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hart-sim simulates HART field devices, a pressure and a temperature transmitter, that speak HART-IP over TCP and UDP on port 5094. Develop and test control-system links, asset management, commissioning scripts and gateways without devices, a HART modem or a commercial simulator, also in CI.

What it is for

• Developing HART software without a device on the bench. Anything that speaks HART-IP can talk to it.
• Running HART code in CI. A new bench for every test, in a pytest fixture or as a background process.
• Testing the unhappy paths. Sensor failure, saturation, busy, communication errors, missing answers and drift, switched on at runtime.
• Getting the details right. The process value becomes a 4-20 mA loop current with saturation and NAMUR NE 43 alarm currents. A bad checksum or a wrong address gets no answer, never a lenient guess.

Where to start

If you want to …	read
install it and read a first value	Getting started
change a device or write your own	Device profiles
use it in pytest and CI pipelines	Testing in CI
check that your code copes with misbehaving devices	Fault injection recipes
find out why something does not answer	Troubleshooting

The README is the complete reference: all commands, the profile format, the control channel, the limitations. This wiki adds walkthroughs and background.

At a glance

Install	pip install hart-sim (Python 3.10+, only dependency PyYAML)
Transport	HART-IP version 1 over TCP and UDP, port 5094; control channel on 5095
Commands	HART revision 7 universal and common practice: 0-3, 6-9, 11-22, 33-38, 40-42, 44-46, 48, 59
Profiles	pressure, temperature, and your own in YAML
Faults	no_response, delay, busy, comm_error, sensor_failure, saturate, cold_start, more_status, drift, write_protect
Tested on	Linux, Windows, macOS; decoded frames checked with Wireshark
License	MIT

What it is not

The two bundled devices are invented, with a manufacturer ID that deliberately belongs to nobody. Most device-specific HART commands are not public, so hart-sim has no profiles after real products.

The byte layouts come from public sources, not from the paid HART specification. hart-sim is not registered with FieldComm Group and has not been tested against real HART hosts. There is no serial HART, burst mode, device description (DD) or secure connection. If your host disagrees with it, please open an issue.