send ultrasonic value from arduino to raspberry pi running Node-red

[Stijn]

Hi guys,

new on this forum, and no luck yet finding a solution for my (simple) problem.

Setup: ultrasonic sensor connected to arduino nano sending a serial value via USB to a raspberry running Node-red.

arduino code:

#include <NewPing.h>

#define TRIGGER_PIN  8  // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN     7  // Arduino pin tied to echo pin on the ultrasonic sensor.
#define MAX_DISTANCE 350 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.

int test1 = 123;
double test2 = 456;
float test3 = 789;

void setup() {
  Serial.begin(9600); // Open serial monitor at 115200 baud to see ping results.
}

void loop() {
  delay(5000);                     // Wait 50ms between pings (about 20 pings/sec). 29ms should be the shortest delay between pings.
  Serial.println("Sonar");
  Serial.println(sonar.ping_cm()); // Send ping, get distance in cm and print result (0 = outside set distance range)
  Serial.println("test123");
  Serial.println(test1);
  Serial.println(test2);
  Serial.println(test3);
}

Node red



probably I need to implement some kind of conversion but nu luck so far.
can somebody help me out?

thanks,

Stijn

[Colin Law]

Which bit isn't working? You seem to be getting a value of 4 back if I interpret your code correctly.

Colin

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[Stijn]

the 4 value that is displayed in node-red is not the correct value. The correct value is something like 110 or around that.
while the integer, double and float values are received correctly, the sonar.ping_cm() is not.

when I open the serial monitor this is what I get:

Sonar
108   --> displayed in node red as 4??
test123
123
456.00
789.00

Hope this was more usefull :)

thanks in advance!



Op maandag 1 mei 2017 16:29:43 UTC+2 schreef Colin Law:

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[Colin Law]

I am having difficulty seeing how 108 gets converted to "4".

Perhaps you could try converting the result of sonar.ping_cm() to a string before printing it, unless someone can see what the fundamental problem is.

Colin

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[Stijn]

thanks for your reply,

updated code:

#include <NewPing.h>

#define TRIGGER_PIN  8  // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN     7  // Arduino pin tied to echo pin on the ultrasonic sensor.

#define MAX_DISTANCE 200 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.

int test1 = 0;

void setup() {
  Serial.begin(9600); // Open serial monitor at 115200 baud to see ping results.
}

void loop() {
  delay(5000);                   
 

  test1 = sonar.ping_cm();
  Serial.println(test1);
  String stringone = String(test1);
  String stringtwo = String(test1,DEC);
  Serial.println("test1");
  Serial.println(test1); // Send ping, get distance in cm and print result (0 = outside set distance range)
  Serial.println("stringone");
  Serial.println(stringone);
  Serial.println("stringtwo");
  Serial.println(stringtwo);
 
}


serial monitor arduino connected to pc:

test1
118
stringone
118
stringtwo
118


Node red debug screen on Raspberry pi



no doubt I'm doing something wrong, but I can't figure it out.
Anyone any idea?

Thanks!







Op maandag 1 mei 2017 22:40:33 UTC+2 schreef Colin Law:

[Stijn]

No one able to help me out?

Op maandag 1 mei 2017 23:46:00 UTC+2 schreef Stijn:

[Colin Law]

On 1 May 2017 at 22:46, Stijn <stijn.b...@gmail.com> wrote:

 ...            
 

  test1 = sonar.ping_cm();
  Serial.println(test1);
  String stringone = String(test1);

What happens if you replace this with

String stringone = "118";

Colin

[Stijn]

118 is displayed correctly, both on serial monitor and in node red.

apparantly the sonar.ping value is a "long unsigned int", tried to look up how to convert it but didn't find any working example.

maybe that helps you pointing me in the right direction?

thanks in advance!

Stijn




Op vrijdag 5 mei 2017 23:23:16 UTC+2 schreef Colin Law:

[steve rickus]

From what I've seen in the forums, the Serial.println() function does not handle some of the larger 32/64 bit data types as you would expect.

Since your data range in small (0 - 200 it seems?) the output from the ping function should fit in an int. Have you tried casting it as such?

  test1 = (int) sonar.ping_cm();
  Serial.println(test1);

Of course, this would truncate any decimal precision, but that may not be an issue for this use case. But if the received value is still "4" then there are other issues with the connection, I guess...

[Colin Law]

Their must be a way of converting a long unsigned int to a string.
But this is not a node-red issue of course.

Colin

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[mark hubrich]

I don't understand why it needs to be a string. To get the most use of Node-Red wouldn't number work better? For example the smooth node won't work on string. 

I can post a flow I'm messing with when I get home. It's running on RasPi3 with Arduino Mega hooked to it via usb. Aside from the library routine to get data from sonar, it is pretty straight forward sending lots of sensor data just by serial.print. The easiest way I have found is to...

Serial.print(var1);
Serial.print(", ");
Serial.print(var2);
Serial.print(", ");
Serial.print(var3);
Serial.print(", ");
Serial.println(var4);

In node-red I use the CSV node to name the values. It is way easier than doing it on arduino. 

Mark