Bridge Speed

Official Hardware Classic Yún
1

Hi,

I'm new to the Yun but loving it so far.

I did a quick test controlling a PWM pin via Bridge and added a minimal html page with a range input slider to control it.

It seems to work fine if I make a GET request when releasing the slider, but it's pretty slow when making multiple GET request as I drag the slider. I'm guessing this isn't how this should be done (flooding the Arduino with GET requests).

Is it possible to use Bridge to send continuous/realtime requests to the MCU ? If so, how ?

At the moment I'm thinking I should probably write a Python script that opens a socket and the serial port and does the communication this way. Any other suggestions in this direction ?

Thanks,
George

2

That's how most users have solved the problem: disabling ttyATH0 as linux terminal and use it as pure serial. However, this is hard stuff. Since premature optimization is the root of all evil, I suggest you to postpone this phase until the very last minute.

3

for the record, if you google for things like "yun python tornado" or use SpaceBrew (there is an example with the IDE) you'll get much better performances

4

I agree 100%. Specially count kernel command line flood boot message into ttyATH0 (at first 2 mins booting time) plus afterwards send all error and warning messages to ttyATH0 which make using ttyATH0 without error detection and correction become useless. I recall my professor told me more than 3 decades ago "setup serial communication without error detection and correction just like 'left hand hold gun shoot right hand'"

5

Profile bridge speed:

Arduino Yun Bridge example from IDE.

ab - Apache HTTP server benchmarking tool

http://httpd.apache.org/docs/2.2/programs/ab.html

ab -n 20 -c 1 http://192.168.0.186/arduino/analog/2/123

Concurrency Level:      1
Time taken for tests:   3.425 seconds
Complete requests:      20
Failed requests:        0
Write errors:           0
Non-2xx responses:      20
Total transferred:      2100 bytes
HTML transferred:       0 bytes
Requests per second:    5.84 [#/sec] (mean)
Time per request:       171.275 [ms] (mean)
Time per request:       171.275 [ms] (mean, across all concurrent requests)
Transfer rate:          0.60 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       0
Processing:   164  171   7.9    169     192
Waiting:      153  159   6.2    156     171
Total:        164  171   7.9    169     192

171.275 [ms] (0.17 s) is average speed of bridge speed, and should meet average application's requirement.

6

Hi,

Thank you all for the helpful responses!

I'm afraid I only have more questions at the moment.

@sonnyyu

I've just done a similar test and it generally seems about twice as slow:

ab -n 20 -c 1 http://192.168.240.1/arduino/byte/-1
This is ApacheBench, Version 2.3 <$Revision: 1430300 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 192.168.240.1 (be patient).....done


Server Software:
Server Hostname:        192.168.240.1
Server Port:            80

Document Path:          /arduino/byte/-1
Document Length:        18 bytes

Concurrency Level:      1
Time taken for tests:   6.843 seconds
Complete requests:      20
Failed requests:        0
Write errors:           0
Total transferred:      2380 bytes
HTML transferred:       360 bytes
Requests per second:    2.92 [#/sec] (mean)
Time per request:       342.163 [ms] (mean)
Time per request:       342.163 [ms] (mean, across all concurrent requests)
Transfer rate:          0.34 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        2    3   1.3      3       6
Processing:   228  339  46.5    346     421
Waiting:      211  322  47.4    329     418
Total:        231  342  46.5    348     423

Percentage of the requests served within a certain time (ms)
  50%    348
  66%    351
  75%    376
  80%    390
  90%    397
  95%    423
  98%    423
  99%    423
 100%    423 (longest request)

ab -n 20 -c 1 http://192.168.240.1/arduino/byte/-1
This is ApacheBench, Version 2.3 <$Revision: 1430300 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 192.168.240.1 (be patient).....done


Server Software:
Server Hostname:        192.168.240.1
Server Port:            80

Document Path:          /arduino/byte/-1
Document Length:        18 bytes

Concurrency Level:      1
Time taken for tests:   6.654 seconds
Complete requests:      20
Failed requests:        0
Write errors:           0
Total transferred:      2380 bytes
HTML transferred:       360 bytes
Requests per second:    3.01 [#/sec] (mean)
Time per request:       332.717 [ms] (mean)
Time per request:       332.717 [ms] (mean, across all concurrent requests)
Transfer rate:          0.35 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        1    3   1.6      3       8
Processing:   234  329  46.7    328     452
Waiting:      214  309  48.8    311     430
Total:        239  332  46.3    333     455

Percentage of the requests served within a certain time (ms)
  50%    333
  66%    351
  75%    361
  80%    367
  90%    372
  95%    455
  98%    455
  99%    455
 100%    455 (longest request)

Any hints on what I should do to improve this ?

@Federico Fissore
I installed tornado and tried a sample:

import tornado.ioloop
import tornado.web
import tornado.websocket
import serial
from tornado.options import define, options, parse_command_line
ser = serial.Serial('/dev/ttyATH0', 57600)
define("port", default=8888, help="", type=int)
class WebSocketHandler(tornado.websocket.WebSocketHandler):
    def open(self, *args):
        print "Connected"
    def on_message(self, message):
        dato_1 = str(message)
        print (message)
	ser.write(dato_1)
    def on_close(self):
        print "Disconnected"
app = tornado.web.Application([
    (r'/w/', WebSocketHandler),
])
if __name__ == '__main__':
    parse_command_line()
    app.listen(options.port)
    tornado.ioloop.IOLoop.instance().start()

and a test client:

<!doctype html>
<!--[if lt IE 7]> <html class="no-js ie6 oldie" lang="en"> <![endif]-->
<!--[if IE 7]>    <html class="no-js ie7 oldie" lang="en"> <![endif]-->
<!--[if IE 8]>    <html class="no-js ie8 oldie" lang="en"> <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js" lang="en"> <!--<![endif]-->
<head>
	<meta charset="utf-8">
	<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">

	<title></title>
	<meta name="description" content="">
	<meta name="author" content="">

	<meta name="viewport" content="width=device-width,initial-scale=1">

	</head>
<body>

	<script>
		//ws://192.168.0.9:8888
		//weso://ARDUINO.YUN.IP.ADRESS:8888/w/
		var connection = new WebSocket('ws://192.168.0.9:8888/ws/', ['soap', 'xmpp']);
		
		connection.onopen = function () {
		  connection.send('Ping'); // Send the message 'Ping' to the server
		};

		// Log errors
		connection.onerror = function (error) {
		  console.log('WebSocket Error ' + error);
		};

		// Log messages from the server
		connection.onmessage = function (e) {
		  console.log('Server: ' + e.data);
		};
		
	</script>

</body>
</html>

but I always get a 404:

WebSocket connection to 'ws://192.168.0.9:8888/ws/' failed: Error during WebSocket handshake: Unexpected response code: 404

I've tried ws://192.168.0.9:8888 as well and I can see all these errors on my Yun as well:

root@yun:/www/ws# python ws.py
[W 140923 22:03:22 web:1811] 404 GET / (192.168.0.4) 12.83ms
[W 140923 22:07:42 web:1811] 404 GET /ws/ws.py (192.168.0.4) 10.97ms
[W 140923 22:13:11 web:1811] 404 GET /ws/ (192.168.0.4) 9.35ms

How do people get the example working on a yun ?

Also, regarding Spacebrew, I'm afraid I've tried that before with little success on the Yun so far:
http://forum.spacebrew.cc/t/issues-using-arduino-yun/57

Thank you all again for your contributions.
Looking forward to your responses.

7

I am traveling and not access Yun. But quick peak;-

  1. Base ip you are on wifi, I use wire ethernet.
    2.base on HTML transfer 360 bytes, you did not use bridge sample from IDE.
  2. Use powerful machine run 'ab'
8

sorry George, I don't know Tornado, I was just mentioning some users were successful in using it. You should google for an hint

9

Hi,

Thank your for the suggestions.

@sonnyyu

  1. I am planning to use wifi most of the time, not ethernet.
  2. I started with the Bridge sample from the IDE, but then tried to simplify as much as I could.
    My test code so far looks like this:
#include <Bridge.h>
#include <YunServer.h>
#include <YunClient.h>
#include <SoftwareSerial.h>

const int pwm = 11;
int value = 255;

YunServer server;

void setup() {
  pinMode(pwm,OUTPUT);
  
  Bridge.begin();
  server.begin();
}

void loop() {
  YunClient client = server.accept();
  if (client) {
    process(client);
    client.stop();
  }
  analogWrite(pwm,value);
}
void process(YunClient client) {
  String command = client.readStringUntil('/');
  if (command == "pwm"){
    pwmCommand(client);
  }
}
void pwmCommand(YunClient client){
  int pin, pwmVal;
  pwmVal = client.parseInt();
  pwmVal = constrain(pwmVal,0,255);
  value = pwmVal;
}

and a simple html test:

<!DOCTYPE html>
<html>
<head>
    <title>Arduino REST demo</title>
  <meta name="viewport" content="width=device-width,initial-scale=1.5">
  <script src="../jquery.min.js"></script>
  <script>
    function pwmSet(value){
      console.log(value);
      var url = "/arduino/pwm/"+value+"/";
      $.get(url).done(getCallback);
    }
    function getCallback(data){
      console.log(data);
    }
  </script>
</head>
<body>
  <form>
    <label for="pwm">PWM pin 11</label><input id="pwm" type="range" min="0" max="255" value="255" oninput="pwmSet(pwm.value);">

  </form>
</body>
</html>

Moving the slider results in a queue that moves quite slow. Is there any way to improve this ?

  1. I've run the ab on a machine with a machine with with 4GB of RAM and a core i7 Intel CPU. This should suffice ?

@Federico Fissore

The errors with tornado can be resolved by overriding the check_origin method of the WebSocketHandler subclass

def check_origin(self,origin):
   return True

I can confirm using tornado and pyserial gives me responsive results dimming a PWM LED.

Has anyone had success with Spacebrew on the Yun ?

10

@sonnyyu My guess is even if I go with the Ethernet option it won't be fast enough for something like controlling a PWM LED in realtime (probably because of the large amount of separate request flooding). Can you please confirm if this is the case or not when you get a chance ? With your setup can you control a PWM LED in realtime ? If so how ?

Also, I still haven't managed to get Spacebrew working with the Yun. Has anyone else had any luck with this ?

Thanks,
George

11

If you need more than 5s /second then you need by pass bridge, but Cyclic Redundancy Check (CRC) is needed at both Openwrt and arduino sides.