Switch to synchronous I/O (for GPIO and I2C)

[sandeepmistry]

Might help with #15 and #17 - needs testing.

Can be tested via: npm install sandeepmistry/node-chip-io#sync-io

cc/ @nkolban @rwaldron @ugate @sumarouno @ericterpstra

[nalakawula]

Hi @sandeepmistry , thanks you for mentioning me. I have tried your PR. npm install sandeepmistry/node-chip-io#sync-io

And then, try previous code #15 and try some code for my lcd 1602 with pcf8374T i2c backpack. Here the code I have tried:

lcd_hello_world.js:

"use strict";

var five = require('johnny-five');
var chipio = require('chip-io');

var board = new five.Board({
    io: new chipio()
});

board.on('ready', function() {
    let lcd = new five.LCD({
        controller: "PCF8574A", 
        address: 0x27, 
        bus: 2
    });
    lcd.cursor(0,0);
    lcd.print("Hello World");
    lcd.cursor(1,0);
    lcd.print("1234567890");
    console.log("Percobaan hello world!");
});

lcd_custom_char.js:

var five = require("johnny-five");
var chipio = require('chip-io');

var board = new five.Board({
  io: new chipio()
});

board.on("ready", function() {
  var l = new five.LCD({
        controller: "PCF8574T",
        address: 0x27,
        bus: 2,
        rows: 2,
        cols: 16
  });
    l.useChar("heart");
    l.cursor(0, 0).print("hello, I :heart: JS");
    l.cursor(1, 0).print("NodeJs is great");

});

lcd_runner.js:

var five = require("johnny-five");
var chipio = require('chip-io');

var board = new five.Board({
    io: new chipio()
});

board.on("ready", function() {
    var mylcd = new five.LCD({
        controller: "PCF8574T",
            address: 0x27,
            bus: 2,
            rows: 2,
            cols: 16
    });

    var frame = 1;
    var frames = [":runninga:", ":runningb:"];
    var row = 0;
    var col = 0;

    mylcd.useChar("runninga");
    mylcd.useChar("runningb");

    this.loop(300, function() {
        mylcd.clear().cursor(row, col).print( frames[frame ^= 1] );
        if (++col === mylcd.cols) {
            col = 0;
            if (++row === mylcd.rows) {
                row = 0;
            }
        }
    });
    console.log("percobaan running");

});

All above code work well after using sync-io. Run the code, stop the code, run again, stop again. And no more garbage text as discussed #15 . I can confirm, no more garbage text again in my lcd. Your work is great, thank you very much.

[sandeepmistry]

@sumarouno excellent thanks for trying out the changes!

I'll hold off merging for a week or so, so most testing can be done.

[nalakawula]

I will try more code as soon as possible. Fyi, this PR still not solve for #17

[rwaldron]

• Reading needs to be async
• Writing can be async, but only if order can be guaranteed and there is no dependency on a callback before the next operation. On systems that have no way of doing async writes, a sync write can often be faster and more efficient.
  • Realistically an async write doesn't make any difference when the program cares primarily about order of received writes. Async writing is useful for web application servers that must do writing and responding to some HTTP request as efficiently and non-blocking as possible. Sync writes for robots are generally no more than a byte and frequently less than 32 bytes—which is trivial and unlikely to cause any substantial IO blocking for sensors being read.
  • When implementing write operations, it's important to remember that we're trying to model as closely as possible to a serialport.write(), which is a write queue over a wire. The write is queued in the same turn, but the callback is called in the following turn—but that's meaningless for our purposes.

[sandeepmistry]

@rwaldron thanks for reviewing and providing your feedback. I think everything is up to spec now.

[rwaldron]

@sandeepmistry you're the best!