Feat/add uart support

[Dzarda7]

Description

This PR adds support for UART reception and processing of SLIP command. It was tested and works on the following targets:

esp32 v3.1
esp32c2 v2.0 (v1.0 does not work!)
esp32c3 v1.0
esp32c6 v0.1
esp32h2 v0.1
esp32s3 v0.2
esp32s2 v1.0
esp32c5 v1.0 and v1.1
esp32p4 v1.2 (need new target for >=v3.0)

Along the way, other stuff was fixed and resolved to enable this like not linking standard libraries which caused build with warnings for newer targets. Erase of bss section and account for checksum in SLIP header.

Related

Related esp-stub-lib PR, not merged yet, needs some modifications: espressif/esp-stub-lib#30

Testing

Tested on mentioned targets using esptool flash-id command. Works, some targets fail because flash chip is not attached, but stub responds correctly.

Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

[github-actions]

	Messages
📖	You might consider squashing your 4 commits (simplifying branch history).

👋 Hello Dzarda7, we appreciate your contribution to this project!

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[Dzarda7]

@dobairoland @radimkarnis @jedi7 This is working implementation for UART. I do not expect many changes in the API on esp-stub-lib side, but it waits for merging as some things needs to be decided. But this can be used for testing. Also review can be done I believe.

[Copilot]

Pull Request Overview

This PR implements UART reception and SLIP protocol command processing for ESP stub firmware, enabling the stub to receive and decode commands from the host. Key changes include implementing the SLIP decoder state machine with buffer management, adding UART interrupt handling, and fixing BSS initialization and checksum handling issues.

Key changes:

• Implements complete SLIP frame reception with state machine, error handling, and buffer management
• Adds UART interrupt handler to receive bytes and process them through SLIP decoder
• Fixes command handler to account for checksum field in SLIP header and replaces inline register functions with macros

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/slip.h	Adds function declarations for frame reception status checking and data retrieval
src/slip.c	Implements SLIP decoder state machine with buffering, error detection, and frame completion tracking
src/main.c	Adds BSS initialization, UART setup with interrupt handler, and main loop for processing received frames
src/command_handler.c	Replaces inline register access functions with macros and accounts for checksum in SLIP header parsing
src/CMakeLists.txt	Adds command_handler.c to build sources
esp-stub-lib	Updates submodule to version with UART support

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[dobairoland]

LGTM in general. Thanks!

[radimkarnis]

Nice job, this LGTM, thank you!

[Dzarda7]

@dobairoland @radimkarnis @jedi7 I believe this should be ready, incorporates all the new changes from esp-stub-lib. I addressed all the suggestions. If you agree, I will merge this.

[dobairoland]

LGTM

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

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