AN720 データシートの表示（PDF） - Silicon Laboratories

部品番号

コンポーネント説明

メーカー

AN720

PRECISION32 OPTIMIZATIONCONSIDERATIONS FOR CODESIZE ANDSPEED

Silicon Laboratories 

AN720

6.4. Function Library Usage

The removal of debugging printf() statements can dramatically reduce the code size of a project. A simple way to

do this is to redefine the printf function at the top of the file containing the printf() calls using the following

statement:

#define printf(args...)

For si32Library examples such as demo_si32UsbAudio, define the statement at the top of myBuildOptions.h to

remove all calls to printf(). Additionally, reduce the footprint by disabling logging in myBuildOptions.h:

#define si32BuildOption_enable_logging 0

This method preserves the printf() statements for later use, if needed. The printf() define can also be

encapsulated with preprocessor #if statements to automatically include this define when building with a Release

configuration.

To verify that all instances of printf() have been removed, search the map file for the project for the printf library. In

the sim3u1xx_Blinky example, this means adding the statement to both the main.c and gCpu.c files.

Using the sim3u1xx_Blinky and demo_si32UsbAudio default examples in the si32HAL 1.0.1 software package,

Table 19 and Table 20 show the relative build sizes with the different printf() settings. This section does not include

the CoreMark tests since printf is not part of the CoreMark benchmark.

Table 19. Keil printf() Comparison—sim3u1xx_Blinky Debug

Library

µVision MicroLIB with printf

µVision MicroLIB without printf

Code (bytes)

2068

1392

Read Only Data Read-Write Data

(bytes)

(bytes)

296

24

296

12

Zero-Initialized

Data (bytes)

1536

1536

Table 20. Keil printf() Comparison—demo_si32UsbAudio Debug

Library

µVision MicroLIB with printf

µVision MicroLIB without printf

Code (bytes)

47264

39760

Read Only Data Read-Write Data

(bytes)

(bytes)

3832

5208

4312

5196

Zero-Initialized

Data (bytes)

17972

17972

Rev. 0.1

21

Share Link: