Initial Release

i2c/lcd_1602_i2c/CMakeLists.txt

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+add_executable(lcd_1602_i2c
+        lcd_1602_i2c.c
+        )
+
+# Pull in our (to be renamed) simple get you started dependencies
+target_link_libraries(lcd_1602_i2c pico_stdlib hardware_i2c)
+
+# create map/bin/hex file etc.
+pico_add_extra_outputs(lcd_1602_i2c)
+
+# add url via pico_set_program_url
+example_auto_set_url(lcd_1602_i2c)

i2c/lcd_1602_i2c/README.adoc

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+= Attaching a 16x2 LCD via I2C
+
+This example code shows how to interface the Raspberry Pi Pico to one of the very common 16x2 LCD character displays. The display will need a 3.3V I2C adapter board as this example uses I2C for communications.
+
+[NOTE]
+======
+These LCD displays can also be driven directly using GPIO without the use of an adapter board. That is beyond the scope of this example.
+======
+
+== Wiring information
+
+Wiring up the device requires 4 jumpers, to connect VCC (3.3v), GND, SDA and SCL. The example here uses I2C port 0, which is assigned to GPIO 4 (SDA) and 5 (SCL) in software. Power is supplied from the 3.3V pin.
+
+WARNING: Many displays of this type are 5v. If you wish to use a 5v display you will need to use level shifters on the SDA and SCL lines to convert from the 3.3V used by the RP2040. Whilst a 5v display will just about work at 3.3v, the display will be dim.
+
+
+[[lcd_1602_i2c_wiring]]
+[pdfwidth=75%]
+.Wiring Diagram for LCD1602A LCD with I2C bridge.
+image::lcd_1602_i2c_bb.png[]
+
+== List of Files
+
+CMakeLists.txt:: CMake file to incorporate the example in to the examples build tree.
+lcd_1602_i2c.c:: The example code.
+
+== Bill of Materials
+
+.A list of materials required for the example
+[[lcd_1602_i2c-bom-table]]
+[cols=3]
+|===
+| *Item* | *Quantity* | Details
+| Breadboard | 1 | generic part
+| Raspberry Pi Pico | 1 | http://raspberrypi.org/
+| 1602A based LCD panel 3.3v | 1 | generic part
+| 1602A to I2C bridge device 3.3v | 1 | generic part
+| M/M Jumper wires | 4 | generic part
+|===
+
+

i2c/lcd_1602_i2c/lcd_1602_i2c.c

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+/**
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include "pico/stdlib.h"
+#include "hardware/i2c.h"
+#include "pico/binary_info.h"
+
+/* Example code to drive a 16x2 LCD panel via a I2C bridge chip (e.g. PCF8574)
+
+   NOTE: The panel must be capable of being driven at 3.3v NOT 5v. The Pico
+   GPIO (and therefor I2C) cannot be used at 5v.
+
+   You will need to use a level shifter on the I2C lines if you want to run the
+   board at 5v.
+
+   Connections on Raspberry Pi Pico board, other boards may vary.
+
+   GPIO 4 (pin 6)-> SDA on LCD bridge board
+   GPIO 5 (pin 7)-> SCL on LCD bridge board
+   3.3v (pin 36) -> VCC on LCD bridge board
+   GND (pin 38)  -> GND on LCD bridge board
+*/
+// commands
+const int LCD_CLEARDISPLAY = 0x01;
+const int LCD_RETURNHOME = 0x02;
+const int LCD_ENTRYMODESET = 0x04;
+const int LCD_DISPLAYCONTROL = 0x08;
+const int LCD_CURSORSHIFT = 0x10;
+const int LCD_FUNCTIONSET = 0x20;
+const int LCD_SETCGRAMADDR = 0x40;
+const int LCD_SETDDRAMADDR = 0x80;
+
+// flags for display entry mode
+const int LCD_ENTRYSHIFTINCREMENT = 0x01;
+const int LCD_ENTRYLEFT = 0x02;
+
+// flags for display and cursor control
+const int LCD_BLINKON = 0x01;
+const int LCD_CURSORON = 0x02;
+const int LCD_DISPLAYON = 0x04;
+
+// flags for display and cursor shift
+const int LCD_MOVERIGHT = 0x04;
+const int LCD_DISPLAYMOVE = 0x08;
+
+// flags for function set
+const int LCD_5x10DOTS = 0x04;
+const int LCD_2LINE = 0x08;
+const int LCD_8BITMODE = 0x10;
+
+// flag for backlight control
+const int LCD_BACKLIGHT = 0x08;
+
+const int LCD_ENABLE_BIT = 0x04;
+
+#define I2C_PORT i2c0
+// By default these LCD display drivers are on bus address 0x27
+static int addr = 0x27;
+
+// Modes for lcd_send_byte
+#define LCD_CHARACTER  1
+#define LCD_COMMAND    0
+
+#define MAX_LINES      2
+#define MAX_CHARS      16
+
+/* Quick helper function for single byte transfers */
+void i2c_write_byte(uint8_t val) {
+    i2c_write_blocking(I2C_PORT, addr, &val, 1, false);
+}
+
+void lcd_toggle_enable(uint8_t val) {
+    // Toggle enable pin on LCD display
+    // We cannot do this too quickly or things don't work
+#define DELAY_US 600
+    sleep_us(DELAY_US);
+    i2c_write_byte(val | LCD_ENABLE_BIT);
+    sleep_us(DELAY_US);
+    i2c_write_byte(val & ~LCD_ENABLE_BIT);
+    sleep_us(DELAY_US);
+}
+
+// The display is sent a byte as two separate nibble transfers
+void lcd_send_byte(uint8_t val, int mode) {
+    uint8_t high = mode | (val & 0xF0) | LCD_BACKLIGHT;
+    uint8_t low = mode | ((val << 4) & 0xF0) | LCD_BACKLIGHT;
+
+    i2c_write_byte(high);
+    lcd_toggle_enable(high);
+    i2c_write_byte(low);
+    lcd_toggle_enable(low);
+}
+
+void lcd_clear(void) {
+    lcd_send_byte(LCD_CLEARDISPLAY, LCD_COMMAND);
+}
+
+// go to location on LCD
+void lcd_set_cursor(int line, int position) {
+    int val = (line == 0) ? 0x80 + position : 0xC0 + position;
+    lcd_send_byte(val, LCD_COMMAND);
+}
+
+static void inline lcd_char(char val) {
+    lcd_send_byte(val, LCD_CHARACTER);
+}
+
+void lcd_string(const char *s) {
+    while (*s) {
+        lcd_char(*s++);
+    }
+}
+
+void lcd_init() {
+    lcd_send_byte(0x03, LCD_COMMAND);
+    lcd_send_byte(0x03, LCD_COMMAND);
+    lcd_send_byte(0x03, LCD_COMMAND);
+    lcd_send_byte(0x02, LCD_COMMAND);
+
+    lcd_send_byte(LCD_ENTRYMODESET | LCD_ENTRYLEFT, LCD_COMMAND);
+    lcd_send_byte(LCD_FUNCTIONSET | LCD_2LINE, LCD_COMMAND);
+    lcd_send_byte(LCD_DISPLAYCONTROL | LCD_DISPLAYON, LCD_COMMAND);
+    lcd_clear();
+}
+
+int main() {
+    // This example will use I2C0 on GPIO4 (SDA) and GPIO5 (SCL)
+    i2c_init(I2C_PORT, 100 * 1000);
+    gpio_set_function(4, GPIO_FUNC_I2C);
+    gpio_set_function(5, GPIO_FUNC_I2C);
+    gpio_pull_up(4);
+    gpio_pull_up(5);
+    // Make the I2C pins available to picotool
+    bi_decl( bi_2pins_with_func(4, 5, GPIO_FUNC_I2C));
+
+    lcd_init();
+
+    static uint8_t *message[] =
+            {
+                    "RP2040 by", "Raspberry Pi",
+                    "A brand new", "microcontroller",
+                    "Twin core M0", "Full C SDK",
+                    "More power in", "your product",
+                    "More beans", "than Heinz!"
+            };
+
+    while (1) {
+        for (int m = 0; m < sizeof(message) / sizeof(message[0]); m += MAX_LINES) {
+            for (int line = 0; line < MAX_LINES; line++) {
+                lcd_set_cursor(line, (MAX_CHARS / 2) - strlen(message[m + line]) / 2);
+                lcd_string(message[m + line]);
+            }
+            sleep_ms(2000);
+            lcd_clear();
+        }
+    }
+
+    return 0;
+}