.. note:: Hello, welcome to the SunFounder Raspberry Pi & Arduino & ESP32 Enthusiasts Community on Facebook! Dive deeper into Raspberry Pi, Arduino, and ESP32 with fellow enthusiasts. **Why Join?** - **Expert Support**: Solve post-sale issues and technical challenges with help from our community and team. - **Learn & Share**: Exchange tips and tutorials to enhance your skills. - **Exclusive Previews**: Get early access to new product announcements and sneak peeks. - **Special Discounts**: Enjoy exclusive discounts on our newest products. - **Festive Promotions and Giveaways**: Take part in giveaways and holiday promotions. 👉 Ready to explore and create with us? Click [|link_sf_facebook|] and join today! .. _py_i2c_lcd1602: 2.17 Show Characters on I2 LCD1602 ============================================ LCD1602 is a character type liquid crystal display, which can display 32 (16*2) characters at the same time. As we all know, though LCD and some other displays greatly enrich the man-machine interaction, they share a common weakness. When they are connected to a controller, multiple IOs will be occupied of the controller which has no so many outer ports. Also it restricts other functions of the controller. Therefore, LCD1602 with an I2C bus is developed to solve the problem. * `Inter-Integrated Circuit - Wikipedia `_ I2C(Inter-Integrated Circuit) bus is a very popular and powerful bus for communication between a master device (or master devices) and a single or multiple slave devices. I2C main controller can be used to control IO expander, various sensors, EEPROM, ADC/DAC and so on. All of these are controlled only by the two pins of host, the serial data (SDA) line and the serial clock line(SCL). These two pins must be connected to specific pins of the microcontroller. There are two pairs of I2C communication interfaces in Pico, which are marked as I2C0 and I2C1, as shown in the figure below. .. image:: img/pin_pic2.png Here we will use the I2C0 interface to control the LCD1602 and display text. Schematic ----------- .. image:: img/Lcd1602.png :width: 600 Wiring ---------------------------- .. image:: img/wiring_lcd.png 1. Connect VCC of LCD to VBUS of Pico. #. Connect the GND of LCD to the GND of Pico. #. Connect SDA of LCD to GP0 of Pico, which is I2C0 SDA. #. Connect SCL of LCD to GP1 of Pico, which is I2C0 SCL. .. _py_create_library: Create a Library ---------------------- The following is the library of lcd1602 packaged by SunFounder. You need to create a new file, copy the following code into it and save it to Raspberry Pi Pico under the name ``lcd1602.py``. You can then call it inside of other programs. .. code-block:: python import machine import time class LCD(): def __init__(self, addr=0x27, blen=1): sda = machine.Pin(0) scl = machine.Pin(1) self.bus = machine.I2C(0,sda=sda, scl=scl, freq=400000) #print(self.bus.scan()) self.addr = addr self.blen = blen self.send_command(0x33) # Must initialize to 8-line mode at first time.sleep(0.005) self.send_command(0x32) # Then initialize to 4-line mode time.sleep(0.005) self.send_command(0x28) # 2 Lines & 5*7 dots time.sleep(0.005) self.send_command(0x0C) # Enable display without cursor time.sleep(0.005) self.send_command(0x01) # Clear Screen self.bus.writeto(self.addr, bytearray([0x08])) def write_word(self, data): temp = data if self.blen == 1: temp |= 0x08 else: temp &= 0xF7 self.bus.writeto(self.addr, bytearray([temp])) def send_command(self, cmd): # Send bit7-4 firstly buf = cmd & 0xF0 buf |= 0x04 # RS = 0, RW = 0, EN = 1 self.write_word(buf) time.sleep(0.002) buf &= 0xFB # Make EN = 0 self.write_word(buf) # Send bit3-0 secondly buf = (cmd & 0x0F) << 4 buf |= 0x04 # RS = 0, RW = 0, EN = 1 self.write_word(buf) time.sleep(0.002) buf &= 0xFB # Make EN = 0 self.write_word(buf) def send_data(self, data): # Send bit7-4 firstly buf = data & 0xF0 buf |= 0x05 # RS = 1, RW = 0, EN = 1 self.write_word(buf) time.sleep(0.002) buf &= 0xFB # Make EN = 0 self.write_word(buf) # Send bit3-0 secondly buf = (data & 0x0F) << 4 buf |= 0x05 # RS = 1, RW = 0, EN = 1 self.write_word(buf) time.sleep(0.002) buf &= 0xFB # Make EN = 0 self.write_word(buf) def clear(self): self.send_command(0x01) # Clear Screen def openlight(self): # Enable the backlight self.bus.writeto(self.addr,bytearray([0x08])) # self.bus.close() def write(self, x, y, str): if x < 0: x = 0 if x > 15: x = 15 if y < 0: y = 0 if y > 1: y = 1 # Move cursor addr = 0x80 + 0x40 * y + x self.send_command(addr) for chr in str: self.send_data(ord(chr)) def message(self, text): #print("message: %s"%text) for char in text: if char == '\n': self.send_command(0xC0) # next line else: self.send_data(ord(char)) Code ------------- Then, create a new file, and call the lcd1602 library stored before in this file. .. code-block:: python from lcd1602 import LCD import utime lcd = LCD() string = " Hello!\n" lcd.message(string) utime.sleep(2) string = " Sunfounder!" lcd.message(string) utime.sleep(2) lcd.clear() After the program runs, you will be able to see two lines of text appear on the LCD in turn, and then disappear. How it works? -------------------------- In the lcd1602 library, we integrate the relevant functions of lcd1602 into the LCD class. Import lcd1602 library .. code-block:: python from lcd1602 import LCD Declare an object of the LCD class and name it lcd. .. code-block:: python lcd = LCD() This statement will display the text on the LCD. It should be noted that the argument must be a string type. If we want to pass an integer or float, we must use the forced conversion statement ``str()``. .. code-block:: python lcd.message(string) If you call this statement multiple times, lcd will superimpose the texts. This requires the use of the following statement to clear the display. .. code-block:: python lcd.clear() What more? -------------------------- We can combine thermistor and I2C LCD1602 to make a room temperature meter. .. image:: img/wiring_lcd_2.png .. code-block:: python from lcd1602 import LCD import machine import utime import math thermistor = machine.ADC(28) lcd = LCD() while True: temperature_value = thermistor.read_u16() Vr = 3.3 * float(temperature_value) / 65535 Rt = 10000 * Vr / (3.3 - Vr) temp = 1/(((math.log(Rt / 10000)) / 3950) + (1 / (273.15+25))) Cel = temp - 273.15 #Fah = Cel * 1.8 + 32 #print ('Celsius: %.2f C Fahrenheit: %.2f F' % (Cel, Fah)) #utime.sleep_ms(200) string = " Temperature is \n " + str('{:.2f}'.format(Cel))+ " C" lcd.message(string) utime.sleep(1) lcd.clear()