| driver number |
|---|
8 |
The low-level debug driver provides tools to diagnose userspace issues that make
normal debugging workflows (e.g. printing to the console) difficult. It allows
libraries to print alert codes and apps to print numeric information using only
the command system call, and is easy to call from handwritten assembly. The
driver is in capsules/src/low_level_debug.rs.
-
Description: command() is used to print alert codes and numbers. The driver does not provide a way for an app to wait for the print to complete. If the app prints too many messages in a row, the driver will print a message indicating it has dropped some debug messages.
-
Description: Existence check.
Argument 1: Unused
Argument 2: Unused
Returns: Success
-
Description: Print a predefined alert code. The available alert codes are listed later in this doc. Predefined alert codes are intended for use in library code, and are defined here to avoid collisions between projects.
Argument 1: Alert code to print
Argument 2: Unused
Returns: Success
-
Description: Print a single number. The number will be printed in hexadecimal. In general, this should only be added temporarily for debugging and should not be called by released library code.
Argument 1: Number to print
Argument 2: Unused
Returns: Success
-
Description: Print two numbers. The numbers will be printed in hexadecimal. Like command 2, this is intended for temporary debugging and should not be called by released library code. If you want to print multiple values, it is often useful to use the first argument to indicate what value is being printed.
Argument 1: First number to print
Argument 2: Second number to print
Returns: Success
The following alert codes are defined for use with the predefined alert code command (#1). As an alternative to this table, the binary in tools/alert_codes may be used to decode the alert codes.
| Alert Code | Description |
|---|---|
| 0x01 | Application panic (e.g. panic!() called in Rust code) |
| 0x02 | A statically-linked app was not installed in the correct location in flash |