LCD 16x2 HD44780 Tutorial 4 - Character Entry Mode

In this tutorial, I will discuss about character entry mode of LCD 16x2 HD44780. There are 4 character entry mode that can be selected. So far, we have been used the default character entry mode until previous post. The entry mode is auto-incrementing the cursor address every new character is entered. It is also possible to auto-decrementing the cursor and combine with shifting the display.

This is the first entry mode or the default entry mode. To do this we can send instruction 0b00000110 to the LCD. This is the default entry mode every LCD powered on. Every new character is entered, the cursor/ DDRAM address is auto-incremented by 1. This mode is illustrated by picture below:

1. Set cursor to 0x07 address location.
2. Put char 'A' on 0x07 location, cursor auto-incremented to 0x08 address location.
3. Put char 'B' on 0x08 location, cursor auto-incremented to 0x09 address location.
4. Put char 'C' on 0x09 location, cursor auto-incremented to 0x0A address location.
5. Return home (0x00 location).

LCD 16x2 HD44780 Tutorial 3 - Display Address and Shifting

In previous tutorial, we have done displaying a word "AnNyeongHaSeYo!" (Hello in Korean) on LCD 16x2. In this tutorial, I will explain about addressing to DDRAM (Display Data RAM). The function of DDRAM is to store character that displayed on LCD screen. 

HD44780 LCD controller has 128 different addresses for DDRAM, although not all addresses have their own location on LCD screen. Only 80 display locations can be used to store characters. HD44780 is a LCD controller that can be used not just for 16x2 LCD size, but also for other size such as 16x4, 20x2, or 40x2. The display location for all LCD size is also same (80 location). The different is number of location that can displayed on screen. For example, on 16x2 size is only 32 location, but other location still can be used to store character, although not displayed. To displayed that, we can shift the display right or left. This is the address location of DDRAM that displayed on LCD 16x2 size every LCD power on:

STM32F4 Discovery Tutorial 10 - PWM

In this tutorial, I will share how to use PWM on STM32F4 Discovery board. PWM (Pulse Width Modulation) is a technique for generating analog voltage (average value) by using microcontroller's digital outputs. PWM is used in DC motor speed control, servo motor control, dimming LED, audio generation and many more.

PWM signal is a modulated digital logic (0 and 1). PWM signal have a duty cycle. Duty cycle is measured in percentage. The percentage of duty cycle is calculated from time of a digital signal is on over period of time.

STM32F4 Discovery Tutorial 9 - Timer Interrupt

In this tutorial, I will share how to generate interrupt every given interval using timer on STM32F4 Discovery board. For example project, we will make orange LED toggle every 500ms interval using TIM2. In the main program we will toggle blue LED every 2500ms (blue LED toggling will not using timer interrupt, but just use delay function).

First, we write code for initialize timer. We will use TIM2. This is the block diagram for configuring the timer clock:

void TIM_INT_Init()
{
    // Enable clock for TIM2
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

    // TIM2 initialization overflow every 500ms
    // TIM2 by default has clock of 84MHz
    // Here, we must set value of prescaler and period,
    // so update event is 0.5Hz or 500ms
    // Update Event (Hz) = timer_clock / ((TIM_Prescaler + 1) * 
    // (TIM_Period + 1))
    // Update Event (Hz) = 84MHz / ((4199 + 1) * (9999 + 1)) = 2 Hz
    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
    TIM_TimeBaseInitStruct.TIM_Prescaler = 4199;
    TIM_TimeBaseInitStruct.TIM_Period = 9999;
    TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Up;

    // TIM2 initialize
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseInitStruct);
    // Enable TIM2 interrupt
    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);
    // Start TIM2
    TIM_Cmd(TIM2, ENABLE);

    // Nested vectored interrupt settings
    // TIM2 interrupt is most important (PreemptionPriority and 
    // SubPriority = 0)
    NVIC_InitTypeDef NVIC_InitStruct;
    NVIC_InitStruct.NVIC_IRQChannel = TIM2_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);
}

STM32F4 Discovery Tutorial 8 - External Interrupt

In this tutorial, I will share how to use external interrupt on STM32F4 Discovery. STM32F4 has 23 external interrupt. These external interrupt lines is consist of 2 sections. First sections (line0 to line15) is for external interrupt from GPIO pins (P0 to P15). The other section is for peripherals events (RTC, Ethernet, USB).

We can use 16 external interrupt line (line0 to line15) to detect external event from GPIO pins. Each pin from all GPIO port is connected to each external interrupt line with the same number.

• PA0, PB0, PC0 and so on, are multiplexed to line0. So you can only configure one of these pins to connect to line0 interrupt.
• PA0 and PA8 are multiplexed to different line. So you can configure these pins to use external interrupt at the same time. Because PA0 is connected to line0 and PA8 is connected to line8.

STM32F4 Discovery Tutorial 7 - ADC

In this tutorial, I will share how to use ADC on STM32F4 Discovery to read analog voltage. ADC is stands for Analog to Digital Converter. Microcontrollers are digital component, so they only understand discrete/digital signals. Therefore if you want to read analog voltage that can be from various sensors, you need an ADC. STM32F407 has 3 ADC that can work independently. Every ADC have 18 channels. 16 channels are external and connected to GPIO pin. 2 channels are internal that connected to internal temperature sensor and ADC voltage reference.

When you use ADC, you can choose which ADC and its channel from this table: