# Trouble with the Serial port read
**URL:** https://discourse.processing.org/t/trouble-with-the-serial-port-read/10724
**Category:** Electronics (Arduino, etc.)
**Created:** [April 28, 2019, 6:26pm UTC](https://discourse.processing.org/t/trouble-with-the-serial-port-read/10724 "2019-04-28T18:26:55Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@laptophead](https://discourse.processing.org/u/laptophead)
#### Post date: [April 28, 2019, 6:26pm UTC](https://discourse.processing.org/t/trouble-with-the-serial-port-read/10724/1 "2019-04-28T18:26:56Z")
I am getting a periodic string from an Arduino Mega, about once a second.
I parse it and get various values from it.
About every 20 messages I get this weird error, and I dont know why.
Here is my receiving code
```auto
while ( myPort.available() > 0 )
{ // myPort.clear();
IncomingSTR = myPort.readStringUntil('\n'); // read it and store it in val
println (IncomingSTR);
if (IncomingSTR != null)
{
String[] list = split(IncomingSTR, ' ');
MACH_ID= list [0];
PeriodMillis = list [1];
Channel = list [2];
Operator= list [3];
MoreInfo = list [4];
}
```
Here is the read of the String:
```auto
32A 1868 3 NAME INFO ;
43A 1337 3 NAME INFO ;
30A 1800 3 NAME INFO ;
35A 1607 3 NAME INFO ;
37A 1571 3 NAME INFO ;
null
null
null
null
null
null
null
null
null
null
null
null
null
null
null
null
null
null
null
null
null
null
26B 2855 3 NAME INFO ;
34B 1703 3 NAME INFO ;
```
How could I get a “null” 20 times in a row?
When I look at the Arduino output in the Serial Monitor, all strings are nice and clear, no garbage…
I am running this at 112500 baud. I need the speed.
I tried various arduino manufacturers , including the orignal Italian one. THey all do it, but some chinese clones do it less.
At times the Processing Sketch crushes and I get a :ArrayIndexOutOfBoundsException: 3
The Index number varies. (Not always 3)
What hat am I doing wrong?
Thanks
Mitch
---
### Author:  [@kll](https://discourse.processing.org/u/kll)
#### Post date: [April 29, 2019, 1:25am UTC](https://discourse.processing.org/t/trouble-with-the-serial-port-read/10724/2 "2019-04-29T01:25:50Z")
your serial code is based on?
[https://processing.org/reference/libraries/serial/Serial\_readStringUntil\_.html](https://processing.org/reference/libraries/serial/Serial_readStringUntil_.html)
so if you want print the "null"s up to you.
* * *
a arduino might send a CR LF,
so you guess why you have empty lines in your print
pls use a
[https://processing.org/reference/trim\_.html](https://processing.org/reference/trim_.html)
on the instring
* * *
for the rest of the instring work need still much more error checking
-a-
the split will fail if there is no " "
so try a
[https://processing.org/reference/match\_.html](https://processing.org/reference/match_.html)
first
-b-
also first make sure that the array is that long before you use a list[4]
by using
if ( list.length \>=5 ) // …
* * *
generally using the
[https://processing.org/reference/libraries/serial/serialEvent\_.html](https://processing.org/reference/libraries/serial/serialEvent_.html)
is better as a check inside draw()
* * *
---
### Author:  [@laptophead](https://discourse.processing.org/u/laptophead)
#### Post date: [April 29, 2019, 5:46pm UTC](https://discourse.processing.org/t/trouble-with-the-serial-port-read/10724/3 "2019-04-29T17:46:30Z")
Thank you , thank you,
Using Serial Event was fixed all my problems. I tried it on 3 different arduinos and they all work fine.
Here is the code for other folks:
```auto
int lf = 10; // ASCII linefeed
void setup() {
size(400, 200);
printArray(Serial.list());
myPort = new Serial(this, Serial.list()[0], 115200);
myPort.bufferUntil(lf);
}
void draw() {
background(0);
//text("received: " + inString, 10,50);
}
void serialEvent(Serial p) {
String IncomingSTR = p.readString();
println( IncomingSTR);
if (IncomingSTR != null)
{
String[] list = split(IncomingSTR, ' ');
if ( list.length >=5 )
{
MACH_ID= list [0];
PeriodMillis = list [1];
Channel = list [2];
Operator= list [3];
MoreInfo = list [4];
}
}
}
```
---
### Author:  [@kll](https://discourse.processing.org/u/kll)
#### Post date: [April 30, 2019, 6:22am UTC](https://discourse.processing.org/t/trouble-with-the-serial-port-read/10724/4 "2019-04-30T06:22:46Z")
still using trim and match can make it better,
add
```auto
if ( list.length >=5 ) {
MACH_ID= list [0];
PeriodMillis = list [1];
Channel = list [2];
Operator= list [3];
MoreInfo = list [4];
} else println("lost line: "+IncomingSTR);
```
---
### Author:  [@laptophead](https://discourse.processing.org/u/laptophead)
#### Post date: [May 2, 2019, 12:16pm UTC](https://discourse.processing.org/t/trouble-with-the-serial-port-read/10724/5 "2019-05-02T12:16:35Z")
Yes, I implemented that too.
But now I get an error if I start the sketch in the middle of a transmission, or the string is not complete.
Then the sketch does not run.
I get
> 34B 33664 O ;
> 5:12:32
> lost line: 34B 33664 O ;
Error, disabling serialEvent() for COM7
null
I would rather just trash the partial string, and continue receiving.
Any thoughts?
Thanks
Mitch
---
### Author:  [@kll](https://discourse.processing.org/u/kll)
#### Post date: [May 2, 2019, 12:29pm UTC](https://discourse.processing.org/t/trouble-with-the-serial-port-read/10724/6 "2019-05-02T12:29:11Z")
see
[Issue with using array after splitTokens()](https://discourse.processing.org/t/issue-with-using-array-after-splittokens/10826/4) here