602_info, data);
-    }
-    return err;
+    esp_err_t err1 = _write_to_expander(i2c_lcd1602_info, data);
+    esp_err_t err2 = _strobe_enable(i2c_lcd1602_info, data);
+    return err1 ? err1 : err2;
 }
 
 // send command or data to controller
 static esp_err_t _write(const i2c_lcd1602_info_t * i2c_lcd1602_info, uint8_t value, uint8_t register_select_flag)
 {
     ESP_LOGD(TAG, "_write 0x%02x | 0x%02x", value, register_select_flag);
-    esp_err_t err = _write_top_nibble(i2c_lcd1602_info, (value & 0xf0) | register_select_flag);
-    if (err == ESP_OK)
-    {
-        err = _write_top_nibble(i2c_lcd1602_info, ((value & 0x0f) << 4) | register_select_flag);
-    }
-    return err;
+    esp_err_t err1 = _write_top_nibble(i2c_lcd1602_info, (value & 0xf0) | register_select_flag);
+    esp_err_t err2 = _write_top_nibble(i2c_lcd1602_info, ((value & 0x0f) << 4) | register_select_flag);
+    return err1 ? err1 : err2;
 }
 
 // send command to controller
@@ -309,51 +299,7 @@ esp_err_t i2c_lcd1602_init(i2c_lcd1602_info_t * i2c_lcd1602_info, smbus_info_t *
         // Wait at least 40ms after power rises above 2.7V before sending commands.
         ets_delay_us(DELAY_POWER_ON);
 
-        // put Expander into known state - Register Select and Read/Write both low
-        err = _write_to_expander(i2c_lcd1602_info, 0);
-        if (err == ESP_OK)
-        {
-            ets_delay_us(1000);
-
-            // select 4-bit mode on LCD controller - see datasheet page 46, figure 24.
-            err = _write_top_nibble(i2c_lcd1602_info, 0x03 << 4);
-            if (err == ESP_OK)
-            {
-                ets_delay_us(DELAY_INIT_1);
-                err = _write_top_nibble(i2c_lcd1602_info, 0x03 << 4);  // repeat
-                if (err == ESP_OK)
-                {
-                    ets_delay_us(DELAY_INIT_2);
-                    err = _write_top_nibble(i2c_lcd1602_info, 0x03 << 4);  // repeat
-                    if (err == ESP_OK)
-                    {
-                        ets_delay_us(DELAY_INIT_3);
-                        err = _write_top_nibble(i2c_lcd1602_info, 0x02 << 4);  // select 4-bit mode
-                        if (err == ESP_OK)
-                        {
-                            // now we can use the command()/write() functions
-                            err = _write_command(i2c_lcd1602_info, COMMAND_FUNCTION_SET | FLAG_FUNCTION_SET_MODE_4BIT | FLAG_FUNCTION_SET_LINES_2 | FLAG_FUNCTION_SET_DOTS_5X8);
-                            if (err == ESP_OK)
-                            {
-                                err = _write_command(i2c_lcd1602_info, COMMAND_DISPLAY_CONTROL | i2c_lcd1602_info->display_control_flags);
-                                if (err == ESP_OK)
-                                {
-                                    err = i2c_lcd1602_clear(i2c_lcd1602_info);
-                                    if (err == ESP_OK)
-                                    {
-                                        err = _write_command(i2c_lcd1602_info, COMMAND_ENTRY_MODE_SET | i2c_lcd1602_info->entry_mode_flags);
-                                        if (err == ESP_OK)
-                                        {
-                                            err = i2c_lcd1602_home(i2c_lcd1602_info);
-                                        }
-                                    }
-                                }
-                            }
-                        }
-                    }
-                }
-            }
-        }
+        err = i2c_lcd1602_reset(i2c_lcd1602_info);
     }
     else
     {
@@ -363,6 +309,98 @@ esp_err_t i2c_lcd1602_init(i2c_lcd1602_info_t * i2c_lcd1602_info, smbus_info_t *
     return err;
 }
 
+esp_err_t i2c_lcd1602_reset(const i2c_lcd1602_info_t * i2c_lcd1602_info)
+{
+    esp_err_t first_err = ESP_OK;
+    esp_err_t last_err = ESP_FAIL;
+
+    // put Expander into known state - Register Select and Read/Write both low
+    if ((last_err = _write_to_expander(i2c_lcd1602_info, 0)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: _write_to_expander 1 failed: %d", last_err);
+    }
+
+    ets_delay_us(1000);
+
+    // select 4-bit mode on LCD controller - see datasheet page 46, figure 24.
+    if ((last_err = _write_top_nibble(i2c_lcd1602_info, 0x03 << 4)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: _write_top_nibble 1 failed: %d", last_err);
+    }
+
+    ets_delay_us(DELAY_INIT_1);
+
+    // repeat
+    if ((last_err = _write_top_nibble(i2c_lcd1602_info, 0x03 << 4)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: _write_top_nibble 2 failed: %d", last_err);
+    }
+
+    ets_delay_us(DELAY_INIT_2);
+
+    // repeat
+    if ((last_err = _write_top_nibble(i2c_lcd1602_info, 0x03 << 4)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: _write_top_nibble 3 failed: %d", last_err);
+    }
+
+    ets_delay_us(DELAY_INIT_3);
+
+    // select 4-bit mode
+    if ((last_err = _write_top_nibble(i2c_lcd1602_info, 0x02 << 4)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: _write_top_nibble 4 failed: %d", last_err);
+    }
+
+    // now we can use the command()/write() functions
+    if ((last_err = _write_command(i2c_lcd1602_info, COMMAND_FUNCTION_SET | FLAG_FUNCTION_SET_MODE_4BIT | FLAG_FUNCTION_SET_LINES_2 | FLAG_FUNCTION_SET_DOTS_5X8)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: _write_command 1 failed: %d", last_err);
+    }
+
+    if ((last_err = _write_command(i2c_lcd1602_info, COMMAND_DISPLAY_CONTROL | i2c_lcd1602_info->display_control_flags)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: _write_command 2 failed: %d", last_err);
+    }
+
+    if ((last_err = i2c_lcd1602_clear(i2c_lcd1602_info)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: i2c_lcd1602_clear failed: %d", last_err);
+    }
+
+    if ((last_err = _write_command(i2c_lcd1602_info, COMMAND_ENTRY_MODE_SET | i2c_lcd1602_info->entry_mode_flags)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: _write_command 3 failed: %d", last_err);
+    }
+
+    if ((last_err = i2c_lcd1602_home(i2c_lcd1602_info)) != ESP_OK)
+    {
+        if (first_err == ESP_OK)
+            first_err = last_err;
+        ESP_LOGE(TAG, "reset: i2c_lcd1602_home failed: %d", last_err);
+    }
+
+    return first_err;
+}
+
 esp_err_t i2c_lcd1602_clear(const i2c_lcd1602_info_t * i2c_lcd1602_info)
 {
     esp_err_t err = ESP_FAIL;

include/i2c-lcd1602.h

@@ -127,9 +127,18 @@ void i2c_lcd1602_free(i2c_lcd1602_info_t ** tsl2561_info);
  *
  * @param[in] i2c_lcd1602_info Pointer to I2C-LCD1602 info instance.
  * @param[in] smbus_info Pointer to SMBus info instance.
+ * @return ESP_OK if successful, otherwise an error constant.
  */
 esp_err_t i2c_lcd1602_init(i2c_lcd1602_info_t * i2c_lcd1602_info, smbus_info_t * smbus_info, bool backlight);
 
+/**
+ * @brief Reset the display. Custom characters will be cleared.
+ *
+ * @param[in] i2c_lcd1602_info Pointer to I2C-LCD1602 info instance.
+ * @return ESP_OK if successful, otherwise an error constant.
+ */
+esp_err_t i2c_lcd1602_reset(const i2c_lcd1602_info_t * i2c_lcd1602_info);
+
 /**
  * @brief Clears entire display (clears DDRAM) and returns cursor to home position.
  *        DDRAM content is cleared, CGRAM content is not changed.