Serial.write() fails on the number 3 (!)

Development Suggestions for the Arduino Project
1

Hi,

I am pretty sure I've found a serious bug in the Serial library - for some reason it writes some numbers but not others. In particular, whenever you try to write the number 3, nothing is sent, but other numbers like 0,1,2, and 4 get sent ok. hex 13 is also sent ok, so it's not just down to certain bits being set. I know this is bizarre but I have done a pretty conclusive test and it looks like this is what's happening.

This code works (prints alternating 0x04's and 0x83's):

void setup() {
  Serial.begin(19200);
}

void loop() {
  unsigned int valOut;  // print out the results from a strike
  unsigned char cOut;
  cOut=0x04;
  Serial.write(cOut);
  cOut=0x83;
  Serial.write(cOut);
  delay(random(MINDEL,MAXDEL));
}

But this doesn't:

void setup() {
  Serial.begin(19200);
}

void loop() {
  unsigned int valOut;  // print out the results from a strike
  unsigned char cOut;
  cOut=0x03;
  Serial.write(cOut);
  cOut=0x83;
  Serial.write(cOut);
  delay(random(MINDEL,MAXDEL));
}

It just prints a series of 83 characters with no 03's at all:

00000000  83 83 83 83 83 83 83 83  83 83 83 83 83 83 83 83  |................|
00000010  83 83 83 83 83 83 83 83  83 83 83 83 83 83 83 83  |................|
00000020  83 83 83 83 83 83 83 83  83 83 83 83 83 83 83 83  |................|
00000030  83 83 83 83 83 83 83 83  83 83 83 83 83 83 83 83  |................|

I'm using arduino version 0022. Could someone verify this on another board and post here so I know my arduino isn't at fault?

2

MINDEL,MAXDEL not defined ...

which program do you use to capture the serial stream on the PC ?

3

The MINDEL MAXDEL bit was my cut and paste error in copying the code. They are both defined as 250.

I got a reply in my original thread pointing out that 0x03 is ctrl-C, so the problem may be caused by the way the serial port is set up, not the arduino library. Sorry about this.

My stty settings are:

andy@monkey:~/Desktop/projects/drum/software/midimapper$ stty -aF /dev/ttyUSB0
speed 19200 baud; rows 0; columns 0; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^A; eol = <undef>;
eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-parenb -parodd cs8 -hupcl -cstopb cread clocal -crtscts
-ignbrk -brkint -ignpar -parmrk inpck -istrip -inlcr -igncr icrnl -ixon -ixoff
-iuclc -ixany -imaxbel -iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig -icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt
echoctl echoke

If anyone knows how they should be set for sending raw data, that would be a help; otherwise I'll do some research and try to work through it myself.

andy

4

Try:

stty -F /dev/ttyUSB0 raw

--
The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons

5

Thanks - I just tried this and it's working fine. Sorry for the false alarm!

6