Project Setup

Eventually, you will want to move away from the REPL and start building up firmware proper. Additionally, as Esprit will work on any ESP32 with at least 8MB of flash, you may want to create your own printed circuit board (PCB) for your project. Esprit provides functionality to support this kind of development. An example skeleton project is setup here as a reference.

REPL

The Esprit REPL must be explicitly included in your project to enable REPL support at runtime. Simply (:require [esprit.repl]) in your project's namespace somewhere. Note: if your project is built with :advanced optimizations, the REPL code will probably be removed.

Live Coding

CLI Tools

To connect to the running REPL using the Clojure CLI tools, simply run the following, replacing the endpoint address with the correct IP.

clj -M -m cljs.main -re esprit -ro '{:endpoint-address "10.0.0.1"}' -r

Additionally, the endpoint address can be provided in a config.edn file in the classpath with the :endpoint-address setting. Then, the connection command would be

clj -M -m cljs.main -re esprit -r

Emacs/CIDER

By leveraging CIDER's piggieback library, we can jack-in to a remote REPL by adding a custom cljs-init form. This can be set in the cider-custom-cljs-repl-init-form variable. This variable must be set to

(do (require 'esprit.repl)
    (cider.piggieback/cljs-repl
     (esprit.repl/repl-env)))

Additionally, CIDER's default printing function must be changed to pr as we don't provide support for cljs.pprint at this time. This is set in the cider-print-fn variable, and must be set to 'pr.

Finally, following cider-jack-in-cljs, the REPL environment is set to custom.

An example .dir-locals.el would then be setup as

((nil
  (cider-custom-cljs-repl-init-form . "(do (require 'esprit.repl)
                                           (cider.piggieback/cljs-repl
                                            (esprit.repl/repl-env)))")
  (cider-default-cljs-repl . custom)
  (cider-print-fn . pr)))

Esprit's REPL environment's endpoint address can be set in config.edn with the :endpoint-address setting. The IP of the running Esprit instance is displayed upon successful connection to WiFi.

Other Editors

Contributions welcome!

Board Configuration

Esprit provides a board customization mechanism that can setup various "board items". These items can be pins and peripherals. See [[esprit.board/board-item]] for the currently supported items.

The board file is simply an EDN file on your classpath, and is configured in config.edn by the :board-file setting. If this is not set, the default Esprit board pin definitions will be configured.

For example, say you create a board configuration named my-board.edn in your classpath with the following contents:

{:my-library.file/my-led
 {:type :output-digital
  :pin "D20"
  :value 0}}

In config.edn (also in your classpath), you would then set

{:board-file "my-board.edn"}

In your project or library, you can then use the esprit.board/items map to access the pre-initialized Espruino objects. For example, in my-library/file.cljs one could now use my-led as:

(def my-led (::my-led esprit.board/items))

Blinkenlights

By default, Esprit supports a few LEDs that provide indications for the different stages of the REPL (Read, Eval, and Print) as well as the connection status. To enable them, in your board.edn file, supply pin definitions for the following keywords:

• :esprit.indicators/read-led
• :esprit.indicators/eval-led
• :esprit.indicators/print-led
• :esprit.indicators/conn-led

The initial value for these LEDs depends on the board's hardware setup, but for the Esprit board with the LEDs in the open-drain configuration (logical low turns the LEDs on), the board.edn file would be set up as follows:

{:esprit.indicators/read-led
 {:type :output-analog
  :pin "D14"
  :value 1}
 :esprit.indicators/eval-led
 {:type :output-analog
  :pin "D33"
  :value 0.2
  :freq 1}
 :esprit.indicators/print-led
 {:type :output-analog
  :pin "D32"
  :value 1}
 :esprit.indicators/conn-led
 {:type :output-analog
  :pin "D13"
  :value 1}}

Of course, if these pins are not provided in the board.edn file, the blinkenlight functionality is disabled.