Coming from Arduino

How the parts of an Arduino sketch map to Frothy words, and which boards work.

Frothy runs on ESP32 and RP2040 boards. This page maps the parts of an Arduino sketch to Frothy. It also shows the largest difference: you change a word while the board runs it.

You program the board in the browser editor , not in the Arduino IDE. Install Frothy on the board once with the browser flasher . Then the editor connects to the board over USB, and it sends your code to the board while the board runs.

Boards

These boards have official Frothy firmware:

ESP32 DevKit V1 and NodeMCU ESP-32S
Seeed Studio XIAO ESP32C3, ESP32C6 and ESP32S3
Seeed Studio XIAO RP2040
Arduino Nano RP2040 Connect

Frothy has no firmware for the Arduino UNO, UNO R4, Nano, Nano Every, Nano 33 IoT or Nano R4. Their chips are not ESP32 or RP2040 chips. The Arduino Nano ESP32 has an ESP32-S3 chip, but it has no official Frothy firmware yet. Boards shows how each board connects.

The pins of these boards use 3.3 V. Do not connect a 5 V signal to a pin.

A Sketch Becomes Words

This Arduino sketch blinks the built-in LED:

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(500);
  digitalWrite(LED_BUILTIN, LOW);
  delay(500);
}

Frothy has no setup and no loop. You send code to the board while it runs, with Run Line in the editor or Enter at a prompt. A definition takes effect at once, and a call runs at once. Here an event calls tick every 500 ms:

to tick [ led.toggle: ]
to blink.start [ every 500 [ tick: ] ]
blink.start:

The prompt stays free while the LED blinks. Define tick again, and the next event runs the new word. You do not upload anything, and the board does not restart:

to tick [ led.on: ]

Stop the event with cancel every 500. Type save to keep your words after a restart. A word named boot runs when the board starts:

to boot [ blink.start: ]
save

The LED words need a board with a built-in LED. On a board without one, $led_builtin is nil and led.on: stops with an error. Use gpio.write: pin, 1 with the pin of your own LED.

Arduino Calls And Frothy Words

A colon calls a word. Arguments follow the colon, separated by commas. A word with no arguments still needs the colon: millis:.

Arduino	Frothy	Note
`pinMode(pin, OUTPUT)`	`gpio.mode: pin, 1`
`pinMode(pin, INPUT)`	`gpio.mode: pin, 0`
`pinMode(pin, INPUT_PULLUP)`	`gpio.mode: pin, 2`
`digitalWrite(pin, HIGH)`	`gpio.write: pin, 1`	`0` for `LOW`
`digitalRead(pin)`	`gpio.read: pin`	`0` or `1`
`analogRead(A0)`	`adc.read: $a0`	`0` to `4095`
`analogWrite(pin, value)`	`h is pwm.open: pin, 1000`, then `pwm.write: h, duty`	duty is `0` to `10000`; for Arduino’s `0` to `255`, use `value * 10000 / 255`
`delay(ms)`	`wait: ms`
`millis()`	`millis:`
`Serial.print("hi")`	`print: "hi"`
`Serial.print(x)`	`print: x`	`x` is an integer
`Serial.println("hi")`	`print: "hi\n"`	outside an event body, `print:` adds no line end
`LED_BUILTIN`	`$led_builtin`	`nil` without an LED
`A0`	`$a0`
`a == b`, `a != b`	`a = b`, `a <> b`
`// note`	`-- note`

pwm.open: gives a handle. Close the channel with pwm.close: h. A saved handle comes back as nil after a restart, so open the channel again in boot.

Numbers

Frothy has integers only. 3.14 is an error. To see a number at the prompt, type it or a name that holds it.

Outside an event body, print: writes an integer with no line end. print.value: writes a label, a colon, an integer and a line end, for example light:512. Neither word makes a Text value, so a loop can print for as long as it runs:

repeat 20 [
  print.value: "light", (adc.read: $a0)
  wait: 200
]

The prompt reads one line at a time. Send a word of several lines from the editor or with frothy send.

What Does Not Carry Over

Most Arduino libraries have no Frothy version. Frothy has built-in words for GPIO, ADC, PWM, I2C and UART. Read the hardware reference before you choose a part.