We are going to summarise them in order to achieve our goal which is design a flexible library. #define LINE_D7 PAL_LINE(GPIOC, 7U) How it worksĪll the information about HD44780 working principle are extracted by the documentation previously introduce.

* Data PIN are connected from PC0 to PC7 */ Taking a look to the following code we can see how they are connected in our demo. It is possible to select which GPIOs are used through software. To do this K is connected to GND and A to a GPIO.Īll the remaining PINs are connected to a GPIO. Our library allows software backlight management using a PWM or PAL (we suggest PWM tutorial as further reading). In our case we have decided to manage it through a PWM or through an output PIN. The backlight could be connected to 3.3V being normally on ( A to 3.3V and K to GND) or it could be connected to a potentiometer allowing the dimmer. The contrast regulator PIN ( V0) has been connected to a 20k potentiometer which is between 3.3V and GND. Our connections are VSS to GND and VDD to 5V. The first two PINs are required to power up the chip. In our case we have connected the LCD to an STM32 Nucleo-64. V0 or VE, contrast pad that should be connected to a potentiometer.We will discuss this solution in another article. There are also some kits equipped with a 8-bit I/O expander for I2C bus which simplify connections and code but are costly. This display usually comes with a monochromatic backlight and a 16 PIN header connector. In this article we are going to use a 16×2 LCD driven by HD44780. HD44780 datasheet Hardware PIN-map A 16×2 LCDII based on HD44780 with pinmap. This task requires a preliminary read of HD44780 datasheet. We want to provide a full library for HD44780 compatible with ChibiOS/HAL 3.0 ad a demo explaining gradually how software has been designed. A common smaller size is 16×2, and this size is readily available as surplus stock for makers and prototyping work. The most commonly manufactured larger configuration is 40×4 characters, which requires two individually addressable HD44780 controllers with expansion chips as a single HD44780 chip can only address up to 80 characters. Larger custom sizes are made with 32, 40 and 80 characters and with 1, 2, 4 or 8 lines. Common sizes are one row of eight characters (1×8), as well as 16×2, 20×2 and 20×4 formats.

It is often used in industrial test equipment, networking equipment, vending machine and in embedded projects.Ĭompatible LCD screens are manufactured in several standard configurations. This controller is a standard de-facto for this kind of display. The HD44780 is a controller for display developed by Hitachi commonly used to manage alphanumeric dot matrix LCD.

Hd44780 lcd pinout