Debug Probes & UART

The two workflows embedded developers usually evaluate first: driving a debug probe (flash / erase / reset / memory reads / RTT) and streaming UART. Both are fully supported by the crate.

Flashing and memory access

DebugNet drives a J-Link/OpenOCD debug probe through the box’s debug service (port 8765, published on the box host):

let lager = lager::LagerBox::from_env()?;
let debug = lager.debug("debug1");

debug.connect()?;
debug.erase()?;
debug.flash("firmware.hex")?;   // .hex/.elf/.bin inferred from extension
debug.reset(false)?;            // false = run after reset

let head = debug.read_memory(0x0800_0000, 16)?;
println!("vector table: {head:02x?}");

flash_bin(path, address) places a raw binary at an explicit address, and flash_bytes uploads an in-memory image — useful when your test builds firmware variants on the fly. info() and status() report probe and target state.

RTT log streaming

rtt() returns a blocking byte stream implementing std::io::Read, so asserting on target output is plain std I/O:

use std::io::{BufRead, BufReader};

let mut lines = BufReader::new(debug.rtt()?).lines();
assert!(lines.next().transpose()?.unwrap().contains("boot ok"));

Tunneled debug service

If the debug service is reached through an SSH tunnel rather than directly, point the crate at it:

let lager = lager::LagerBox::builder("192.168.1.42")
    .debug_service_url("http://127.0.0.1:8765")
    .build()?;

or set the LAGER_DEBUG_SERVICE_URL environment variable.

Streaming UART

Enable the uart feature:

lager = { package = "lager-net", version = "0.2", features = ["uart"] }

A Uart session streams over the box’s Socket.IO /uart namespace. wait_for accumulates output until a needle appears (bytes after the needle stay buffered for the next read), which makes boot assertions one-liners:

use std::time::Duration;

let mut uart = lager.uart("DUT_CONSOLE")?;

// Reboot the DUT and assert on its boot banner.
debug.reset(false)?;
let banner = uart.wait_for(b"boot ok", Duration::from_secs(10))?;
println!("{}", String::from_utf8_lossy(&banner));

// Talk to the DUT's shell.
uart.write_str("version\r\n")?;
let reply = uart.read(Duration::from_secs(2))?;

uart.stop()?;

The session reports adapter re-enumeration (hub power-cycle, DUT reflash) via last_status() — "reconnecting" / "reconnected" — and keeps streaming across it, so power-cycling tests don’t need to reopen the port.

Getting Started

Guides

Debug Probes & UART

Flashing and memory access

RTT log streaming

Tunneled debug service

Streaming UART

​Flashing and memory access

​RTT log streaming

​Tunneled debug service

​Streaming UART

Flashing and memory access

RTT log streaming

Tunneled debug service

Streaming UART