Standard libraries, like printf(), aren't working / available

[AaronM0]

Device: nRF51822_xxac; the Nordic-supplied NUS application worked after I figured out the softdevice and application loading sequence.

Development platform: Mac OS Tahoe 26.3; Toolchain: Arm GNU Toolchain 14.3.1, downloaded from https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads 

I'm in the "blink an LED" / see if it works stage of changing the UART NUS application, and haven't actually changed anything in the ble_peripheral/ble_app_uart application, except for DEVICE_NAME: I'm just testing that my build tools can correctly produce an output.  It's sort-of working, but the "printf( "UART start!" );" isn't working.  The binary builds, and the "make flash_softdevice && make flash" seem to work; I can see and connect to the updated DEVICE_NAME in the BLE scan tool, but the program serial output via printf() doesn't print.  Here's the build output:

$ make && make flash_softdevice && make flash
Compiling file: main.c
Linking target: _build/nrf51822_xxac.out
/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/bin/ld: /Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc_nano.a(libc_a-closer.o): in function `_close_r':
closer.c:(.text._close_r+0xc): warning: _close is not implemented and will always fail
/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/bin/ld: /Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc_nano.a(libc_a-closer.o): note: the message above does not take linker garbage collection into account
/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/bin/ld: /Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc_nano.a(libc_a-lseekr.o): in function `_lseek_r':
lseekr.c:(.text._lseek_r+0x10): warning: _lseek is not implemented and will always fail
/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/bin/ld: /Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc_nano.a(libc_a-lseekr.o): note: the message above does not take linker garbage collection into account
/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/bin/ld: /Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc_nano.a(libc_a-readr.o): in function `_read_r':
readr.c:(.text._read_r+0x10): warning: _read is not implemented and will always fail
/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/bin/ld: /Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc_nano.a(libc_a-readr.o): note: the message above does not take linker garbage collection into account
/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/bin/ld: /Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc_nano.a(libc_a-writer.o): in function `_write_r':
writer.c:(.text._write_r+0x10): warning: _write is not implemented and will always fail
/Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/bin/ld: /Applications/ArmGNUToolchain/14.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/14.3.1/../../../../arm-none-eabi/lib/thumb/v6-m/nofp/libc_nano.a(libc_a-writer.o): note: the message above does not take linker garbage collection into account

text data bss dec hex filename
 20584 136 2208 22928 5990 _build/nrf51822_xxac.out

Preparing: _build/nrf51822_xxac.hex
Preparing: _build/nrf51822_xxac.bin
Flashing: s130_nrf51_2.0.1_softdevice.hex
nrfjprog --jdll /Applications/SEGGER/JLink_V890/libjlinkarm.8.90.0.dylib --program /Users/aaronm/Downloads/NordicSemi-nRF51822/nRF5_SDK_12.3.0_d7731ad/components/softdevice/s130/hex/s130_nrf51_2.0.1_softdevice.hex -f nrf51 --sectorerase
[ #################### ] 4.232s | Erase file - Done erasing
[ #################### ] 1.469s | Program file - Done programming
WARNING: A programming operation has been performed without --verify.
WARNING: Programming can fail without error.
nrfjprog --jdll /Applications/SEGGER/JLink_V890/libjlinkarm.8.90.0.dylib --reset -f nrf51
Applying system reset.
Run.
Flashing: _build/nrf51822_xxac.hex
nrfjprog --jdll /Applications/SEGGER/JLink_V890/libjlinkarm.8.90.0.dylib --program _build/nrf51822_xxac.hex -f nrf51 --sectorerase
[ #################### ] 0.807s | Erase file - Done erasing
[ #################### ] 0.283s | Program file - Done programming
WARNING: A programming operation has been performed without --verify.
WARNING: Programming can fail without error.
nrfjprog --jdll /Applications/SEGGER/JLink_V890/libjlinkarm.8.90.0.dylib --reset -f nrf51
Applying system reset.
Run.

I disabled #define RETARGET_ENABLED 0 to get it to compile; it wouldn't complete the linking phase at all with RETARGET set to 1.  I suspect the "LDFLAGS += --specs=nano.specs -lc -lnosys" has something to do with the missing printf() and related libraries, but I'm not wizard enough to determine how.  Hopefully, this is a trivial issue for the more experienced among us.

Thanks!

[AaronM0]

Sorry - forgot the SoftDevice and SDK versions:

S130: Bluetooth 4.2 version 2.0.1

nRF5 SDK version 12.3.0

[Simonr]

Hi Aaron

It sounds like your application is working as expected, but that you don't get the logging you expect. Are you working on a development kit or a custom board here? If a custom board, how is the device connected to your computer and how is the serial data going to the computer's serial terminal?

Best regards,

Simon

[AaronM0]

It's an old Red Bear Nano *1, which uses a RayTec MDBT40 *2 module, which I bought years ago and never did anything with.  And logging / printf() does work with the Nordic hex files for the NUS UART example, but not with the UART hex built locally.

I tried:

official SD & local UART hex - no logging

official SD & official UART hex - logging

And this is reproducible.  So it looks like my compiled version of the UART hex doesn't have the standard libraries for printing.

https://os.mbed.com/platforms/RedBearLab-BLE-Nano/

https://www.tinyosshop.com/mdbt40-ble-module 

Aside from pathnames to SDK_ROOT, the Makefile is taken straight from the SDK.  Here's the linker section:

# Linker flags
LDFLAGS += -mthumb -mabi=aapcs -L $(TEMPLATE_PATH) -T$(LINKER_SCRIPT)
LDFLAGS += -mcpu=cortex-m0
# let linker to dump unused sections
LDFLAGS += -Wl,--gc-sections
# use newlib in nano version
LDFLAGS += --specs=nano.specs -lc -lnosys

[Simonr]

Hi

Sorry about the late reply, but I'm still working through the backlog after the Easter holiday.

I asked a colleague with more experience with the GNU toolchain, and here are some thoughts.

Using a newer GCC version with this old of an SDK will likely lead to multiple problems, that might explain why you have issues with your generated .hex file. For the printf explicitly, the fact that you disabled #define RETARGET_ENABLED 0 to get it to compile, explains why printf() doesn't work. Without this, retarget.c won't be compiled, which is what redirects any printf() functions to UART.

Most likely you need to port the retarget.c implementation to work with the newlib version in this newer toolchain. Exactly what needs to be changed is hard to say since you haven't posted the build errors when RETARGET_ENABLED = 1.

Best regards,

Simon