Serial.readString does not give whole string

ratatosk1 · September 22, 2020, 9:49am

Hi,

I am trying to basically read string from serial. However it readString does not give me whole the Serial1 response.

when the code is:

Serial1.println("AT+CGNSINF");
it gives me this:

AT+CGNSINF

+CGNSINF: 1,1,20200922094421.000,36.208805,36.1558

I tried Serial.readStringUntil('\n'); but still no change unfortunately.

However, when I tried to do this with Serial monitor itself, like writing to command to serial monitor manually it gives me the true answer like:

AT+CGNSINF

+CGNSINF: 1,1,20200922094719.000,36.208752,36.155862,121.200,0.17,229.9,1,,1.0,1.3,0.9,,10,8,,,43,,

OK

Why this is happening? can someone help me?

anon73444976 · September 22, 2020, 9:57am

ratatosk1:
Why this is happening? can someone help me?

Maybe there's something wrong with the code you didn't post.

ratatosk1 · September 22, 2020, 10:02am

So, this is the GPS function

int getGPS()
{

	sendSingleCommand("AT+CGNSINF", 200); //500
  Serial1.flush();
  Serial.flush();
  //delay(500);
  
	while(Serial1.available())
    {
        String tempAns = Serial1.readString();
       // Serial.println(tempAns);

        if(getSplittedValue(tempAns,',', 1).equals("1"))
        {
            String latS = getSplittedValue(tempAns,',',3);
            String longS = getSplittedValue(tempAns,',',4);
            String gnss = getSplittedValue(tempAns,',',15);
            String glonass = getSplittedValue(tempAns,',',16);
            
            latt = latS.toFloat();
            longg = longS.toFloat();
            gnssnum = gnss.toInt();
            glonassnum = glonass.toInt();

            Serial.print("GPS Updated: ");
            Serial.print(latt);
            Serial.print(",");
            Serial.print(longg);
            Serial.print(",");
            Serial.print(gnssnum);
            Serial.print(",");
            Serial.print(glonassnum);
            Serial.println();
            return 1;
        }
        else
        {
            Serial.println("Cannot take GPS Signal");
            return 0;
        }
    }
}

In this function I cant get the number of gnss and glonass satellites seen

AT+CGNSINF

+CGNSINF: 1,1,20200922094719.000,36.208752,36.155862,121.200,0.17,229.9,1,,1.0,1.3,0.9,,10,8,,,43,,

OK

Here these numbers are 10 and 8. Is this indexing fault or something?

Robin2 · September 22, 2020, 11:25am

Serial.readString() has a timeout - maybe that triggers before the full message arrives.

Have a look at the examples in Serial Input Basics - simple reliable non-blocking ways to receive data.

What Arduino board are you using?

Note that Serial.flush() is used when sending data - it makes the Arduino wait until all the data has been sent.

...R

Grumpy_Mike · September 22, 2020, 3:44pm

TheMemberFormerlyKnownAsAWOL:
Maybe there's something wrong with the code you didn't post.

Still not posted it have you?

http://snippets-r-us.com

ratatosk1 · September 22, 2020, 6:37pm

Posted it dont you see

anon73444976 · September 22, 2020, 6:48pm

ratatosk1:
Posted it dont you see

I see a snippet.

ratatosk1 · September 22, 2020, 7:36pm

Yes, and that is the part which I need help bro. If another parts have correlation with this part I would post them too. Why am I convincing you?

anon73444976 · September 22, 2020, 7:38pm

No, you're not convincing me.

ratatosk1 · September 22, 2020, 7:42pm

Then, help me if you know the answer?

anon73444976 · September 22, 2020, 7:45pm

Answer?
I don't even know fully what the question is
Post the code.

Robin2 · September 22, 2020, 8:53pm

ratatosk1:
Yes, and that is the part which I need help bro.

Please post the complete program. Often the reason you can't find the cause of the error is because it is not in the piece of code where you think it is.

...R

ratatosk1 · September 24, 2020, 9:16am

Here it is

#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include <ArduinoJson.h>
#include "DFRobot_SHT20.h"



#define SIM_PWR 12




String datee = "";
String timee = "";

float latt = 0;
float longg = 0;
int gnssnum = 0;
int glonassnum = 0;

int counter = 0;
int tempr = 0;



String getSplittedValue(String data, char separator, int index)
{
  int found = 0;
  int strIndex[] = {0, -1};
  int maxIndex = data.length()-1;

  for(int i=0; i<=maxIndex && found<=index; i++){
    if(data.charAt(i)==separator || i==maxIndex){
        found++;
        strIndex[0] = strIndex[1]+1;
        strIndex[1] = (i == maxIndex) ? i+1 : i;
    }
  }

  return found>index ? data.substring(strIndex[0], strIndex[1]) : "";
}


int sendCommand(String cmd, String answer, int delay_time)
{
    Serial1.println(cmd);
    Serial.flush();
    Serial1.flush();
    delay(delay_time);
    while(Serial1.available())
    {
        String ans = Serial1.readString();
    
        if(ans.equals(answer))
        {
            return 1;
        }
    }
    
    return 0;

}

void sendSingleCommand(String cmd, int delay_time)
{
    Serial1.println(cmd);
    delay(delay_time);
    Serial.flush();
    Serial1.flush();
}


void showMessage()
{
   Serial1.flush();
   Serial.flush();
   while(Serial1.available())
   {
      Serial.println(Serial1.readString());
   }
}

String showMessageS()
{
  String mes = "";
  Serial1.flush();
  Serial.flush();
  while(Serial1.available())
   {
      mes = Serial1.readString();
   }

  return mes;
}

void powerTrigger()
{
    Serial.println("Device is enabling..");
    digitalWrite(SIM_PWR, HIGH);
    delay(3000);
    digitalWrite(SIM_PWR,LOW);
}

void setGPRS()
{
    int r = sendCommand("AT+SAPBR=3,1,\"Contype\",\"GPRS\"", "OK", 150); //300
    Serial1.flush();
    Serial.flush();
    r = sendCommand("AT+SAPBR=3,1,\"APN\",\"INTERNET\"","OK", 150); //300
    r = sendCommand("AT+SAPBR=1,1", "OK", 150); //300
       
    Serial.println("GPRS Enabled");
}

void closeGPRS()
{
    int r = sendCommand("AT+SAPBR=0,1", "OK", 10); //300
    Serial1.flush();
    Serial.flush();
}


int getGPS()
{

	sendSingleCommand("AT+CGNSINF", 350); //500
  Serial1.flush();
  Serial.flush();
  //delay(500);
  
	while(Serial1.available())
    {
        String tempAns = Serial1.readString();
       // Serial.println(tempAns);

        if(getSplittedValue(tempAns,',', 1).equals("1"))
        {
            String latS = getSplittedValue(tempAns,',',3);
            String longS = getSplittedValue(tempAns,',',4);
            String gnss = getSplittedValue(tempAns,',',15);
            String glonass = getSplittedValue(tempAns,',',16);
            
            latt = latS.toFloat();
            longg = longS.toFloat();
            gnssnum = gnss.toInt();
            glonassnum = glonass.toInt();

            Serial.print("GPS Updated: ");
            Serial.print(latt);
            Serial.print(",");
            Serial.print(longg);
            Serial.print(",");
            Serial.print(gnssnum);
            Serial.print(",");
            Serial.print(glonassnum);
            Serial.println();
            return 1;
        }
        else
        {
            Serial.println("Cannot take GPS Signal");
            return 0;
        }
    }
}

void updateDateTime()
{
    Serial.flush();
    Serial1.flush();
    sendSingleCommand("AT+CCLK?", 150); //500
	  Serial.flush();
    Serial1.flush();
    //delay(500);
    while(Serial1.available())
    {
        String tempAns = Serial1.readString();
	
        datee = getSplittedValue(tempAns,',',0);
        datee = datee.substring(datee.length()-8,datee.length());
        timee = getSplittedValue(tempAns,',',1);
        timee = timee.substring(0,8);

        Serial.print("Date time updated: ");
        Serial.print(timee);
        Serial.print(",");
        Serial.print(datee);
        Serial.println();
    }
	
}



void GPRSConfig()
{
    powerTrigger();
    delay(3000);
    sendSingleCommand("AT", 10);
    //delay(3000);
    showMessage();
    showMessage();
    //delay(2000);
    
    showMessage();
    //delay(1000);
    sendSingleCommand("AT+CLTS=1", 200);
    //delay(1000);
    showMessage();
    sendSingleCommand("AT&W", 200);
    //delay(1000);
    powerTrigger();
    delay(3000);
    powerTrigger();
    Serial.println();
   // delay(5000);
    showMessage();
    //delay(3000);
    sendSingleCommand("AT+CGNSPWR=1", 200);
    //delay(2000);
    showMessage();
    //delay(100);
    sendSingleCommand("AT+CGNSSEQ=\"GSV\"", 200);
    //delay(2000);
    //sendCommand("AT+CGNSINF", 10);
    showMessage();
    //sendCommand("AT+CGNSINF", 10);
    showMessage();
    //sendCommand("AT+CGNSINF", 10);
    showMessage();
    sendSingleCommand("AT+CGNSINF", 10);
    showMessage();
    //delay(5000);
    showMessage();
    //delay(10000);
}

void setup()
{
    Serial.begin(9600);
    Serial1.begin(9600);
    delay(2000);
    Serial.println("Device initializing...");

    pinMode(SIM_PWR, OUTPUT);

    initParts();
    GPRSConfig();
    Serial.println("Device initialized");
    delay(30000);
   
    Serial.println("Ready, Running");
    delay(1000);
    Serial.println("Configuring GPS");
    int resp = getGPS();
    while(resp!= 1)
    {
      resp = getGPS();
      delay(1000);
    }
    setGPRS();
}

void loop()
{
    Serial.println();

    tempr = getGPS(); 
	delay(1000);
}

Robin2 · September 24, 2020, 10:23am

I reckon it will be easier to get to the bottom of the this program if you write a short 10 or 20 line program that just covers the essentials.

...R

cattledog · September 24, 2020, 4:01pm

However it readString does not give me whole the Serial1 response.
I cant get the number of gnss and glonass satellites seen

There have been two different problem statements

One, that the whole string is not present in tempAns after

String tempAns = Serial1.readString();

Two, that the entire string is present, but the parsing of two numbers from that String is faulty.

Please clarify. You may need to modify the title of your posting.

markd833 · September 24, 2020, 5:07pm

I'm still confused by the question after reading through several times.

However, if the OP is trying to read

+CGNSINF: 1,1,20200922094719.000,36.208752,36.155862,121.200,0.17,229.9,1,,1.0,1.3,0.9,,10,8,,,43,,

from the serial port, then there's a good chance that part of the problem is the 64 character receive buffer limit. If my counting is correct, that message is just shy of 100 characters. The OP will most likely have to reassemble the message in their own buffer from multiple reads of the serial port.

ratatosk1 · September 24, 2020, 6:31pm

I tought that too and tried to read Serial two times but it gave me nothing on second request

Grumpy_Mike · September 24, 2020, 7:15pm

ratatosk1:
I tought that too and tried to read Serial two times but it gave me nothing on second request

It could be that once you had read it the first time and processed the contents, you had lost the rest of the message. Better to increase the buffer size.

ratatosk1 · September 25, 2020, 10:34am

You can be right but the message it gives me 51 characters it is not full of 64. And how can i increase the buffer size of Arduino Mega? I am using Serial1 to communicate the module.

Am I going to just write

#define SERIAL1_BUFFER_SIZE 100 or something?

Grumpy_Mike · September 25, 2020, 11:16am

And how can i increase the buffer size of Arduino Mega?

Top hit on a search of “ increasing the buffer size on an Arduino Mega” gives :-
https://forum.arduino.cc/index.php?topic=399751.0

Topic		Replies	Views
how about for the Serial.read() get data Programming	10	1122	May 5, 2021
How to read serial data sent in through the GPS and to store it in a string Programming	4	1405	May 5, 2021
readString() output nothing Programming	5	629	May 5, 2021
Reading a Long string Programming	4	718	May 5, 2021
How to use Serial.read() 2 times Programming	17	4121	May 5, 2021

Serial.readString does not give whole string

Related topics