Support boards that auto-reset on serial open (DTR->RST), e.g. STM32W…#27
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Support boards that auto-reset on serial open (DTR->RST), e.g. STM32W…#27Surfbee3 wants to merge 1 commit into
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…L/Wio-E5
Some boards (e.g. Seeed Wio-E5 / STM32WL on a USB-UART bridge) wire DTR -> RST
through a cap, so opening the serial port asserts DTR and resets the MCU. The
connection then fires its handshake (deviceQuery) immediately and races the boot
(~1.2-1.9 s measured), so the query is lost and the connection times out. These
boards currently cannot connect to the web app / CLI at all.
This makes the client tolerate the open-time reset:
- De-assert DTR/RTS right after open() so the line sits steady (Chrome's Web
Serial and Node serialport assert DTR on open). Wrapped in try/catch; a no-op on
boards that don't wire DTR to reset, and setting both low is the run-normally
state for ESP-style auto-reset circuits (won't trigger the bootloader).
- Add an optional bootDelayMs to wait for boot before handshaking. Default 0, so
behaviour is unchanged for native-USB boards. Reset-on-open boards pass e.g. 2500.
Web: WebSerialConnection.open({ bootDelayMs: 2500 })
Node: new NodeJSSerialConnection(path, 2500)
Verified on a Seeed Wio-E5 (STM32WL) companion: getSelfInfo() round-trips with
bootDelayMs=2500 where it previously timed out.
Note for app integrators: if you pass bootDelayMs, size your overall connection
timeout >= bootDelayMs + handshake (the library handshake has no internal timeout).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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…L/Wio-E5
Some boards (e.g. Seeed Wio-E5 / STM32WL on a USB-UART bridge) wire DTR -> RST through a cap, so opening the serial port asserts DTR and resets the MCU. The connection then fires its handshake (deviceQuery) immediately and races the boot (~1.2-1.9 s measured), so the query is lost and the connection times out. These boards currently cannot connect to the web app / CLI at all.
This makes the client tolerate the open-time reset:
De-assert DTR/RTS right after open() so the line sits steady (Chrome's Web Serial and Node serialport assert DTR on open). Wrapped in try/catch; a no-op on boards that don't wire DTR to reset, and setting both low is the run-normally state for ESP-style auto-reset circuits (won't trigger the bootloader).
Add an optional bootDelayMs to wait for boot before handshaking. Default 0, so behaviour is unchanged for native-USB boards. Reset-on-open boards pass e.g. 2500.
Web: WebSerialConnection.open({ bootDelayMs: 2500 })
Node: new NodeJSSerialConnection(path, 2500)
Verified on a Seeed Wio-E5 (STM32WL) companion: getSelfInfo() round-trips with bootDelayMs=2500 where it previously timed out.
Note for app integrators: if you pass bootDelayMs, size your overall connection timeout >= bootDelayMs + handshake (the library handshake has no internal timeout).