Introduction

The NUCLEO-8S208RB (built around the STM8S208RBT6 device) and the NUCLEO-8L152R8 (built around the

STM8L152R8T6 device) are boards that allow the evaluation of the main features of all the STM8S Series and STM8L Series

microcontrollers.

This application note provides a short description on how to use the GPIOs and the interrupt controllers on the

NUCLEO-8S208RB and on the NUCLEO-8L152R8 to drive a set of LEDs.

Once the microcontroller (STM8S208RBT6 or STM8L152R8T6 in this example) has been powered-up through a USB cable

connected to the host PC, the LD2 and LD5 LEDs (not on-board LEDs) start blinking. Each time that the "push" button is

pressed, the interrupt controller assets an interrupt that is used to control the I/Os, and changes the LED behavior.

Table 1. Applicable products

Type Part number

Evaluation boards

NUCLEO-8S208RB

NUCLEO-8L152R8

Reference documents

• STM8 Nucleo-64 boards data brief (DB3591)

• STM8L152R8T6 Nucleo-64 board user manual (UM2351)

• STM8S208RBT6 Nucleo-64 board user manual (UM2364)

Using the GPIOs and interrupt controller to drive LEDs on STM8 Nucleo-64

boards

AN5178

Application note

AN5178 - Rev 1 - June 2018

For further information contact your local STMicroelectronics sales office.

www.st.com

1 Application description

This section describes the hardward requirements, the application's schematics and the application's principle to

use the GPIOs and the interrupt controller to drive a set of LEDs on the NUCLEO-8S208RB or the

NUCLEO-8L152R8 boards.

1.1 Hardware requirements

No on-board resources are required other than the user push-button.

The external components required by the application are listed on the table below.

Table 2. External hardware components required

External components Value Comments

LD2, LD3, LD4, LD5 - Standards LEDs

R2, R3, R4, R5 510 Ω Protective resistors

1.2 Application schematics

The figure below shows how to interface the LEDs and the push button with the NUCLEO-8S208RB or the

NUCLEO-8L152R8 boards. For details on NUCLEO-8S208RB or NUCLEO-8L152R8 boards implementation,

refer to the board schematics provided in the corresponding user manual (UM2351 or UM2364).

Protective resistors, R2, R3, R4, and R5, are mandatory to limit the current to a value that does not harm the

LEDs. The push button requires a debounce filter (RC) and a pull-up resistor (R1) to avoid triggering several

interrupts due to the mechanical bouncing of the button.

Figure 1. STM8S Series application schematic

R5 R4 R3 R2

LD5 LD4 LD3 LD2

PB2

STM8S208RBT6

PB3 PB4 PB5

PE4

User’s push button

AN5178

Application description

AN5178 - Rev 1

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