raspberry pi lcd module 20x4 pricelist

Adding a display to Raspberry PI Pico allows getting real time information from connected devices without using a computer from USB port. I2C LCD displays (with PCF8574 backpack) are one of best solution to keep wiring simple

I2C LCD displays are common LCD displays, usually composed of 16 columns x 2 rows blocks, but also different configurations can be found. Differently from simple LCD displays, they include a small panel soldered in its backside, including chips able to reduce their connection wires. The I2C LCD display usually has a PCF8574 chip, which is a device able to convert I2C serial communication into parallel connections.

To connect an I2C LCD Display with your Raspberry PI Pico, you just need to wire the Vcc and GND PINs from display to VSYS and a GND PINs of RPI Pico, then SDA and SCL PINs from the I2C Display to a couple of SDA and SCL PINs from Raspberry PI Pico, belonging to the same I2C bus, as shown in the picture on the following wiring diagram chapter.

A working solution uses the dhylands-python_lcd module including a generic API to interface to LCD displays. But this class implements commands to be sent to the LCD without caring about how to send them. The reason is that there are many different backpacks and every solution can be implemented in many different ways. The ones created with a PCF8574 use I2C as communication protocol, in this case, you need a sort of driver able to send commands via I2C. This function is implemented with a second module from T-622 user, also available from T-622 GitHub page.

As usual, I suggest adding from now to your favourite e-commerce shopping cart all the needed hardware, so that at the end you will be able to evaluate overall costs and decide if continue with the project or remove them from the shopping cart. So, hardware will be only:

Prepare cabling according to the previous paragraph. Connect RPI Pico to Thonny (you can refer to my tutorial about First steps with Raspberry PI Pico).

Before going into the usage explanation, you have to be sure that your LCD’s I2C address is correct. This is a unique address shared between I2C devices to make them able to talk on the same shared wire. This is usually a hexadecimal value and all devices connected to your RPI Pico can be scanned by copy-paste of the following code in your Thonny shell (you can copy all lines together):

As I2C LCD with PCF8574 backpack use PCF8574 chip for I2C communication, you will probably get its default address (0x27). But if your project includes more PCF8574-based chips, then you will need to identify the LCD one between those that will be shown. In case of missing devices, please check your cabling.

Starting to use your LCD device, you can run a generic test with the T-622 test script, which I have pre-configured for 16×2 LCDs using I2C0 channel (ports GP0 and GP1 according to my wiring diagram). This modified script can be get from my download area (use the following link: i2c_lcd_test). Save this file in your Raspberry PI Pico root folder or in your computer and open it with Thonny IDE.

If you will see nothing, please check your cabling. Another common issue with I2C LCD display is getting a clean screen which is only powering on and off. This means that your connection is correct and everything is working, you have only to adjust your LCD contrast by rotating the screw positioned in your LCD backside, which controls a potentiometer managing contrast:

The LCD API used has a flexible feature allowing users to display also complex icons inside a single cell. Some special characters are already available and depend on your LCD ROM (Read Only Memory, space not visible to the user). You can use these chars with “lcd.putchar(chr())” function.

The first 8 characters (from 0 to 7) character-generator RAM. This means that you can define and design any icon you want to display by identifying pixels to be put on/off for each char block, made of 8 rows and 5 columns of pixels. Each row A good description of how to define a generic icon is explained in https://github.com/dhylands/python_lcd.

You can use the generated code with “lcd.custom_char()” command. An example usage is built in my pico_i2c_lcd script. Download and open it in your Thonny IDE.

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