platformio/platformio-core

Add "break" support to "pio test" ?

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#5310 opened on Nov 12, 2025

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help wantedunit testing

Description

For STM32 via ST-Link, the RTS and DTR modes to reset an uploaded test app don't work. The documented workaround is to add a 2s startup delay.

To considerably speed things up when running multiple tests, pio test could send a BREAK on the serial port, which does an immediate reset.

Would it be possible to add an option to send a break once connected to the USB serial port?

Contributor guide

Tech stack
python
Domain
clitesting
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
PythonPlatformIOserial communication
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Examine the test command implementation in the PlatformIO CLI, likely under platformio/test/ or similar. Research how serial connections are established and how a BREAK signal can be sent using pyserial. Consider the specific requirements for STM32 devices with ST Link and document the approach. Since the issue has no comments, start by clarifying the expected behavior with maintainers.