openc166

An open-source assembler for the Infineon C166 and C167 microcontroller family (including ST10 parts), compatible with the Keil A166 assembler.

It turns Keil-style assembly source into a raw binary image at a fixed address, or into an Intel HEX or Motorola S-record file. That suits small programs loaded into RAM or flash and started directly, such as ECU payloads, bootstrap loaders, and test code. No linker or object-file converter is needed.

openc166 runs on Linux, Windows and macOS. It needs only a C++20 compiler and CMake.

Status

Early development (version 0.x). What works today:

• The complete C166 and C167 instruction set, with all addressing modes. Every instruction form is checked byte for byte against Keil A166 V5.38: over 5,000 checks of code bytes, addresses and symbol values, all identical.
• Keil expression syntax: operators, HIGH/LOW, SOF/SEG/PAG/POF, BOF, DATA3/DATA4/DATA8/DATA16, character constants, bit addresses such as PSW.3 or 0FD00H.5, and extended-SFR checks inside EXTR sequences.
• Sections with an address (SECTION CODE AT 0E000H) and without one. openc166 places sections without AT as Keil's L166 linker would, or at addresses you give (--section NAME=ADDR), so code that leaves placement to the linker can still be assembled straight to a binary. DGROUP and CGROUP keep sections in one data page or code segment, as in L166. BIT sections and DBIT hold bit variables, placed bit by bit as L166 places them.
• PROC/ENDP, ORG, EVEN, EQU/SET/BIT, DB/DW/DD, DS/DSB/DSW/DSD, and DPPTR/DSPTR/DBPTR, including Keil's automatic alignment of word data.
• Segmented mode ($SEGMENTED): ASSUME, DPPn: prefixes, and Keil's rules for which data page register an address goes through.
• DEFR/DEFA/DEFB, the register-definition directives that register files use, with Keil's rules for repeated definitions.
• A built-in REG167.INC register file, written from Infineon's manuals, so $INCLUDE(REG167.INC) works without Keil installed.
• Keil's rules for label arithmetic, which decide between short and long instruction forms.
• Generic JMP and CALL: like Keil, openc166 picks the shortest instruction that reaches the target and shortens forward jumps over several passes. Label types (NEAR, FAR, WORD, ...) and the SHORT and type operators (FAR x, WORD PTR x, ...) work as in Keil.
• $INCLUDE and $INCDIR, with Keil's search order and listing format.
• Conditional assembly: $SET/$RESET, $IF/$ELSEIF/$ELSE/$ENDIF and the IF/ELSEIF/ELSE/ENDIF statements, with Keil's quirks (only bit 0 of a condition counts) and listing format.
• LIT text replacement (PORT LIT 'R2'), with Keil's rules for where names are replaced.
• Keil's standard macros: MACRO/ENDM with parameters and LOCAL labels, REPT, IRP, IRPC, EXITM, NUL, & and %, with Keil's rules for splitting arguments. $GEN/$NOGEN choose whether the listing shows expanded lines.
• The $MOD167, $CASE, $SEGMENTED and $TABS controls, with Keil's rule that these come before the first statement. Listing-only controls are accepted and ignored.
• Keil error and warning codes (A74, A111, ...), so messages line up with the Keil manual.
• Raw binary, Intel HEX and Motorola S-record output. The HEX records match Keil OH166's H167 format.
• Several source files linked into one program, as L166 does: EXTERN, PUBLIC and GLOBAL symbols, and sections of the same name combined across files. Each file is assembled separately (a "module"), so a name that is not PUBLIC stays private to its file.
• Register banks (REGBANK/REGDEF), placed in 0FC00H..0FDFFH as L166 places them, and the NAME, SSKDEF, PECDEF and TYPEDEC directives.
• TASKING sources (--dialect tasking): the common part of TASKING's m166 preprocessor (@SET, @EVAL, @IF/@ELSE/@ENDI, @DEFINED), TASKING's controls and STDNAMES register files, and the places where its assembler differs from Keil's. Infineon's MiniMon monitor and flash drivers, which gkflasher's ECU code comes from, rebuild byte for byte from their TASKING sources. See docs/tasking.md.
• A Python package and a C API, for tools that assemble code themselves.

Not done yet:

• Keil's MPL macro language (%DEFINE and the like); put $NOMPL at the top of the file to use % as text
• OMF-166 object files and libraries
• TASKING's m166 macros with parameters (@DEFINE), loops and string functions

See docs/compatibility.md for exact behaviour and the few places where openc166 deliberately differs from Keil.

Building

cmake -S . -B build
cmake --build build
ctest --test-dir build

The program is build/cli/openc166. On Windows with Visual Studio it is under build\cli\Debug\ or build\cli\Release\. The shared library with the C API is built in build/src/.

Usage

openc166 payload.a66                       # writes payload.bin
openc166 payload.a66 -o out.bin -l out.lst # choose names, add a listing
openc166 payload.a66 -o payload.hex        # Intel HEX
openc166 payload.a66 -o payload.s19        # S-records (S1)
openc166 main.a66 lib.a66 -o payload.bin   # link two source files

Several source files are linked into one program, the way Keil's L166 linker joins the object files of A166:

• An EXTERN name in one file takes the value of the PUBLIC or GLOBAL name in another. A name that no file exports is an error.
• Sections with the same name and class are joined into one: the parts of a PUBLIC or GLOBAL section follow one another, the parts of a COMMON section lie on top of each other.
• Without -o, the output is named after the first file. With -l, the listing has one part per file and a symbol table that names the file each symbol comes from.
• Code outside sections starts at --origin in every file, so normally each file puts its code in sections.

$INCLUDE looks in each file's own directory. docs/compatibility.md has the exact rules.

The output format follows the extension of the -o file: .hex, .h86 and .ihx give Intel HEX; .srec, .s19, .s28, .s37, .mot and .sx give S-records; anything else gives a raw binary. --format chooses it explicitly.

A raw binary starts at the lowest address used. For example, code in SECTION CODE AT 0E000H produces a file whose first byte belongs at 0E000H. Gaps between pieces of code are filled. HEX and S-record files carry the address of every record, so they hold only the bytes used.

Sections without AT go in order of first appearance to the first free, suitably aligned place from the origin on, as L166 places them by default. --section overrides that for chosen sections, like L166's SECTIONS control. The listing ends with a table of where each section went. examples/sections.a66 shows both.

Intel HEX files use extended linear address records (type 04) for addresses above 64 KB, like OH166 with its H167 option. S-records use S1, S2 or S3 records by extension (.s19, .s28, .s37); otherwise the smallest kind that holds every address.

The exit status is 0 on success, 1 on assembly errors (no output is written), and 2 for usage or file errors. Messages use the format file:line:column: error A74: ....

examples/payload.a66 is a short, commented example. examples/mtos/ holds real ECU payloads for Siemens SIMK43 ECUs, taken from gkflasher.

Python

pip install openc166     # or "pip install ." in a checkout

Wheels are published for Linux, Windows and macOS on x86 and ARM, including 32-bit and 64-bit Raspberry Pi OS (on a Raspberry Pi 2 or newer); other systems build from source, which needs CMake and a C++20 compiler. To get just the openc166 command, pipx install openc166 works too.

import openc166

result = openc166.assemble("""
$MOD167
PROG    SECTION CODE AT 0E000H
        MOV     R4, #0BEEFH
        RET
PROG    ENDS
        END
""")
image = result.image()     # raises openc166.AssemblyError if there are errors
image.base                 # 0xE000, the address of image.data[0]
image.data                 # b'\xe6\xf4\xef\xbe\xcb\x00'

• openc166.assemble(source, *, file_name=None, cpu=None, origin=0, include_dirs=(), sections=None, dialect="keil", controls=()) assembles a str or bytes. sections gives addresses for sections without AT, e.g. {"VARS": 0xF600}. dialect="tasking" reads TASKING source; controls is a list of controls read before the source, as with -c. openc166.assemble_file(path, ...) reads a file; $INCLUDE then also searches the file's directory.
• The result has ok, diagnostics (each with severity, code, message, file, line, column; str() gives the usual one-line message), errors, warnings, chunks (address and bytes of each piece of code), symbols (a dict of name to Symbol), symbol(name) (lookup ignoring case), sections (a dict of name to Section: type, align, address, size, and placement, which is "at", "given" or "located"), listing and cpu.
• openc166.assemble_many({"main.a66": text1, "lib.a66": text2}, ...) links several sources into one program, like several files on the command line; openc166.assemble_files([path1, path2], ...) reads them from files. Each Symbol then says which file defines it (module) and whether it is PUBLIC or GLOBAL (exported). result.modules lists the file names; result.symbols holds one symbol per name (the exported one if there is one), result.all_symbols all of them. Each Section has its class_name and group.
• result.image(base=None, fill=0xFF) lays all code out as one block, like the command-line tool.
• result.intel_hex(record_size=16) and result.srec(record_size=16, address_size=None) return Intel HEX and S-record text (address_size 2, 3 or 4 picks S1, S2 or S3 records).

The package needs Python 3.9 or newer. It also installs the openc166 command. It loads the library through ctypes, so one wheel works with every Python version.

C API

include/openc166/openc166.h declares a plain C interface, exported by the shared library (libopenc166.so, libopenc166.dylib or openc166.dll). Any language that can call C can use it: oc166_assemble assembles one source, oc166_assemble_many links several. The header documents every function; the Python package is an example of a complete binding.

Testing

• ctest --test-dir build runs the unit tests, the C API test and the Python package tests, and assembles the examples, checking every byte.

• tests/acceptance/minimon.py rebuilds Infineon's MiniMon from its TASKING sources and compares the result with its HEX files. MiniMon is not included; set MINIMON_DIR to its directory (the one that holds MCPROG and Driver) and ctest runs it too.

• tests/diff/ contains the differential test against Keil A166. Keil is not included. If you have your own copy, run:

  KEIL_A166=/path/to/A166.EXE python3 tests/diff/keil_diff.py tests/diff/cases/*.a66
  

  It compares every line: address, code bytes, warnings and errors, and the final value of every symbol. Add --image to also link Keil's output with L166 and OH166 and compare the complete memory image, and --codes to list lines where both assemblers report an error but with different codes. Lines marked ; DIVERGES: are deliberate differences (see docs/compatibility.md) and are skipped.

  Given a directory instead of a file, it treats each .a66 file in it as one module, links Keil's objects with L166, and compares the linked image and the linker's errors with openc166's:

  KEIL_A166=/path/to/A166.EXE python3 tests/diff/keil_diff.py tests/diff/cases/link/*/
  

  On Linux and macOS, Keil runs under Wine. To generate test lines that cover the whole instruction set, run tests/diff/gen_sweep.py build/generated/openc166/isa.json c167 > sweep.a66.

  The test inputs were written independently for this project. Keil's output is used only for the local comparison and is never stored in the repository.

License

MIT; see LICENSE. The bundled doctest test framework is also MIT.

openc166 is not affiliated with Arm/Keil or Infineon. "Keil", "A166", "C166", "C167" and "TASKING" are trademarks of their respective owners. The names are used only to describe compatibility.