README.md

REPL

A simple demo application that provides a bare-bones REPL framework.

Copying This Demo to a New App

1. Copy this demo application, and rename the relevant structures in its Cargo.toml and main.rs.
2. Add it to the Workspace default-members and members arrays by editing ./Cargo.toml
3. Edit the manifest.json file as documented in its README
4. Build using cargo xtask app-image you_new_app to create a flashable Xous image with your app in it.

Details

repl is a baseline demo application for Xous. It uses a chat-client style interface (stacking bubbles of text, with user input right-aligned and shell feedback left-aligned) to facilitate interactions.

It implements the basic envisioned structure of a Xous application, namely:

• Text input comes via the ime-frontend
• Graphical output is rendered via the gam

Push Events and Listeners provides an overview of the flow of messages between an Xous application and the Xous Services.

The one demo command provisioned in the repl app plays a tone via the codec service. This was chosen because it is about one of the most complicated and comprehensive things you can do in the repl environment, as it requires real-time callbacks to fill the audio buffer with new samples. If you have specific questions about how the callbacks work, we encourage you to open an issue in this repo and ask your question. Your questions will help us direct effort toward building the documentation base.

To make your own command, copy the audio.rs template in the apps/repl/src/cmds/ directory, or use this very basic echo template:

use crate::{ShellCmdApi, CommonEnv};
use String;

#[derive(Debug)]
pub struct Echo {
}

impl<'a> ShellCmdApi<'a> for Echo {
    cmd_api!(echo); // inserts boilerplate for command API

    fn process(&mut self, args: String, _env: &mut CommonEnv) -> Result<Option<String>, xous::Error> {
        Ok(Some(rest))
    }
}

The "verb" is the name of your command, and it is the argument to the cmd_api!() macro.

process() is your "main" function, and args is a string which contains the rest of the line that was typed into the chat, minus the verb used to identify your command (e.g. the arguments, but not tokenized or parsed in any way). env contains some items in a common environment, for example, connections to the GAM, LLIO server or other resources required by your implementation.

Once you've added your command to the directory, go to the cmds.rs file, and follow the four-step instructions embedded within the file, starting around line 40.