I tested running bare bones code using ESP IDF on an ESP32 chip using duinotech XC-3800, and obtained the following results in terms of image size.
Analysis Binary Size for ESP32
Folder Structure
- temp/
- main/
- CMakeLists.txt
- main.c
- CMakeLists.txt
- main/
File contents
CMakeLists.txt
# The following lines of boilerplate have to be in your project's
# CMakeLists in this exact order for cmake to work correctly
cmake_minimum_required(VERSION 3.5)
include($ENV{IDF_PATH}/tools/cmake/project.cmake)
project(temp)
main>CMakeLists.txt
idf_component_register(SRCS "main.c"
INCLUDE_DIRS "")
Test 1 main>main.c
#include <stdio.h>
void app_main(void) {
printf("Hello world!\n");
for (int i = 10; i >= 0; i--) {
printf("Restarting in %d seconds...\n", i);
}
printf("Restarting now.\n");
fflush(stdout);
}
Test 2 main>main.c
#include <stdio.h>
void app_main(void) { printf("Hello world!\n"); }
Test 3 main>main.c
void app_main(void) {}
Size comparison
Obtained by running idf_size.py build/temp.map
Test 1
Total sizes:
DRAM .data size: 8320 bytes
DRAM .bss size: 4072 bytes
Used static DRAM: 12392 bytes ( 168344 available, 6.9% used)
Used static IRAM: 38804 bytes ( 92268 available, 29.6% used)
Flash code: 75408 bytes
Flash rodata: 23844 bytes
Total image size:~ 146376 bytes (.bin may be padded larger)
Test 2
Total sizes:
DRAM .data size: 8320 bytes
DRAM .bss size: 4072 bytes
Used static DRAM: 12392 bytes ( 168344 available, 6.9% used)
Used static IRAM: 38804 bytes ( 92268 available, 29.6% used)
Flash code: 75240 bytes
Flash rodata: 23796 bytes
Total image size:~ 146160 bytes (.bin may be padded larger)
Test 3
Total sizes:
DRAM .data size: 8320 bytes
DRAM .bss size: 4072 bytes
Used static DRAM: 12392 bytes ( 168344 available, 6.9% used)
Used static IRAM: 38804 bytes ( 92268 available, 29.6% used)
Flash code: 75004 bytes
Flash rodata: 23780 bytes
Total image size:~ 145908 bytes (.bin may be padded larger)
Analysis
Size for code obtained by running stat --format="%s" main/main.c
All Sizes are in Bytes
Test No. | Code | Image | Flash Code | Flash rodata
-------- | -----| ------ | ---------- | ------------
1 | 207 | 146376 | 75408 | 23844
2 | 70 | 146160 | 75240 | 23796
3 | 43 | 145908 | 75004 | 23780
At least 145KB of boiler plate code just to get an empty main run.
Speculation
I suspect that the 145KB is made up of a number of libraries that are always loaded onto the chip whether you use them or not. Some of them must be the FreeRTOS, WiFi, HTTP etc.
Can we bring down this size somehow and load only the bare minimum required for operation?
