Reducing memory footprint when only listening for Advertisements

[Bascy]

Hi,

In our project we only use BLE to listen for advertisements from registered devices. Currently, when calling BleDevice::init() it takes around 70k of memory.

Is it possible to reduce the memory footprint in our use case?

[h2zero]

Have you changed your config to disable the unused roles?

#define CONFIG_BT_NIMBLE_ROLE_CENTRAL 0
#define CONFIG_BT_NIMBLE_ROLE_PERIPHERAL 0
#define CONFIG_BT_NIMBLE_ROLE_BROADCASTER 0

Also other unused config options might save some RAM, but those are the biggest.

[Bascy]

Getting linker errors when i set those config options in nimconfig.h:

C:/Users/bas/.platformio/packages/toolchain-xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: .pio/build/esp32dev/lib08e/NimBLE-Arduino/nimble/nimble/host/src/ble_hs_resolv.c.o:(.literal.ble_hs_resolv_gen_priv_addr+0x0): undefined reference to `na_ble_sm_alg_encrypt'
C:/Users/bas/.platformio/packages/toolchain-xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: .pio/build/esp32dev/lib08e/NimBLE-Arduino/nimble/nimble/host/src/ble_hs_resolv.c.o: in function `ble_hs_resolv_gen_priv_addr':
D:\Experiments\pio version experiments/.pio/libdeps/esp32dev/NimBLE-Arduino/src/nimble/nimble/host/src/ble_hs_resolv.c:410:(.text.ble_hs_resolv_gen_priv_addr+0xa8): undefined reference to `na_ble_sm_alg_encrypt'
C:/Users/bas/.platformio/packages/toolchain-xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: .pio/build/esp32dev/lib08e/NimBLE-Arduino/nimble/nimble/host/src/ble_hs_resolv.c.o: in function `ble_hs_resolv_rpa':
D:\Experiments\pio version experiments/.pio/libdeps/esp32dev/NimBLE-Arduino/src/nimble/nimble/host/src/ble_hs_resolv.c:769:(.text.ble_hs_resolv_rpa+0x79): undefined reference to `na_ble_sm_alg_encrypt'
collect2.exe: error: ld returned 1 exit status
*** [.pio\build\esp32dev\firmware.elf] Error 1

[h2zero]

Please update your lib version, that issue was fixed a while ago.

[Bascy]

I am using the latest version 2.3.7

[h2zero]

Hmm, looks like it builds for the C6 but not the original esp32.
It will build if you leave CONFIG_BT_NIMBLE_ROLE_CENTRAL enabled.

[Bascy]

I cleaned all and started again:

With CONFIG_BT_NIMBLE_ROLE_PERIPHERAL=0 its working, gaining 264 bytes

With CONFIG_BT_NIMBLE_ROLE_CENTRAL=0 its working, gaining 520 bytes

With both PERIPHERAL and CENTRAL I get linker error:

C:/Users/bas/.platformio/packages/toolchain-xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: .pio/build/esp32dev/lib08e/NimBLE-Arduino/nimble/nimble/host/src/ble_hs_resolv.c.o:(.literal.ble_hs_resolv_gen_priv_addr+0x0): undefined reference to `na_ble_sm_alg_encrypt'
C:/Users/bas/.platformio/packages/toolchain-xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: .pio/build/esp32dev/lib08e/NimBLE-Arduino/nimble/nimble/host/src/ble_hs_resolv.c.o: in function `ble_hs_resolv_gen_priv_addr':
D:\Experiments\pio version experiments/.pio/libdeps/esp32dev/NimBLE-Arduino/src/nimble/nimble/host/src/ble_hs_resolv.c:410:(.text.ble_hs_resolv_gen_priv_addr+0xa8): undefined reference to `na_ble_sm_alg_encrypt'
C:/Users/bas/.platformio/packages/toolchain-xtensa-esp-elf/bin/../lib/gcc/xtensa-esp-elf/14.2.0/../../../../xtensa-esp-elf/bin/ld.exe: .pio/build/esp32dev/lib08e/NimBLE-Arduino/nimble/nimble/host/src/ble_hs_resolv.c.o: in function `ble_hs_resolv_rpa':
D:\Experiments\pio version experiments/.pio/libdeps/esp32dev/NimBLE-Arduino/src/nimble/nimble/host/src/ble_hs_resolv.c:769:(.text.ble_hs_resolv_rpa+0x79): undefined reference to `na_ble_sm_alg_encrypt'
collect2.exe: error: ld returned 1 exit status

With CONFIG_BT_NIMBLE_ROLE_BROADCASTER=0 I get a compile error

.pio/libdeps/esp32dev/NimBLE-Arduino/src/NimBLEServer.cpp: In static member function 'static int NimBLEServer::handleGapEvent(ble_gap_event*, void*)':
.pio/libdeps/esp32dev/NimBLE-Arduino/src/NimBLEServer.cpp:425:26: error: 'class NimBLEServer' has no member named 'startAdvertising'
  425 |                 pServer->startAdvertising();
      |                          ^~~~~~~~~~~~~~~~

[h2zero]

Yeah, the NimBLE core needs to be updated, probably won't be fixed until 3.x release.
Doesn't seem to save much anyway, the stack takes a good amount of RAM.