a command line tool for espruino, and esp32 that enables an exellent Developer Experience for these micro-controllers (and others) by:
Last updated a year ago by mkralla11 .
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$ cnpm install espruino-iot-manager 
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Espruino IoT Manager

a command line tool for espruino, and esp32 that enables an exellent Developer Experience for these micro-controllers (and others) by:

  • First, creating and uploading a tiny custom .bootcde file which utilizes the fileList of filenames to load your app modules from Flash in the correct order, which saves an exponential amount of ram allowing more jsVars for your app code. (see Practical / Real-world Memory-savings and Flash Totals section below)
  • watching your IoT app code for changes
  • automatically transpiling app modules (via babel) from es6 after a code change
  • automatically uglifing / minifing (via uglify-js) your app code to it's smallest size
  • converting filenames to storage-appropriate content-hashed names on the device
  • auto-uploading your transpiled files over-the-air to Flash on the device specified by a url of your choice and the provided app code server.
  • Diff's existing app code module filenames with existing app code filenames from the previous build, in order to only download changed modules to your device. New! (similar to, yet slightly different, than hot-module swapping enabled by tools like Webpack, and auto-reloading like Browserify).


  npm install espruino-iot-manager


  Node >= 10

Also, make sure you flash your device with the appropriate espruino firmware before attempting to load your app code on your device. Instructions for flashing to your specific IoT device can be found at


Given a directory structure of your espruino app like the following:

    domains/                          // your app specific domains / modules, or however 
      createAPSetupFlow/              // you like to structure your apps
    index.js                          // your entry point in src

Over The Air (OTA) Application Code Updates Usage

(Suitable boards: esp32, or espruino board with external flash and wifi) First, to load the OTA client boot code onto the device so you can perform OTA updates, simply attach your device via micro USB to USB (or FTDI/serial to USB) to your laptop run the following command:

  esp-iot init-ota-booter

Next, to start serving your application code over-the-air, start your in-memory complication watch server by running the following command:

  esp-iot ota-server

This will kick off the first transpile, minify, and upload (if needed) of app code, and start a server in order to serve your compiled app code from memory to the device when requested. Finally it sets up a filesystem watcher to run the transpile/minify/upload/cache flow again.

commandline flags include:

  esp-iot init-ota-booter
    --default-wifi-username WIFI_NAME 
                                        // REQUIRED. In order for over-the-air app code update to occur, you must have a wifi connection, so you must provide a default-wifi-username so if your app code never connects to the internet while you are working on your app, you the OTA updates can still be performed seamlessly.

    --default-wifi-password WIFI_PASSWORD 
                                        // REQUIRED. see above for explanation.

    --cdn-url IP_ADDRESS
                                        // default: your local ip. The url that's used to serve your code.

    --cdn-url-port 5858
                                        // default: 5858. The port that's used to serve your code.

    --port /dev/tty.SLAB_USBtoUART           
                                        // default: /dev/tty.SLAB_USBtoUART. The path to the port that your IoT device is connected to. (on the commandline, if you are unsure of your port, run `ls /dev/tty.*` to show available ports to try) 

  esp-iot ota-server
    --port 5858
                                        // default: 5858. The port that the server should run on (should match the above --cdn-url-port using via the init-ota-booter command).

    --src /path/to/src/index.js
                                        // default: `${process.cwd()}/src/index.js`. This should be the filepath to the entry point of your app code.

More Notes

if you are having trouble connecting to your esp8266 (or other IoT device) the length of the USB / FTDI / Serial cable matters. I know this sounds absolutely ridicolus (I thought so too), but when I first got started playing with IoT devices and communicating with them via different cables, I always found that SHORTER CABLES WORKED WELL, while longer USB cables could not consistently keep a connection, which was very, very frustrating. My current micro USB to USB cable is 2 feet and works every time.

Also, each individual module that is imported/required by your app code must be less than or equal to 4KB due to the fact that each module is stored in Flash, and the max block size is 4KB per stored item. Although this may seem like a limitation for this upload/boot/run strategy, it actually coaxes you to think more modularly, implicitly helping you to seperate each of your ideas into well encapsulated modules, and importing them to create your whole idea. Not only that, but by storing and executing each module in Flash, you end up saving RAM, allowing you to have more jsVars in your app code, which is a huge win! The Flash idea is based off of thread, so feel free to skim it for a general understanding (note that some info in the thread is based on older info, like some of the numbers/totals that are used).

Practical / Real-world Memory-savings and Flash Totals

For a more practical sense of how rewarding running your code from Flash is, here are the details of my current espruino modularize app transpiled/minified/uploaded using this command line tool:

Name Details
Board esp32 (no psram)
jsVars 2800
Espruino Firmware v. 2v00.42
My Current Real-world App Code Details
Total modules (OTA booter on device) 14
Total modules (app code) 13
Largest individual module size minified (OTA booter on device) 1.750 KB
Largest individual module size minified (app code) 3.850 KB
Total modules size minified (OTA booter on device) 8.796 KB
Total modules size minified (app code) 15 KB
Total jsVars left after upload 1720

The most impressive aspect of these numbers is the fact that I've uploaded a total of almost 9 KB of OTA booter modules and 15 KB of app modules seperately to Flash, and I'm still left with 1720 of 2800 jsVars. Also, one of my previous upload strategies attempted to concatenate all of my modules and write them directly to the .bootcde file uploaded to the device. This was great until I hit the 12KB file limit when writing to .bootcde, which ended up causing the watchdog timeout to repeatedly cause a reboot of my app. So using my new strategy was a huge win, seeing as I couldn't even run my large app without it.

Wipe out all files including OTA, and boot code to start fresh (esp32)

(you must run esp-iot init-ota-booter again if starting fresh)



Licensed under MIT

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