QUERY · ISSUE

ESP32-C6, ESP32-S3, etc.: MICROPY_HW_ENABLE_UART_REPL should be disabled for boards that have both direct USB and UART connectors

openby bikeNomadopened 2025-07-13updated 2025-08-10

enhancementport-esp32

Description

On many ESP32 boards, there are two USB connectors: one connected directly to the MCU and the other connected via a USB/UART bridge chip.

The default ESP32 build for these boards puts the REPL on both ports, making it impossible to use the USB/UART connector as an independent UART for other purposes.

See discussion at #17633 .

Code Size

No response

Implementation

I hope the MicroPython maintainers or community will implement this feature

Code of Conduct

Yes, I agree

CANDIDATE · PULL REQUEST

esp32: Add MICROPY_HW_ENABLE_UART_REPL and enable on generic S2/S3.

mergedby dpgeorgeopened 2022-04-13updated 2022-04-14

port-esp32

Some S2/S3 modules don't use the native USB interface but instead have an
external USB-UART. To make the GENERIC_S3/S3 firmware work on these boards
the UART REPL is enabled in addition to the native USB CDC REPL.

Fixes issues #8418 and #8524.

Assessment

Q Qwen · high

PR #8531 introduced MICROPY_HW_ENABLE_UART_REPL and enabled it on GENERIC_S2/S3 boards to support modules that lack native USB. Issue #17672 is the inverse problem: on boards that DO have native USB, that same flag causes UART REPL to be enabled on both ports simultaneously, making the UART bridge unavailable for independent use. The PR created the mechanism and the default-on behaviour that the issue now wants to make opt-out per board. The PR does not resolve the query — it is arguably the proximate cause of the problem described.

Suggested action

Leave open. PR #8531 provides useful context (it introduced the flag and set the precedent for board-level configuration). The fix requires adding per-board overrides to disable MICROPY_HW_ENABLE_UART_REPL on boards like ESP32-C6/S3 variants that expose native USB as the primary interface. Reference #8531 in any follow-up PR for historical context.