1.1 KiB
Viewing Logs
To observe the program logs you can use the cargo-embed tool.
$ cargo embed --bin hello
This command will bring up a Text User Interface (TUI). You should see "Hello, world!" in the output. You can close the interface using Ctrl-C.
cargo-embed has no --chip flag; instead the target chip needs to be specified in a file named Embed.toml. This file must be placed in the root of the Cargo project / workspace, next to the Cargo.toml file.
# Embed.toml
[general]
chip = "nRF52840_xxAA"
Logging is implemented using the Real Time Transfer (RTT) protocol. Under this protocol the target device writes log messages to a ring buffer stored in RAM; the PC communicates with the J-Link to read out log messages from this ring buffer. This logging approach is non-blocking in the sense that the target device does not have to wait for physical IO (USB comm, serial interface, etc.) to complete while logging messages since they are written to memory. It is possible, however, for the target device to overrun the ring buffer; this causes old log messages to be overwritten.