Rosserial_Arduino : Array of Boolean error message

asked 2014-04-13 23:47:35 -0500

Y2D2 gravatar image

Dear all,

I'm having some trouble with the publishing of an array of boolean coming from an arduino using rosserial. The original idea was the following :

#include <ros.h>
#include <roskeepon/sensorstat.h>

ros::NodeHandle  nh;

roskeepon:: sensorstat buttonState;
ros::Publisher chatter1("buttons", &buttonState);

void setup(){
  buttonState.sensorstat_length = 4; }

void loop(){
  for(int i=0 ; i <4;i++){
     buttonState.sensorstat[i] != buttonState.sensorstat[i]; }
  chatter1.publish( &buttonState);

with sensorstat.msg :

bool[] sensorstat

This should change the value of the boolean. But is doesn't, it just initialize a vector of 4 booleans which stay constant. changing the for loop into the following :

for(int i=0 ; i <4;i++){
  if (buttonState.sensorstat[i]){buttonState.sensorstat[i] = false; }
  else { buttonState.sensorstat[i] = true;}

but this gives following error when I try to make the serial connection :

[ERROR] [WallTime: 1397466438.097662] Unable to sync with device; possible link problem or link software version mismatch such as hydro rosserial_python with groovy Arduino

I tried several things : Like using an array of boolean to go through the loop. Which is later copied to buttonState.sensorstat. Same problem : every thing is good when the value is not changed during the loop, once the value starts changing the same error occurs.

I also tried to use the std_msgs / Int8MultiArray with 1 and 0, but the same problem occurs. everything is fine as long as the value doesn't change.

I searched for several days for a solution, also the web and the ROS forum, but I wasn't successful.

I use Hydro and run Ubuntu 12.04 on an Medion Akoya with kernel 3.2.0-60-generic.

I'm new to ROS and the community so I'm not sure of the question is appropriate...

Anyway : Thanks in advance!


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I never used rosserial but could it be the case that buttonState is the data you read from the arduino and when you try setting a value this value gets written to the arduino? Just create a new variable and write to this and then publish this.

BennyRe gravatar image BennyRe  ( 2014-04-14 03:20:30 -0500 )edit

First of all thank you for your reply : but I tried that too : Setting an global boolean array : button : boolean button[4] = {true, false, false, true}; And changing the for loop : for(int i=0 ; i <4;i++){ button[i] != button[i]; } And then using following for loop (as the boolean array of arduino cannot be copied to the boolean array of the ros message.) : for (int i = 0; i<4; i++){ buttonState.sensorstat[i]= button[i]; } But this gives the same result... Or am I not understanding you correctly?

Y2D2 gravatar image Y2D2  ( 2014-04-14 08:14:43 -0500 )edit

I think you have got basically a fundamental problem with programming: Your first for loop for(int i=0 ; i <4;i++){ button[i] != button[i]; } does NOTHING, because you are comparing one boolean on inequality (which always will be false) and asign the result to nothing.

BennyRe gravatar image BennyRe  ( 2014-04-14 19:51:59 -0500 )edit

Second your programming style is far away from every C++ code style I've ever seen. No you didn't get me right. DO NOT WRITE to buttonState.sensorstat. Try this for (int i = 0; i<4; i++){ button[i] = buttonState.sensorstat[i]; } and then publish the button array.

BennyRe gravatar image BennyRe  ( 2014-04-14 19:54:05 -0500 )edit

Ok I saw what I did wrong with the boolean. it should have been button[i] = !button[i]; Still, the same problem occurs and what you suggest doesn't change the msg sent? it changes the internal variable button? Anyway I found something that works, though I'm puzzled why this works and the other one doesn't : I redeclared buttonState in the loop().

Y2D2 gravatar image Y2D2  ( 2014-04-14 23:51:45 -0500 )edit