UART

Open a streaming session against a serial port on the box and drive your DUT’s console from a test.

Enabling the feature

UART sessions ride on Socket.IO, so they are behind a cargo feature:

[dev-dependencies]
lager = { package = "lager-net", version = "0.8", features = ["uart"] }

The uart feature implies blocking. There is no async equivalent.

Handle

use lager::LagerBox;

let lager = LagerBox::from_env()?;
let mut uart = lager.uart("uart1")?;

uart() is the only handle constructor that returns a Result. Every other net handle is inert until you call a method. uart() connects the session and starts streaming immediately, so it can fail right here.

Methods

Method	Description
`netname()`	The net this session streams
`device_path()`	The device path on the box, e.g. `/dev/ttyUSB0`
`baudrate()`	The baud rate the port was opened at
`last_status()`	Most recent session status notification
`read()`	Bytes arriving within a timeout; may be empty
`try_read()`	Bytes already buffered, without waiting
`wait_for()`	Accumulate until a needle appears
`write()`	Write raw bytes to the device
`write_str()`	Write a string to the device
`stop()`	Stop cleanly, closing the port on the box

Method Reference

`read(timeout: Duration) -> Result<Vec<u8>>`

Bytes arriving within timeout. The call can return an empty vector.

read() waits out the full timeout when the device is idle. Use try_read() in a poll loop, or every iteration costs the whole timeout.

`try_read() -> Result<Vec<u8>>`

Bytes already received, without waiting.

`wait_for(needle: &[u8], timeout: Duration) -> Result<Vec<u8>>`

Accumulate until needle appears. Returns: everything up to and including the needle; the remainder stays buffered. An empty needle returns immediately; a miss is Error::Timeout.

`write(data: &[u8]) -> Result<()>` and `write_str(s: &str) -> Result<()>`

Write to the device.

`last_status() -> Option<&str>`

The most recent session status notification, updated during reads. While a USB serial adapter re-enumerates — because a hub port was cycled, or the DUT was reflashed — this reads "reconnecting" and then "reconnected". Checking it distinguishes “the DUT is quiet” from “the adapter went away”.

`stop() -> Result<()>`

Stop cleanly and close the port on the box. Consumes the session. Dropping it also stops the session, but stop() surfaces errors.

Examples

use lager::LagerBox;
use std::time::Duration;

let lager = LagerBox::from_env()?;
let supply = lager.supply("supply1");
let mut uart = lager.uart("uart1")?;

supply.set_voltage(3.3)?;
supply.enable()?;

uart.wait_for(b"boot complete", Duration::from_secs(10))?;
uart.write_str("status\r\n")?;
let reply = uart.wait_for(b"OK", Duration::from_secs(2))?;
println!("{}", String::from_utf8_lossy(&reply));

uart.stop()?;
supply.disable()?;

Survive a reflash without losing the session

use std::time::Duration;

dbg.flash_bin("target/app.bin", 0x0)?;   // the adapter may re-enumerate

// The session reconnects on its own; watch the status while it does.
let banner = uart.wait_for(b"ready", Duration::from_secs(30))?;
println!("status during reflash: {:?}", uart.last_status());
assert!(String::from_utf8_lossy(&banner).contains("ready"));

Supported Hardware

Adapter	Notes
SiLabs CP210x
FTDI FT232R / FT232H / FT2232H / FT4232H	On multi-channel parts, all four channels can serve UART
Prolific USB serial
ESP32 JTAG/serial

Notes

The box owns the port exclusively, and only one session per net or device is allowed. A second opener gets Error::Stream saying the port is already in use. That includes a session your own previous test leaked — call stop().
The connect confirmation timeout is 15 seconds; failing it is Error::Timeout.
Bytes are raw. There is no line discipline, no echo handling and no encoding conversion; wait_for works on bytes.
Sessions carry the gateway bearer token on the Socket.IO handshake, so a gated box needs no extra setup.
On FTDI multi-channel parts, UART works on all four channels, unlike the MPSSE protocols (debug, spi, i2c) which are limited to channels A and B. On a single-channel FT232H, claiming UART makes the MPSSE roles unavailable and vice versa.

Getting Started

Development

Power & Simulation

Measurement

I/O & Communication

Utilities

Security

Guides

Enabling the feature

Handle

Methods

Method Reference

`read(timeout: Duration) -> Result<Vec<u8>>`

`try_read() -> Result<Vec<u8>>`

`wait_for(needle: &[u8], timeout: Duration) -> Result<Vec<u8>>`

`write(data: &[u8]) -> Result<()>` and `write_str(s: &str) -> Result<()>`

`last_status() -> Option<&str>`

`stop() -> Result<()>`

Examples

Wait for a boot banner, then drive the console

Survive a reflash without losing the session

Supported Hardware

Notes

​Enabling the feature

​Handle

​Methods

​Method Reference

​read(timeout: Duration) -> Result<Vec<u8>>

​try_read() -> Result<Vec<u8>>

​wait_for(needle: &[u8], timeout: Duration) -> Result<Vec<u8>>

​write(data: &[u8]) -> Result<()> and write_str(s: &str) -> Result<()>

​last_status() -> Option<&str>

​stop() -> Result<()>

​Examples

​Wait for a boot banner, then drive the console

​Survive a reflash without losing the session

​Supported Hardware

​Notes

Enabling the feature

Handle

Methods

Method Reference

`read(timeout: Duration) -> Result<Vec<u8>>`

`try_read() -> Result<Vec<u8>>`

`wait_for(needle: &[u8], timeout: Duration) -> Result<Vec<u8>>`

`write(data: &[u8]) -> Result<()>` and `write_str(s: &str) -> Result<()>`

`last_status() -> Option<&str>`

`stop() -> Result<()>`

Examples

Wait for a boot banner, then drive the console

Survive a reflash without losing the session

Supported Hardware

Notes