August 2019 AN3307 Rev 6 1/38

AN3307

Application note

Guidelines for obtaining IEC 60335

Class B certification for any STM32 application

Introduction

The role of safety has become very important for electronics applications. The level of safety

requirements for components used in electronic designs is steadily increasing. The

manufacturers of electronic devices include many new technical solutions in the design of

new components. Software techniques for improving safety are continuously being

developed.

The current safety recommendations and requirements are specified at worldwide level by

recognized international standards bodies such as IEC (International electrotechnical

commission) and come under the compliance, verification and certification process of

testing houses and authorities like VDE (Association for electrical, electronic and

information technologies). The certification process is closely associated with the

Electromagnetic compatibility (EMC) tests when the robustness of the system against the

noise emission and the noise sensitivity is tested for the compliance with international

standards.

The main purpose of this application note and its associated software

(a)

(STM32-CLASSB-SPL) is to facilitate and accelerate the user software development and

the certification processes for appliances which are subject to these requirements and

certifications and are based on some of the ST 32-bit family of microcontrollers.

There are three packages certified by VDE for the 32-bit ST microcontrollers covering the

STM32F0, STM32F1 and STM32F3 Series microcontrollers, referred to in this document as

STM32F. All the certified packages are based on dedicated CMSIS and standard peripheral

libraries (SPL) and all of them use similar principles described by this document, with focus

on the main differences. While using the hardware and firmware compatibility between ST

families, these packages can also be adapted for some other ST 32-bit microcontrollers not

certified for SPL (for example STM32F2, STM32F4 or STM32L1 Series)

(b)

a. All the Class B firmware packages are available upon request only, contact the nearest ST sales office.

b. STMicroelectronics is developing derivative firmware supporting new products step by step. Contact the local

ST sales office to obtain the latest information about available packages and plans for their certification.

www.st.com

Contents AN3307

2/38 AN3307 Rev 6

Contents

1 Package variation overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2 Main differences between STM32F packages

and their possible modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Compliance with IEC and VDE standards . . . . . . . . . . . . . . . . . . . . . . . 11

3.1 Generic tests included in the STM32F firmware library . . . . . . . . . . . . . . 12

3.2 Application-specific tests not included in the ST firmware library . . . . . . . 14

4 Class B software package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.1 Basic software principles used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.1.1 Fail Safe mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.1.2 Class B variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.1.3 Class B flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.2 Package organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.2.1 Projects included in the package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.2.2 Tool-specific integration of the library . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.2.3 Application demonstration example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.3 Package configuration and debugging . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.3.1 Configuration control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.3.2 Verbose diagnostic mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.3.3 Debugging the package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

5 Class B solution structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

5.1 Integrating the software into the user application . . . . . . . . . . . . . . . . . . . 22

5.2 Description of startup self tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

5.2.1 CPU startup self-test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5.2.2 Watchdog startup self-test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

5.2.3 Flash complete checksum self-test . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.2.4 Full RAM March C-/X self-test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.2.5 Clock startup self-test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

5.3 Periodic runtime self-test initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

5.4 Description of periodic runtime self-tests . . . . . . . . . . . . . . . . . . . . . . . . . 31

5.4.1 Runtime self-test structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31