How to reduce the size of an executable file?

[msu7xi]

Hello,

I have modified the central_uart example to make the nRF52832 communicate with an ESP32 in MessagePack. After having disabled the logger configuration in the proj.conf file the size of the *.bin file is 225.8 kB which is too large for an nRF52805 (flash of 192 kB). Is there any way to reduce the bin file size?

Below the proj.conf file:

#
# Copyright (c) 2018 Nordic Semiconductor
#
# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
#

# Enable the UART driver
CONFIG_UART_ASYNC_API=y
CONFIG_NRFX_UARTE0=y
CONFIG_SERIAL=y
CONFIG_CONSOLE=y
CONFIG_UART_CONSOLE=y

# Enable the BLE stack with GATT Client configuration
CONFIG_BT=y
CONFIG_BT_CENTRAL=y
CONFIG_BT_SMP=y
CONFIG_BT_GATT_CLIENT=y

# Enable the BLE modules from NCS
CONFIG_BT_NUS_CLIENT=y
CONFIG_BT_SCAN=y
CONFIG_BT_SCAN_FILTER_ENABLE=y
CONFIG_BT_SCAN_UUID_CNT=1
CONFIG_BT_SCAN_ADDRESS_CNT=1
CONFIG_BT_GATT_DM=y
CONFIG_HEAP_MEM_POOL_SIZE=2048
CONFIG_BT_MAX_PAIRED=1
CONFIG_BT_MAX_CONN=1

# This example requires more workqueue stack
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048

# Enable bonding
CONFIG_BT_SETTINGS=y
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y
CONFIG_NVS=y
CONFIG_SETTINGS=y

# Enable use of the non-minimal C functionality (stdio.h).
CONFIG_NEWLIB_LIBC=y

# Config logger
CONFIG_LOG=n
CONFIG_USE_SEGGER_RTT=y
CONFIG_LOG_BACKEND_RTT=n
CONFIG_LOG_BACKEND_UART=n
CONFIG_LOG_PRINTK=n
CONFIG_BT_DEBUG_LOG=n
CONFIG_BT_GATT_DM_DATA_PRINT=n

CONFIG_ASSERT=y

# Config I2C
CONFIG_GPIO=y
CONFIG_I2C=y
CONFIG_I2C_NRFX=y

CONFIG_SHELL=y
CONFIG_I2C_SHELL=y

Regards,

Marco

[JamesDougherty]

Hey Marco,

Just curious, have you tried using CONFIG_SIZE_OPTIMIZATIONS=y so GCC optimizes for size? That may work. Also, have you tried using the minimal C library (CONFIG_MINIMAL_LIBC=y) instead of Newlib (CONFIG_NEWLIB_LIBC=y)?

[Hieu]

Hi Marco,

The suggestions that JamesDougherty suggested are all good.

We also provide a documentation page on this topic that you could refer to: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.4.1/nrf/app_dev/optimizing/memory.html.

Additionally, you can refer to prj_minimal.conf from the Peripheral UART samples for other Kconfig's that you could turn on/off to save image size.

Please note that adding OTA DFU will require enough flash to fit at least 2x the application, 1x MCUboot bootloader, and a small amount for other overheads. With wired recovery DFU method, it can be reduced to 1x application, 1x bootloader size, and overheads. 

Regards,

Hieu

[msu7xi]

Hello James,

Yes, I'm using CONFIG_SIZE_OPTIMIZATIONS=y but I have not tried CONFIG_MINIMAL_LIBC=y yet. Should this be configured in the prj.conf file?

[JamesDougherty]

Hey Marco,

Yeah. Comment out the CONFIG_NEWLIB_LIBC=y line and it will default to the minimal library. Of course you can add CONFIG_MINIMAL_LIBC=y just for your own reference, but CONFIG_MINIMAL_LIBC=y should be enabled if CONFIG_NEWLIB_LIBC and CONFIG_EXTERNAL_LIBC are not specified.

[JamesDougherty]

I should mention too, you're using the full version of the C library. If you need Newlib C for a specific reason, then you can try using the size optimized version of it. You can try this by leaving CONFIG_NEWLIB_LIBC=y enabled, but also enabling CONFIG_NEWLIB_LIBC_NANO=y as well. You can read more about it here: https://docs.zephyrproject.org/latest/develop/languages/c/newlib.html#nano-newlib