mJs UART API performance problems

[aifer2007]

I try the mJs UART APIs to receive datas on ESP32 uart port.

Data rate: 46 bytes per 20ms, total 23000 bytes in 10s.

There are some performance problems.

let rxAcc = ""; // to store all the bytes received
let rx_total = 0; // total number of received bytes
// Configure UART at 115200 baud
UART.setConfig(1,{
  baudRate: 115200,
});

UART.setDispatcher(1, function(uartNo, ud) {
  let ra = UART.readAvail(uartNo);
  if (ra > 0) {
    let data = UART.read(uartNo);
    rxAcc += data;
    rx_total += data.length;  
  }
}, null);

// Enable Rx
UART.setRxEnabled(1, true);

UART.write(1,"go");  // signal, a nodejs serialport connected to EPS32 will start 
                        sending data

Timer.set(15000 /* milliseconds */, false /* repeat */, function() {
  print("rxAcc lent: "); // =>13150, some datas are lost by rxAcc += data; !!!
  print(rxAcc.length);
  print("rx_total: ");  // =>23000, all the datas are transfered from C to mJs.
  print(rx_total);
}, null);

Here, rx_total = 23000 means that all the datas are received and transfered to mJs by mongoose os kernel.
And, rxAcc.length = 13510 means some datas are lost when "rxAcc += data" is executed !!!

If I change the data rate to 46 bytes per 40ms , rxAcc.length = 23000 all the time, no bytes are lost.

If I delete the "rxAcc += data" line, no data will be lost at the MAX data rate: 46 bytes per 7ms, about 52500bps. Code is here:

UART.setDispatcher(1, function(uartNo, ud) { let ra = UART.readAvail(uartNo); if (ra > 0) { let data = UART.read(uartNo); // rxAcc += data; rx_total += data.length; } }, null);

I have tried to tune the rx buffer size to 1024/2048, the same result.

My questions are:

1. How can I store datas without losing at data rate: 46 bytes per 20ms?

2. Is 52500bps the TOP speed of mJs UART APIs?

3. Is there some way to improve the performance of mJs UART APIs?

[dimonomid]

@aifer2007 , could you please also share the code which sends the data? So that I can reproduce the issue easily.

[aifer2007]

Yes, thanks.
Nodejs code here:

var SerialPort = require("serialport").SerialPort
var serialPort = new SerialPort("/dev/tty.usbserial-A94JN1PL", {
  baudrate: 115200, autoOpen: false,
});

serialPort.open(function (error) {
  if ( error ) {
    console.log('failed to open: '+error);
  } else {
    console.log('open');
    serialPort.on('data', function(data) {
      console.log('data received: ' + data);
      if(data.indexOf('talkstart')> -1) {
        let vd = "1234567890123456789012345678901234567890123456";
        console.log("data packet len: " + vd.length);
        let pktNum = 0;
        let id = setInterval(function(){
          serialPort.write(vd, function(err, results) {
            if(err) {
              console.log('err ' + err);
            } else {
              pktNum++;
              if(pktNum>499) clearInterval(id);
            }
          });
        }, 20); // 46bytes/20ms, 23000 bytes total
      }
    });

  }
});

[dimonomid]

Honestly, failed to reproduce. I used your scripts, and the only (seemingly unrelated) modification I had to do is the following: since I upload init.js to the device and restart it with the following command:

mos put init.js && mos call Sys.Reboot && mos console

we shouldn't emit go in the beginning of device execution, because that could lead to multiple go being emitted (the first one could be emitted right before device reboot), so node script starts two sequences of data. So I emit go after 2 seconds.

All in all, here are the scripts I use:

init.js on esp32:

// Load Mongoose OS API
load('api_timer.js');
load('api_uart.js');
load('api_sys.js');

let rxAcc = ""; // to store all the bytes received
let rx_total = 0; // total number of received bytes
// Configure UART at 115200 baud
UART.setConfig(1,{
  baudRate: 115200,
});

UART.setDispatcher(1, function(uartNo, ud) {
  let ra = UART.readAvail(uartNo);
  if (ra > 0) {
    let data = UART.read(uartNo);
    rxAcc += data;
    rx_total += data.length;  
    print("len:", data.length, "total:", rx_total);
  }
}, null);

// Enable Rx
UART.setRxEnabled(1, true);

// Start communication after 2 seconds
Timer.set(2000 /* milliseconds */, false /* repeat */, function() {
  // signal, a nodejs serialport connected to EPS32 will start sending data
  UART.write(1,"go");
}, null);

Timer.set(17000 /* milliseconds */, false /* repeat */, function() {
  print("==================");
  print("rxAcc lent:", rxAcc.length, "rx_total:", rx_total);
}, null);

Node.js script:

'use strict';

var SerialPort = require("serialport")
var serialPort = new SerialPort("/dev/ttyUSB1", {
  baudRate: 115200, autoOpen: false,
});

serialPort.open(function (error) {
  if ( error ) {
    console.log('failed to open: '+error);
  } else {
    console.log('open');
    serialPort.on('data', function(data) {
      console.log('data received: ' + data);
      if(data.indexOf('go')> -1) {
        let vd = "1234567890123456789012345678901234567890123456";
        console.log("data packet len: " + vd.length);
        let pktNum = 0;
        let id = setInterval(function(){
          serialPort.write(vd, function(err, results) {
            if(err) {
              console.log('err ' + err);
            } else {
              pktNum++;
              if(pktNum>499) clearInterval(id);
            }
          });
        }, 20); // 46bytes/20ms, 23000 bytes total
      }
    });

  }
});

In the end, device always prints:

================== 
rxAcc lent: 23000 rx_total: 23000

[dimonomid]

Closing this one. If you believe that the issue is still here, feel free to provide more details and reopen.