1. Baremetal C Programming for Embedded Systems
Class 5: Writing Portable Code
February 27, 2015 Jacob Beningo, CSDP

2. Course Overview C Concepts for Embedded Systems
Baremetal Scheduling Techniques
Driver Design Techniques
Design Patterns for Firmware
Writing Portable Code

3. Session Overview
Why Write Portable Code?
API Design
An EEPROM Example

4. Benefits of Portable Code
Easily moved from one MCU to the next
Proven and tested
Decreases development time
Decreases costs
Familiarity which makes maintenance easier

5. Hardware Abstraction Layer

6. API’s Application Programming Interfaces
Critical to creating reusable software
Defines a common interface that can be used from one project to the next
Identifies useful peripheral features
If adhered to at a driver level application code can be reused and ported with ease
Example API’s and Standards
Linux Kernel
AUTOSAR
Arduino Libraries
Custom
etc

7. API’s
Digital Input / Output (Gpio)
Serial Peripheral Interface
EEPROM

8. EEPROM Overview

9. EEPROM Configuration
Header Definitions

10. EEPROM Configuration
Source Definitions

11. EEPROM Driver
Header Definitions

12. EEPROM Driver
Initialization

13. EEPROM Driver
Write Status Register

14. EEPROM Driver
Read Status Register

15. Portable Code Tips Avoid the use of #pragma
Keep modules as de-coupled as possible
One “function” per module
Create an API
Keep configuration separate from implementation
Use only standard C concepts (bit field ex.)
Encapsulation and data hiding

16. Course Review Use of static and volatile A Review of C Concepts
Scheduling Techniques
Methods of Accessing Memory
Circular Buffers
Driver Design
GPIO, SPI, External EEPROM

17. Additional Resources Download Course Material for
Updated C Doxygen Templates (Feb 2015)
Example drivers source code
Microcontroller API Standard
EDN Embedded Basics Articles
Embedded Bytes Newsletter
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