ttn decoded data is different to display/serial console data

[muckisg]

Hi,

i was asked to start a new issue. I am working with a T-Beam V1.0 and realized all steps from the readme file.
My T-Beam display and serial console show the right gps coordinates but using the decoder script from the readme with ttn show different results.

TTN output:

Serial console output:

any ideas?

Thanks in advance,

Maurice aka muckisg

[kizniche]

This is a strange issue. I can't immediately think of anything that would cause this. Give me some time to think of potential causes. If you have any ability to debug in the meantime, please do.

[muckisg]

Yes, sure i do as far as i can. It is strange to me that the results in ttn differ from packet to packet, so that the payload seems to be interpreted completly wrong but i guess i would not be the first person to find this problem then. Could it be a byte order problem?
Thanks for your quick response by the way! :-)

[askmurphy]

I had the same problem, solved it by using another decoder, check your source and look if there more versions of the decoder inside 😀 Regards, Arthur Verstuurd vanaf mijn iPhone

…

Op 24 mrt. 2021 om 16:30 heeft Kyle Gabriel ***@***.***> het volgende geschreven:  This is a strange issue. I can't immediately think of anything that would cause this. Give me some time to think of potential causes. If you have any ability to debug in the meantime, please do. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or unsubscribe.

[muckisg]

Would you share your decoder? If this is the problem it is a structural one so that every user should have the problem as far as i can tell. Thanks in advance, MuckiSG

[muckisg]

@kizniche I tested a bit and here are my results till now:
I made a minimal sketch reading the GPS data, converting them into a payload with your code from the gps.ino and printed the payload to the serial plotter. I took the payload and tested it with the decoder from your README. That worked! So, the decoder is correct.
So i guess the payload gets corrupted somewhre. Here my testcode:

#include <TinyGPS++.h>                       
 
uint32_t LatitudeBinary;
uint32_t LongitudeBinary;
uint16_t altitudeGps;
uint8_t hdopGps;
uint8_t sats;
char t[32]; // used to sprintf for Serial output
uint8_t txBuffer[10];

TinyGPSPlus gps;                            
HardwareSerial GPS_Serial(1);                 

void setup()
{
  Serial.begin(115200);
  GPS_Serial.begin(9600, SERIAL_8N1, 34, 12);   //TX-RX
}

void loop()
{
  Serial.print("Latitude  : ");
  Serial.println(gps.location.lat(),5);
  Serial.print("Longitude : ");
  Serial.println(gps.location.lng(),5);
  Serial.print("Satellites: ");
  Serial.println(gps.satellites.value());
  Serial.print("Altitude  : ");
  Serial.print(gps.altitude.meters());
  Serial.println("M");
  Serial.print("Time      : ");
  Serial.print(gps.time.hour());
  Serial.print(":");
  Serial.print(gps.time.minute());
  Serial.print(":");
  Serial.println(gps.time.second());
  Serial.println("**********************");

    LatitudeBinary = ((gps.location.lat() + 90) / 180.0) * 16777215;
    LongitudeBinary = ((gps.location.lng() + 180) / 360.0) * 16777215;
    altitudeGps = gps.altitude.meters();
    hdopGps = gps.hdop.value() / 10;
    sats = gps.satellites.value();
    
    txBuffer[0] = ( LatitudeBinary >> 16 ) & 0xFF;
    txBuffer[1] = ( LatitudeBinary >> 8 ) & 0xFF;
    txBuffer[2] = LatitudeBinary & 0xFF;
    txBuffer[3] = ( LongitudeBinary >> 16 ) & 0xFF;
    txBuffer[4] = ( LongitudeBinary >> 8 ) & 0xFF;
    txBuffer[5] = LongitudeBinary & 0xFF;
    txBuffer[6] = ( altitudeGps >> 8 ) & 0xFF;
    txBuffer[7] = altitudeGps & 0xFF;
    txBuffer[8] = hdopGps & 0xFF;
    txBuffer[9] = sats & 0xFF;
    for (int x=0; x < 10; x++)
      {
        if (txBuffer[x] < 16)
        {
          Serial.print("0");
        }
        Serial.print(txBuffer[x], HEX);
        Serial.print(" ");
      }
     Serial.println();  
  smartDelay(1000);                                      

  if (millis() > 5000 && gps.charsProcessed() < 10)
    Serial.println(F("No GPS data received: check wiring"));
}

static void smartDelay(unsigned long ms)                
{
  unsigned long start = millis();
  do
  {
    while (GPS_Serial.available())
      gps.encode(GPS_Serial.read());
  } while (millis() - start < ms);
}

I am not that deep in your code and i am the worst coder on planet earth but i hope it helps to find the error.

sunny greetings,

Maurice

[muckisg]

FYI:
Payload within ttn_send: C8 BD 3E 85 09 0B 00 A7 12 06 <-correct
Payload in TTN console: DB DB 7D 33 F7 F0 68 50 F0 84 <- bad

Because of the fact the payload is correct within the ttn_send function, the error has to be somewhere within the trasmission or ttn handling. The payload ttn receives is definitely wrong! When i send the payload "00 01 02 03 04 05 06 07 08 09" i get totaly different resunlts on the ttn end an even changing results.

So, your software seams to be correct but do you have an idea where the error is?

Tried a second board aswell with the same results, so no hardware error.

thx, Maurice