dawnpy-modbus

Modbus transport extension for dawnpy. Provides the dawnpy-modbus CLI for talking to Dawn devices over Modbus RTU.

Installation

Requires the core dawnpy package to be installed first:

pip install -e tools/dawnpy-modbus

Dependencies (installed automatically): dawnpy, click >= 8.1, pymodbus >= 3.1, < 4.

Command

dawnpy-modbus /dev/ttyUSB0 device1/descriptor.yaml device2/descriptor.yaml
dawnpy-modbus --help

The command requires a serial path followed by one or more descriptor paths. Each descriptor describes one Modbus node for descriptor-aware multi-node access.

Common options:

--baudrate N: serial baudrate. Defaults to 115200.
--parity N|O|E: serial parity. Defaults to even parity.
--stopbits 1|2: serial stop bits. Defaults to 1.
--timeout SECONDS: serial timeout. Defaults to 1.0.
--unit N: Modbus slave address. Defaults to 1.
--kconfig-var SYMBOL and --kconfig-values VALUES: apply Kconfig-derived object ID overrides to descriptor instances.
--debug / --no-debug: enable verbose protocol logging.

Console

The interactive console shares the command set documented in Interactive Console Commands (see dawnpy-serial).

Dawn Modbus register addresses are used exactly as declared in the descriptor register map; the console does not apply 1-based Modbus offset conversion. Seekable Dawn IOs are exposed through holding registers and the client reads those windows in multiple chunks when the declared window is larger than the single-request pymodbus limit.

The CLI mirrors the Modbus wire contract documented by Dawn’s Modbus protocols: it does not define the data layout itself, it only decodes and encodes values using the protocol’s register and byte-order rules.

For single-binding holding/input groups whose runtime width is larger than what the descriptor alone can prove (for example board ADCs whose channel count is selected by the target), the client probes for the full register width after an exception-4 short read and then decodes the payload as a vector of dtype-sized elements.

Tests

cd tools/dawnpy-modbus && tox
tox -e py        # tests + coverage
tox -e format    # formatting check
tox -e flake8    # linting
tox -e type      # type checking