View Full Version : Serial Communication without terminal

01-06-2009, 10:50 PM
Hi Everybody,

I'm trying to do an serial communication with the FullDuplexSerialPlus object and processing (java based programming tool -> processing.org). my problem is, that i can receive data from the propellor, but when sending, it's not understood by the prop. i guess it's a syntax problem, but i'm not exactly shure what the FullDuplexSerialPlus is expecting as e.g. an end signal. anybody got an idea, what i could try?


Mike Green
01-06-2009, 11:04 PM
The strings processed by the additional routines in the Extended Full Duplex Serial object are assumed to end with a carriage return (13) character. If you need additional information or help, please attach a copy of your Propeller program to your message. It's difficult to give advice without adequate information about the circumstances.

01-07-2009, 05:04 AM
When debugging serial comms, I first make sure the parameters are correct (Baud rate, word length, parity, stop bits). I also (if possible) use a SLOW baud rate -- think 300 baud. I use a terminal or terminal program on the computer -- HyperTerm usually works. Find a way to show what the Propeller thinks it is getting -- through the TV or a second monitor. Finally, if an o'scope is available, hook it up to the Computer --> Prop. line, and enter capital 'U's. The ASCII value for U is 0x55, which gives a nice square wave so you can check the timing, etc.


01-07-2009, 04:26 PM

thanks or replying! I did check the baud rate and the hyperterminal, and it's all working nice with that. To just simply check the communication out, I made the code as simply as possible:


_clkmode = xtal1 + pll16x ' System clock → 80 MHz
_xinfreq = 5_000_000


Debug : "FullDuplexSerialPlus" ' Display object to use with HyperTerminal

PUB Init

'Configure ctra module.
ctra[30..26] := %00100 ' Set ctra for "NCO single-ended"
ctra[8..0] := 27 ' Set APIN to P27
frqa := 0 ' Don't send a tone yet.
dira[27]~~ ' I/O pin to output
dira[9] := 1

'Start FullDuplexSerialPlus.
Debug.start(31, 30, 0, 9600)
waitcnt(clkfreq * 2 + cnt)


PUB SerialTest | incomming

'dira[9] := 1

incomming := Debug.getDec
Debug.Str(String(10, 13, "I got: "))

So it's simply just replying what it's getting. Exactly the same thing i'm doing with processing. as the FullDuplexSerialPlus is waiting for a signal, processing is just writing in a one second loop, and simply just prints out everything that comes in:

import processing.serial.*;

Serial myPort; // Create object from Serial class
int val; // Data received from the serial port

void setup()
size(200, 200);

String portName = Serial.list();
myPort = new Serial(this, portName, 9600);

void draw()

while (myPort.available() > 0) {
String inBuffer = myPort.readString();
if (inBuffer != null) {

(Don't now if this code helps you as it is kind of specific) As I said both codes are very rudamental, and things are working with the hyperterminal. I guess it's more on the processing side...


01-07-2009, 06:47 PM
I just figured out that it's not the sending, but seems to be the opening of the port...

if i'm just looking if the port is open, like:

if (myPort.available() > 0){

it doesn't do anything at the first time. but, when getting impatient disconnect + connect again i just get just bad things from the chip like:

œ4m”h”œ<m”h”œ4m”h”œ4m”h”œ4m”–h”œ<m”–h”œ4m”–h”œ4m”–h”œ4m”–h”h”–h”œ4m ”–h”œ”–h”œ”–

but constantly - i have to reboot the chip in order to calm it down again...

any idea?

01-07-2009, 07:01 PM
Hello timmsta,

the forum can help if you attach your COMPLETE code to a posting.

best regards


01-07-2009, 07:15 PM

it's still the simple code i posted above. am trying things here and there but basicly it's still the same. and still i can read, but can't write. after while i would get this
" œ4m”h”œ<m”h”œ4m”h”œ4m”h”œ4m”–h”œ<m”–h”œ4m”–h”œ4m”–h”œ4m”–h”h”–h”œ4m ”–h”œ”–h”œ” "
so the complete code is above...


01-07-2009, 08:41 PM
Hi Everybody,

I could solve it somehow, but still one bad thing is remaining. But First the solution (may be it might help sombody):

the problem was a confusion in the protocol between the FullDuplexSerialPlus and processing. I solved it like this:

void draw()
if ( myPort.available() > 0) {
val = myPort.readString(); //reading the serial port

String string = Integer.toString(number); //converting my integer to a string, because when processing is sending an int it wouldn't be understood

myPort.write(string); //sending the number as a string
myPort.write(0); //sending 0 as FullDuplexSerialPlus expects it as a termination signal (didn't look up why it works here as an int)
myPort.write('A'); //instead of the "enter"-Signal is use a capital A as Character, otherwise things didn`t work

But still one thing remains: if i disconnect and connect again the propellor keeps sending lots of confusing signs (mentioned above). Does anybody know whats there wrong?


01-07-2009, 08:43 PM
btw: the disconnecting isn't coded it's just kind of this disable thing in PST.