ESP8266 UART question

[espruino-discuss]

Posted at 2020-06-16 by user106712

From http://www.espruino.com/USART

"As software serial doesn't use dedicated hardware there are some compromises:

Baud rates significantly above 9600 baud are unlikely to be reliable
Sending more than one or two characters will block execution of other JavaScript code until completion (hardware serial ports have a ~100 byte transmit buffer)
Software serial reception will become increasingly unreliable the higher the CPU load."

In my application, I use soft serial (rx=D5, tx=D6). I get bursts of 60+ bytes (5x a second) from an external source. I find that anything beyond 2400 baud increases errors in the data received. What's the experience of others?

Using an Amica 8266 board.

[espruino-discuss]

Posted at 2020-06-17 by @MaBecker

do you like to share your serial code section so others cant test and recommend some optimisation if needeed.

have you tried to connect over tcp/ip and use the hardware serial for communication?

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Posted at 2020-06-17 by user106712

I am using two soft serials, taking input from one UART and passing it to the USB UART.

var hubSerial = new Serial(); 
	hubSerial.setup(2400, { // problematic when baud rate=9600
		rx: NodeMCU.D5,
		tx: NodeMCU.D6
	});
    var usbSerial = new Serial(); 
	usbSerial.setup(9600, {
		rx: NodeMCU.D9,
		tx: NodeMCU.D10
	});

	usbSerial.on('data', function (data) {
		try {
			hubSerial.print(data);
		} catch (e) {
			d0("failed to send on hub's data");
		}
	});
	hubSerial.on('data', function (data) {
		try {
			usbSerial.print(data);
		} catch (e) {
			d0("failed to send on usb's data");
		}
	});

d0() is essentially console.log over port 23.

The PIN assignment cannot be changed hence the use of soft serial. I think the issue is that .on('data',..) is coming back 1 or 2 bytes at a time. I will experiment using .available().

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Posted at 2020-06-17 by user106712

Using hubSerial.available() - rather than hubSerial.data('on') - to chunk the input stream seems to make some difference (fewer errors) at 4800 baud. But no difference at 2400 (mostly good) or 9600 (bad transmission). See code below (both .available and .on('data') fragments are included:

var d0 = console.log;
var debug = console.log;

var hubSerial = new Serial();
var usbSerial = new Serial();

function onInit() {
	hubSerial.setup(4800, { // problematic when baud rate=9600
		rx: NodeMCU.D5,
		tx: NodeMCU.D6
	});
	usbSerial.setup(9600, {
		rx: NodeMCU.D9,
		tx: NodeMCU.D10
	});

    usbSerial.on('data', function (data) {
        try {
            hubSerial.print(data);
        } catch (e) {
            d0("failed to send on hub's data");
        }
    });
  
    //*
	hubSerial.on('framing', function (data) {
		d0("framing error");
	});
	
	setInterval(() => {
		let n = hubSerial.available();
		if (n > 0) {
			//d0(n);
			let d = hubSerial.read(0);
			usbSerial.print(d);
		}
	}, 200);
    //*/

	/*
	hubSerial.on('data', function (data) {
		try {
         // d0(data.length);
			usbSerial.print(data);
		} catch (e) {
			d0("failed to send on usb's data");
		}
	});
	//*/
}

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Posted at 2020-06-19 by @MaBecker

If you like you can run some tests with removing TX if you just reading and RX if just sending.