bin-cross-modem

Cross-compile & deploy tooling for VNPT fiber modem series running embedded Linux. Supports three modem models across MIPS, ARMv7, and AArch64 — each with a dedicated Python build script, Makefile, and hardware reference notes.

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Modem Models

Directory	Model	Architecture	C Library	Kernel	Access
h-cross/	VNPT HG1040-H	MIPS 34Kc big-endian	uClibc 0.9.33.2	2.6.36	Telnet 23
ns-cross/	VNPT 040-NS	ARM Cortex-A53 AArch32	glibc 2.22	4.4.115	SSH 22
xgs-cross/	VNPT XSW240-N (050-XGS)	ARM Cortex-A53 AArch64	glibc 2.32	5.4.55	Telnet 23

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Quick Start

Each subdirectory is self-contained. Pick the one matching your modem.

Using the Python script (recommended)

# First-time: check or install the cross-compiler
python h_build.py setup        # H modem
python ns_build.py setup       # NS modem
python xgs_build.py setup      # XGS modem

# Set your device address (saves to .hm / .ns / .xgs config file)
python h_build.py config --save -H YOUR_MODEM_IP -U admin -P YOUR_PASSWORD

# Build + upload + run in one step
python h_build.py deploy hello.c

# Build only
python h_build.py build hello.c

# Interactive shell on device
python h_build.py shell

Using make

cd h-cross
make                          # build (static, stripped)
make deploy                   # build + upload + run
make DEVICE=YOUR_IP deploy    # with explicit device address
make shell                    # interactive shell
make help                     # all targets and variables

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Device Configuration

Credentials are resolved in this order for each script:

CLI flags  (-H / -U / -P)
  → environment variables  (H_HOST / H_USER / H_PASS, etc.)
  → config file  (.hm, .ns, or .xgs in current directory)
  → built-in defaults  (set YOUR_MODEM_IP / YOUR_PASSWORD in the script)

To save config persistently:

python h_build.py config --save -H YOUR_MODEM_IP -U admin -P YOUR_PASSWORD

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Upload Methods

Each modem uses a different upload strategy (no FTP — device bftpd writes to flash on PUT):

Modem	Primary	Fallback
H (MIPS)	echo-hex over telnet	TFTP server on host
NS (AArch32)	echo-hex over SSH	HTTP server + device wget
XGS (AArch64)	HTTP server + device wget	base64 over telnet

The download subcommand fetches a URL to the device:

# H modem: host fetches URL, relays to device (H has no wget/curl)
python h_build.py download https://example.com/tool

# NS / XGS: device fetches directly via wget/curl
python ns_build.py download https://example.com/tool
python xgs_build.py download https://example.com/tool

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Critical Compiler Notes

H modem (MIPS big-endian)

• -msoft-float is required — EN751221 kernel has no hardware FPU. FPU instructions → SIGILL.
• -static is strongly recommended — device uses uClibc 0.9.33.2; glibc/musl dynamic binaries will not run.
• Use mips-* toolchain (big-endian), never mipsel-* (little-endian).

NS modem (AArch32)

• -mfloat-abi=soft is required — kernel 4.4.115 built without CONFIG_VFP. VFP instructions → SIGILL.
• Do NOT use -mfloat-abi=softfp — it silently emits VFP compute instructions → SIGILL.
• Use arm-linux-gnueabi (soft-float), never arm-linux-gnueabihf (wrong dynamic linker).

XGS modem (AArch64)

• Standard AArch64 — hardware FP enabled by default, no special float flags needed.
• Dynamic builds work fine (glibc 2.32 on device).

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Toolchain Installation

macOS

# H modem (MIPS big-endian) — LLVM/clang + muslsf sysroot
brew install llvm lld@20
curl -L https://musl.cc/mips-linux-muslsf-cross.tgz | tar xz -C /opt/homebrew/opt/
# h_build.py auto-detects this combination

# NS modem (AArch32 soft-float)
brew tap messense/macos-cross-toolchains
brew install arm-unknown-linux-gnueabi

# XGS modem (AArch64)
brew install aarch64-unknown-linux-gnu

Linux (Ubuntu/Debian)

sudo apt-get install gcc-mips-linux-gnu binutils-mips-linux-gnu        # H modem
sudo apt-get install gcc-arm-linux-gnueabi binutils-arm-linux-gnueabi  # NS modem
sudo apt-get install gcc-aarch64-linux-gnu binutils-aarch64-linux-gnu  # XGS modem

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Repository Structure

bin-cross-modem/
├── README.md
├── .gitignore
├── test_optim.c          # cross-platform correctness + perf test (all 3 targets)
│
├── h-cross/
│   ├── h_build.py        # build / upload / run script for H modem
│   ├── Makefile
│   ├── hello.c           # minimal test binary
│   └── NOTES.md          # hardware reference, toolchain details, library list
│
├── ns-cross/
│   ├── ns_build.py       # build / upload / run script for NS modem
│   ├── Makefile
│   ├── hello.c
│   ├── test.c
│   └── NOTES.md
│
└── xgs-cross/
    ├── xgs_build.py      # build / upload / run script for XGS modem
    ├── Makefile
    ├── hello.c
    └── NOTES.md

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NOTES.md Files

Each NOTES.md contains confirmed hardware data collected from live devices:

• CPU / SoC identification, exact RAM, kernel version, build toolchain
• Complete toolchain selection guide with ABI pitfalls
• Upload method details and writable directory inventory
• Full library list (/lib/*.so) with link flags and documentation links
• System parameters: socket buffers, resource limits, open ports, MTD layout
• C coding guide for the specific architecture (alignment, endianness, kernel limits)
• Performance optimization guide with hardware-specific compiler flags

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License

MIT