# Jaguar: Live reloading for your ESP32 Jaguar enables live reloading of [Toit](https://toitlang.org/) code when developing for the [ESP32](https://en.wikipedia.org/wiki/ESP32), a popular microcontroller. Develop, update, and restart your code in less than two seconds via WiFi. Use the really fast development cycle to iterate quickly and learn fast! ## What is it? Jaguar is a small Toit application that runs on your ESP32. It uses the capabilities of the [Toit virtual machine](https://github.com/toitlang/toit) to let you update and restart your ESP32 code written in Toit over WiFi. Change your code in your editor, update it on your device, and restart it all within seconds. No need to flash over serial, reboot your device, or wait for it to reconnect to your network. Watch a short video that shows how you can experience Jaguar on your ESP32 in two minutes:

## How does it work? Jaguar runs a small HTTP server that listens for incoming requests. The requests contain compiled Toit programs that are relocated and installed in flash on the device. Before installing a program, we stop any old version of the program and free the resources it has consumed. The new version of the program gets to start again from `main`. ## Community Use this [invite](https://discord.gg/Q7Y9VQ5nh2) to join our Discord server, and follow the development and get help. We're eager to hear of your experience building with Toit. The Discord chat is publicly accessible through our [Linen](https://linen.dev/d/toit). We also use [GitHub Discussions](https://github.com/toitlang/toit/discussions) to discuss and learn. We follow a [code of conduct](CODE_OF_CONDUCT.md) in all our community interactions. ## How do I use it? ### Download Unless you want to [build Jaguar from source](#building-it-yourself), start by downloading and installing the `jag` binary for your host platform. On macOS, you can use [Homebrew](https://brew.sh/) to manage the installation of `jag`: ``` sh brew install jaguar ``` On Windows 10+ you can use the [Windows package manager](https://docs.microsoft.com/en-us/windows/package-manager/winget/): ``` winget install --id=Toit.Jaguar -e ``` Remember to run `winget upgrade --id=Toit.Jaguar -e` (or simply `winget upgrade`) from time to time to keep Jaguar up to date. For Archlinux you can install the AUR package [jaguar-bin](https://aur.archlinux.org/packages/jaguar-bin): ``` sh yay install jaguar-bin ``` For Debian/Ubuntu based systems, you can download the `.deb` package from the [releases page](https://github.com/toitlang/jaguar/releases) and install it: ``` sh sudo dpkg -i jaguar_*.deb ``` As alternative to these package managers, we also offer precompiled binaries for download: - [Download Jaguar for macOS](https://github.com/toitlang/jaguar/releases/latest/download/jag.dmg) (or as an [archive](https://github.com/toitlang/jaguar/releases/latest/download/jag_macos.zip)) - [Download Jaguar for Windows](https://github.com/toitlang/jaguar/releases/latest/download/jag_installer.exe) (or as an [archive](https://github.com/toitlang/jaguar/releases/latest/download/jag_windows.zip)) - [Download Jaguar for Linux](https://github.com/toitlang/jaguar/releases/latest/download/jag_linux.tgz) (only as an archive) If you download an archive, you should unpack it and put the embedded `jag` or `jag.exe` binary somewhere on your `PATH`. The same applies when you extract the `jag` binary from the macOS `jag.dmg` file. ### Setup associated tools Next step is to let `jag` download and configure the Toit SDK and the associated tools for flashing the Jaguar application onto your ESP32: ``` sh jag setup ``` ### Flashing via serial Now it is time to connect your ESP32 with a serial cable to your computer and put the Jaguar application onto it. Running `jag flash` will ask you for the serial port to use and the WiFi credentials, but be aware that the tooling requires [permission to access your serial port](#permission-to-access-serial-port). ``` sh jag flash ``` If you want to avoid typing the WiFi credentials every time you flash, you can store them in Jaguar's config file with: ``` sh jag config wifi set --wifi-ssid SSID --wifi-password PASSWORD ``` After flashing it is possible to monitor the serial output from the device: ``` sh jag monitor ``` Once the serial output shows that your ESP32 runs the Jaguar application, it will start announcing its presence to the network using UDP broadcast. You can find a device by scanning, but this requires you to be on the same local network as your ESP32: ``` sh jag scan ``` ### Running code via WiFi With the scanning complete, you're ready to run your first Toit program on your Jaguar-enabled ESP32 device. Download [`hello.toit`](https://github.com/toitlang/toit/blob/master/examples/hello.toit) and store it in your file system and then run: ``` sh jag run hello.toit ``` Be aware that you can configure the way your applications run by [providing options](#options-for-jag-run) to `jag run`. Also, Jaguar is fast enough that it is possible to ask Jaguar to keep watching your Toit code on disk and to *live reload* it when it changes. Simply write: ``` sh jag watch hello.toit ``` and edit `hello.toit` or any of the files it depends on in your favorite editor. ### Installing services and drivers Jaguar supports installing named containers that are automatically run when the system boots. They can be used to provide services and implement drivers for peripherals. The services and drivers can be used by applications and as such they form an instrumental part of the extensibility of a Jaguar based system. You can list the currently installed containers on a device through: ``` sh jag container list ``` This results in a list that shows the container image ids and the associated names. ``` $ jag container list 85c64060-ffbd-5e04-a0dd-252d5bbf4a32: print-service 4e9a12bc-7f07-5118-9f04-8ad2bbe476d1: jaguar ``` You install a new, or update an existing, container through: ``` sh jag container install print-service service.toit ``` and you can uninstall said container again using: ``` sh jag container uninstall print-service ``` ### Updating Jaguar via WiFi If you upgrade Jaguar, you will need to update the system software and the Jaguar application on your device. You can do this via WiFi simply by invoking: ``` sh jag firmware update ``` Updating the firmware will uninstall all containers and stop running applications, so those have to be transferred to the device again after the update. # Visual Studio Code The Toit SDK used by Jaguar comes with support for [Visual Studio Code](https://code.visualstudio.com/download). Once installed, you can add the [Toit language extension](https://marketplace.visualstudio.com/items?itemName=toit.toit) and get full language support for Toit, including syntax highlighting, integrated static analysis, and code completions. Jaguar already comes with everything you need, so if you can run `jag` from your `PATH`, the extension will automatically find the Toit SDK downloaded by Jaguar and use that. --- # Options for `jag run` It is possible to provide options for `jag run` that control how your applications behave on your device. This section lists the options and provides an explanation for when they might come in handy. ## Limiting application run time You can control how much time Jaguar gives your application to run through the `-D jag.timeout` setting. It takes a value like `10s`, `5m`, or `1h` to indicate how many seconds, minutes, or hours the app can run before being shut down by Jaguar. ``` sh jag run -D jag.timeout=10s service.toit ``` ## Defines Jaguar supports defining values that can be used in your Toit code. This is done through the `-D` option. Its primary use is to configure Jaguar (see below for temporarily disabling Jaguar), but it can also be used to pass values to your Toit code. All defined values that are available in the `jag.defines` assets, where they are stored as Tison. The `encoding.tison` library has functions to extract these values from the assets. ``` sh jag run -D my-define=499 defines.toit ``` ``` toit // defines.toit import encoding.tison import system.assets main: defines := assets.decode.get "jag.defines" --if-present=: tison.decode it --if-absent=: {:} if defines is not Map: throw "defines are malformed" print defines["my-define"] ``` ## Temporarily disabling Jaguar's WiFi You can disable Jaguar's WiFi while your application runs using `-D jag.wifi=false`. This is useful if Jaguar otherwise interferes with your application. As an example, consider an application that uses the WiFi to setup a software-enabled access point ("Soft AP"). This would normally conflict with Jaguar's use of the WiFi, so your application and Jaguar cannot run at the same time. By temporarily disabling Jaguar, it is possible to test and tinker with the Soft AP based service. ``` sh jag run -D jag.wifi=false softap.toit ``` By default this runs with a 10 seconds timeout to avoid making the device inaccessible by Jaguar. You can configure the timeout by passing a separate `-D jag.timeout` option: ``` sh jag run -D jag.wifi=false -D jag.timeout=5m softap.toit ``` This also works for installed containers. Containers that run with `-D jag.wifi=false` start when the device boots and runs to completion before Jaguar tries to connect to WiFi. This allows them to control the WiFi and to prevent Jaguar from taking over before they are ready for it: ``` sh jag container install -D jag.wifi=false softap softap.toit ``` You can also set the timeout for them to make sure they cannot block enabling Jaguar forever: ``` sh jag container install -D jag.wifi=false -D jag.timeout=20s softap softap.toit ``` --- # Permission to access serial port To flash you will need to access the device `/dev/ttyUSB0`. On Linux that means you probably need to be a member of some group, normally either `uucp` or `dialout`. To see which groups you are a member of and which group owns the device, plug in an ESP32 to the USB port and try: ``` sh groups ls -g /dev/ttyUSB0 ``` If you lack a group membership, you can add it with ``` sh sudo usermod -aG dialout $USER ``` You will have to log out and log back in for this to take effect. You can also try `newgrp dialout` to avoid the need to log out and log back in. # Installing via Go You can also install using `go install`. First you'll need to have a [Go development environment](https://go.dev) properly set up (1.16+) and remember to add `$HOME/go/bin` or `%USERPROFILE%\go\bin` to your `PATH`. Using that you can install the `jag` command line tool through: ``` sh go install github.com/toitlang/jaguar/cmd/jag@latest ``` # Building it yourself You've read this far and you want to know how to build Jaguar and the underlying Toit language implementation yourself? Great! You will need to follow the instructions for [building Toit](https://github.com/toitlang/toit) and make sure you can flash a [simple example](https://github.com/toitlang/toit/blob/master/examples/hello.toit) onto your device. We assume all the commands are executed from this directory (the checkout of the Jaguar repository). Start by setting the `JAG_TOIT_REPO_PATH`. Typically, this would be the path to the third_party directory: ``` sh export JAG_TOIT_REPO_PATH=$PWD/third_party/toit ``` Alternatively, `JAG_TOIT_REPO_PATH` could point to a different checkout of Toit. Setup the ESP-IDF environment variables and PATHs, which will allow to compile ESP32 programs. The easiest is to just use the `export.sh` that comes with the ESP-IDF repository: ``` sh source $JAG_TOIT_REPO_PATH/third_party/esp-idf/export.sh ``` Note that Toit's ESP-IDF is patched. Don't use use a plain ESP-IDF checkout instead. Compile everything. ``` sh make ``` This will build the SDK from the `JAG_TOIT_REPO_PATH`, then use it to download the Toit dependencies (using `toit.pkg`) and finally build Jaguar; both the host executable, as well as the Toit program that runs on the device. You can now use Jaguar as usual: ``` sh build/jag flash sleep 3 # Give the device time to connect to the WiFi. build/jag scan # Select the new device. build/jag run $JAG_TOIT_REPO_PATH/examples/hello.toit build/jag monitor ``` ## Contributing We welcome and value your [open source contributions](CONTRIBUTING.md) to Jaguar.