• HDUART
  • Intermediate
  • 3 min
  • Serial CLI

Recipe · Intermediate · HDUART

How to bridge a half-duplex UART bus

Use HDUART bridge mode when TX and RX share a single wire, such as simple single-wire debug buses.

UART signal lines between two connected devices.
A practical ESP32 Bit Pirate workflow based on the documented firmware commands.

Wiring View

BP Shared UART dataHDUART pinGNDGND
Generated from the wiring summary: to BP.
Step 1

Commands

Run the workflow from the CLI after selecting the matching mode.

Result

What it means

The output confirms that the protocol path is working and gives you a baseline for deeper experiments.

Troubleshooting

  • Check baud rate, parity and inversion in config.
  • Avoid driving the line while the target is actively transmitting.
  • Try bytecode for controlled request/response timing.

Next steps

  • Send a short HDUART bytecode query.
  • Document baud rate and inversion.
  • Move repeated exchanges into a script.

Half-duplex UART bridge FAQ

When should I use HDUART instead of UART?

Use HDUART when transmit and receive share one data wire. Standard UART mode expects separate TX and RX lines, so it is the wrong model for single-wire serial buses.

Why are collisions a problem in HDUART bridge mode?

Because Bit Pirate and the target share the same line. If both drive the wire at the same time, bytes can be corrupted and the electrical state can become unsafe for the target.

When is bytecode better than bridge?

Use bytecode when the bus expects a precise request, delay and response length. Bridge mode is convenient for manual exploration, but bytecode gives repeatable timing.

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