adafruit-mcp23008-ssd1306-node-driver

Node driver for Adafruit MCP23008 and SSD1306

This package is designed to let us talk to this thing using node on a Rasberry Pi running Raspbian.

That is, we can detect button presses and write stuff to the display.

How to install

npm install adafruit-mcp23008-ssd1306-node-driver

How to use it

Try this to run a quick demo. It echos button presses to the display.

const adafruit = require("adafruit-mcp23008-ssd1306-node-driver")
adafruit.demo()

Here's how to do it yourself:

const adafruit = require("adafruit-mcp23008-ssd1306-node-driver")
const ButtonDriver = adafruit.ButtonDriver
const DisplayDriver = adafruit.DisplayDriver
 
const busNumber = 1
 
const displayAddress = 0x3c
const displayDriver = new DisplayDriver(busNumber, displayAddress)
 
const buttonsAddress = 0x20
const buttonDriver = new ButtonDriver(busNumber, buttonsAddress)
 
buttonDriver.watchAllButtons(function(buttonPin) {
  displayDriver.writeText("Clicked button #" + buttonPin)
})
 
displayDriver.writeText("OK, click some buttons")
console.log("Check the display...")

You can also watch just one button:

buttonDriver.watchButton(1, function(buttonPin) {
  console.log("Clicked button #" + buttonPin)
})

You can also display QR codes:

displayDriver.setQrCode("http://www.google.com")

Note that the display driver runs a background loop to keep the display refreshed. So your process won't exit until you call:

displayDriver.stop()

Using tabs

This driver has a "tab" mechanism, using the metaphor of tabs in a web browser. Send the tab name as the last parameter of any method. If you don't specify a tab, it will use "default". Switch the current using displayDriver.showTab(...).

Example:

displayDriver.writeText("First tab", 0, 0, false, "tab1")
displayDriver.writeText("Second tab", 0, 0, false, "tab2")
displayDriver.showTab("tab2")

If you write stuff on a tab that isn't the current tab, then nothing changes on the display until you show that tab. Just like with real tabs.

Testing

If you are in a development environment with no access to the actual screen, you can use the fakes.

const adafruit = require("adafruit-mcp23008-ssd1306-node-driver")
 
console.log("Has driver: ", adafruit.hasDriver())
const fakeDisplayDriver = new adafruit.FakeDisplayDriver()
const fakeButtonDriver = new adafruit.FakeButtonDriver()

• FakeDisplayDriver: has all the same methods as DisplayDriver, but displays on the terminal instead of the SSD1306 display.
• FakeButtonDriver: has all the same methods as ButtonDriver, but you simulate button presses using your keyboard (press 0, 1, or 2).

How it works internally

The button stuff is a node port of this code:

• https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/blob/legacy/Adafruit_MCP230xx/Adafruit_MCP230xx.py
• https://github.com/HWHardsoft/Display_Shield_RPI/blob/master/standard_test.py

For display stuff is a wrapper around:

• https://www.npmjs.com/package/oled-i2c-bus