Uno R4 WiFi bootloader built w/ latest GCC corrupted on first sketch upload due to >16 kB size

[lookfwd]

Summary

Using the latest linux build tools (arm-none-eabi-gcc (15:14.2.rel1-1) 14.2.1 20241119) and following the build instructions in the README produces a dfu_wifi.hex that is 17,017 bytes of code, exceeding the 16 KB (0x4000) bootloader region assumed by ArduinoCore-renesas. When a sketch is subsequently uploaded, the application's flash erase wipes the tail end of the bootloader, permanently bricking it. For comparison, the dfu_wifi.hex shipped in the directory, is 15,400 bytes.

Observed output

   text    data     bss     dec     hex filename
  17017       0   19092   36109   8d0d _build/uno_r4/arduino-renesas-bootloader.elf

The resulting hex covers 0x00000000..0x00004279 in code flash, overflowing the 16 KB region by 633 bytes (0x279). It also emits records at 0x01010000 (OFS / option-setting memory), which the shipped bootloader does not.

Expected output

A text size under 16384 bytes, comparable to the shipped dfu_wifi.hex (15,400 bytes), with no records outside the 16 KB code region.

Suggestions

1. Manually downgrading to tooling version 10.3 (gcc-arm-none-eabi-10.3-2021.10) reduces the size to the expected levels.
2. A post-build size assertion on each Makefile that fails if text > 16384 would catch such errors
3. Document if you manually strip the OFS region (0x01010000+) emitted by the linker script, or create the .hex out of the .bin which would produce the clean .hexs I see in the prebuilt section (arm-none-eabi-objcopy -I binary -O ihex --change-addresses=0x00000000 arduino-renesas-bootloader.bin arduino-renesas-bootloader-clean.hex)

[maidnl]

@lookfwd thank you for submitting this issue, but I am unable to reproduce the problem.
I am using official ARM toolchains (https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads)

Here is what I get.

With version 14.2:
arm-none-eabi-gcc --version outputs arm-none-eabi-gcc (Arm GNU Toolchain 14.2.Rel1 (Build arm-14.52)) 14.2.1 20241119

and I get the following results:
TINYUSB_ROOT=$PWD/../tinyusb make -f Makefile.wifi outputs

   text    data     bss     dec     hex filename
  15357       0   19096   34453    8695 _build/uno_r4/arduino-renesas-bootloader.elf

I also tried with the newest version 15.2:
arm-none-eabi-gcc --version
arm-none-eabi-gcc (Arm GNU Toolchain 15.2.Rel1 (Build arm-15.86)) 15.2.1 20251203

and I get:

 text    data     bss     dec     hex filename
  15373       0   19096   34469    86a5 _build/uno_r4/arduino-renesas-bootloader.elf

The "signature" of your compiler version looks a little bit different from mine so maybe is something related to that. Would you please check and let us know? Thank you

[lookfwd]

Hello @maidnl,

thanks for trying to reproduce this.

I'm starting with an empty Ubuntu box in AWS and I follow the steps here.

./compile.sh
/bin/sh: 1: arm-none-eabi-gcc: not found

So there's no compiler at that point. I install...

sudo apt install gcc-arm-none-eabi
...
Unpacking gcc-arm-none-eabi (15:14.2.rel1-1) ...

Now the version very close to what you also use is available 14.2.1 20241119. I don't see the "(Arm GNU Toolchain 14.2.Rel1 (Build arm-14.52))" that is on your --version though:

$ arm-none-eabi-gcc --version
arm-none-eabi-gcc (15:14.2.rel1-1) 14.2.1 20241119
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Then I compile and I get the longer .hex as described previously:

./compile.sh
...
   text	   data	    bss	    dec	    hex	filename
  17017	      0	  19092	  36109	   8d0d	_build/uno_r4/arduino-renesas-bootloader.elf
...
$ tail -10 distrib/dfu_wifi.hex 
:10421C0068000000D000000000000000000000005A
:10422C000000000000000000000000000000000082
:10423C000000000000000000000000000000000072
:10424C000000000000000000000000000000000062
:04425C00000000005E
:020000040101F8
:10001800FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE8
:0C002800FFFFFFFFFFFFFFFFFFFFFFFFD8
:04000003000015F1F3
:00000001FF

I go to the ARM page. I download arm-gnu-toolchain-14.2.rel1-x86_64-arm-none-eabi.tar.xz. I extract and update PATH.

$ arm-none-eabi-gcc --version
arm-none-eabi-gcc (Arm GNU Toolchain 14.2.Rel1 (Build arm-14.52)) 14.2.1 20241119
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

./compile.sh
...
   text	   data	    bss	    dec	    hex	filename
  15357	      0	  19096	  34453	   8695	_build/uno_r4/arduino-renesas-bootloader.elf
...
$ tail -10 distrib/dfu_wifi.hex 
:103BA00068000000D00000000000000000000000DD
:103BB0000000000000000000000000000000000005
:103BC00000000000000000000000000000000000F5
:103BD00000000000000000000000000000000000E5
:043BE00000000000E1
:020000040101F8
:10001800FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE8
:0C002800FFFFFFFFFFFFFFFFFFFFFFFFD8
:04000003000015F1F3
:00000001FF

I also used the latest version (15.2) from ARM.

$ arm-none-eabi-gcc --version
arm-none-eabi-gcc (Arm GNU Toolchain 15.2.Rel1 (Build arm-15.86)) 15.2.1 20251203
Copyright (C) 2025 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

./compile.sh
...
   text	   data	    bss	    dec	    hex	filename
  15373	      0	  19096	  34469	   86a5	_build/uno_r4/arduino-renesas-bootloader.elf
...
$ tail -10 distrib/dfu_wifi.hex 
:103BB00068000000D00000000000000000000000CD
:103BC00000000000000000000000000000000000F5
:103BD00000000000000000000000000000000000E5
:103BE00000000000000000000000000000000000D5
:043BF00000000000D1
:020000040101F8
:10001800FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE8
:0C002800FFFFFFFFFFFFFFFFFFFFFFFFD8
:04000003000015D50F
:00000001FF

I think we can conclude that what is described in the instructions doesn't define a workflow that gives a single outcome. Of course, if you document that you only compile using the ARM compilers, and you trust that the size won't change a lot with their next compiler release, as it happens with the Ubuntu compiler, everything is ok.

But I think the suggestions remain:

• Manually downgrading to tooling version 10.3 (gcc-arm-none-eabi-10.3-2021.10) reduces the size to the expected levels. Document the compiler versions that produce functional binaries (<16 KB (0x4000)).
• Since the 0x4000 is a system constraint a post-build size assertion on each Makefile that fails if text > 16384 would catch corrupt .hex's as people keep compiling with newer compilers.
• As you can observe both .hexs try to write to 0x0101 and that's not the format of the .hexs you provide. As such, document if you manually strip the OFS region (0x01010000+) emitted by the linker script (unlikely), or create the .hex out of the .bin (highly likely) which would produce the clean .hexs I see in the prebuilt section (arm-none-eabi-objcopy -I binary -O ihex --change-addresses=0x00000000 arduino-renesas-bootloader.bin arduino-renesas-bootloader-clean.hex)

[maidnl]

Hello @lookfwd,
I understand your concerns and I strongly agree about the lack of checks on the resulting compilation artifacts.
I made this PR (https://github.com/arduino/arduino-renesas-bootloader/pull/9/changes) that introduce a new compilation script that tries to check the toolchain and in any case check the dimension of the binaries, informing the user if something goes wrong. This should also make the compilation process more predictable.

[lookfwd]

Thanks @maidnl! Will try it today

[lookfwd]

Hello @maidnl

It worked great, with a couple of minor usability issues. Here's what I reproduced:

$ ./compile-bootloader.sh R4-wifi
===================================================
WORKSPACE SETUP
Detected execution from INSIDE the arduino-renesas-bootloader repository.
tinyusb will be cloned directly into this folder:
-> /home/ubuntu/arduino-renesas-bootloader
Proceeding automatically...
===================================================
Error: arm-none-eabi-gcc not found in PATH.

$ sudo apt install gcc-arm-none-eabi

...

$ ./compile-bootloader.sh R4-wifi
===================================================
WORKSPACE SETUP
Detected execution from INSIDE the arduino-renesas-bootloader repository.
tinyusb will be cloned directly into this folder:
-> /home/ubuntu/arduino-renesas-bootloader
Proceeding automatically...
===================================================
Current Compiler: arm-none-eabi-gcc (15:14.2.rel1-1) 14.2.1 20241119
---------------------------------------------------
WARNING: Unable to determine if this is an official ARM compiler.
You should use an official ARM compiler that can be downloaded from here:
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
---------------------------------------------------
Do you want to continue the process with the current compiler? (y/N): y
Continuing compilation...
===================================================

...

Getting tinyusb dependencies...
./compile-bootloader.sh: line 107: python: command not found

...

   44 | #include "bsp_api.h"
      |          ^~~~~~~~~~~
compilation terminated.
make: *** [/home/ubuntu/arduino-renesas-bootloader/tinyusb/examples/build_system/make/toolchain/gcc_rules.mk:54: _build/uno_r4/obj/src/portable/renesas/rusb2/dcd_rusb2.o] Error 1
./compile-bootloader.sh: line 151: _build/uno_r4/arduino-renesas-bootloader.bin: No such file or directory
./compile-bootloader.sh: line 153: [: : integer expected
FAILED: Bootloader compilation failed for dfu_wifi.hex.
Reason: The .bin file is too big ( bytes). Maximum allowed is 16384 bytes.
Please switch to an ARM based build before attempting again.
clean up build folder

What I see here is that "bsp_api.h" can't be found, but the size check triggered, not because of the size, but because the '.bin' file doesn't exist:

./compile-bootloader.sh: line 151: _build/uno_r4/arduino-renesas-bootloader.bin: No such file or directory
./compile-bootloader.sh: line 153: [: : integer expected
FAILED: Bootloader compilation failed for dfu_wifi.hex.
Reason: The .bin file is too big ( bytes). Maximum allowed is 16384 bytes.
Please switch to an ARM based build before attempting again.
clean up build folder

It might be a bit confusing to show the check fail every time compilation fails for other reasons. The real reason the bsp_api.h doesn't exist can be found a bit earlier:

Getting tinyusb dependencies...
./compile-bootloader.sh: line 107: python: command not found

An empty ubuntu uses python3instead. I edit the script to use python3 and I get a wonderful output:

FAILED: Bootloader compilation failed for dfu_wifi.hex.
Reason: The .bin file is too big (16992 bytes). Maximum allowed is 16384 bytes.
Please switch to an ARM based build before attempting again.
clean up build folder

I then clean, wget https://developer.arm.com/.../arm-gnu-toolchain-15.2.rel1-x86_64-arm-none-eabi.tar.xz and rerun the script:

and I get

Size check passed: .bin file is 15348 bytes (Limit: 16384 bytes).
SUCCESS: Process successfully completed.
You can find the new bootloader 'dfu_wifi.hex' in the distrib sub-folder under arduino-renesas-bootloader.
clean up build folder
===================================================
Script execution finished.

The hex file is a nice clean hex file.

[maidnl]

Hi @lookfwd ,

thank you for your thorough testing and suggestions. I made 2 small changes to the script that should address your suggestions.