RAK13010 SDI-12 unreliable communication and missing characters

[belveder79]

I have a Stevens Waters SDI-12 sensor and I purchased two of the RAK13010 modules mounted on a RAK4631 board.

I verified that the sensor is working properly, but the data communication is not reliable and misses some characters. For example, using the RAK13010_SDI_12_Interface.ino tests, here's the outcome:

help   : Print this message
mode s : SDI-12 command mode (uppercase and ! automatically corrected) [default]
mode v : verbatim mode (text will be sent verbatim)
fb on  : Enable feedback (characters visible while typing) [default]
fb off : Disable feedback (characters not visible while typing; may be desired for developers)
(else) : send command to SDI-12 bus

9I!
jqU�ju�*2�
�3r���;M9A0289667
9I!
jqU�ju�*2�
�3r���;M9A0289667
9I!
jqU�ju�*2�
�3r���;M9A0289667
9I!
TEVENSW0560126.302GSN00289667

Calling the request for identification fails multiple times and only works 1/5 cases or so. Also the string misses characters, which is also happening when doing a measurement:

9M!
9
9D0!
�00+0.001+24.3
9D1!
�8+0.001+1.699
9D2!
296-0.038+0.174

So I know that the examples are just for demonstration purposes, but I think that something more reliable is needed to make this overall usable. I followed the conversation here and started playing around with alternatives to the RAKWireless_SDI-12 library, but it seems to become quite an effort to work around these problems...

Any thoughts?

[belveder79]

I patched one of the files like this and it seems to work now as expected...

/**
   @file RAK13010_SDI_12_Basic_Data_Request.ino
   @author rakwireless.com
   @brief  Basic Data Request to a Single Sensor.
           This is a very basic (stripped down) example where the user initiates a measurement
           and receives the results to a terminal window without typing numerous commands into
           the terminal.
   @version 0.1
   @date 2022-03-11
   @copyright Copyright (c) 2022
**/
#include "RAK13010_SDI12.h"  // Click to install library: http://librarymanager/All#RAK13010

#define TX_PIN    WB_IO6   // The pin of the SDI-12 data bus.
#define RX_PIN    WB_IO5   // The pin of the SDI-12 data bus.
#define OE        WB_IO4   // Output enable pin, active low.

#define SENSOR_ADDRESS '9'

RAK_SDI12 mySDI12(RX_PIN,TX_PIN,OE);

String sdiResponse = "";
String myCommand   = "";

void setup()
{
  pinMode(WB_IO2, OUTPUT);
  digitalWrite(WB_IO2, HIGH);  // Power the sensors.

  // Initialize Serial for debug output.
  time_t timeout = millis();
  // Serial.begin(115200,RAK_CUSTOM_MODE); // Uncomment if using RUI BSP.
	Serial.begin(115200);
  while (!Serial)
  {
    if ((millis() - timeout) < 5000)
    {
      delay(100);
    }
    else
    {
      break;
    }
  }

  Serial.println("Opening SDI-12 bus.");
  mySDI12.begin();
  delay(500);

  mySDI12.forceListen();
  Serial.println("Waiting for input:");
}

  static uint8_t serialMsgRflag = 0;

void loop() 
{
  static String  sdiMsgStr;
  static boolean sdiMsgReady = false;
  
  if (Serial.available()) 
  {
    char inByte1 = Serial.read();
    if ((inByte1 == '\r' || inByte1 == '\n') && !serialMsgRflag) 
    {
      serialMsgRflag = 1;
      Serial.println("== START ==");
    } 
  }

  int avail = mySDI12.available();
  if (avail < 0) 
  {
    mySDI12.clearBuffer();  // Buffer is full,clear.
  }  
  else if (avail > 0)  
  {
    for (int a = 0; a < avail; a++) 
    {
      char inByte2 = mySDI12.read();
      if (inByte2 == '\n') 
      {
        Serial.println("== OK ==");
        sdiMsgReady = true;
      } 
      else 
      {
        sdiMsgStr += String(inByte2);
      }
    }
  }

  if (sdiMsgReady)
  {
    Serial.println("R: "+ sdiMsgStr);
    sdiMsgReady = false;  // Reset String for next SDI-12 message.
    sdiMsgStr   = "";
    if(serialMsgRflag == 2)
    {
      serialMsgRflag = 3;
    }
    if(serialMsgRflag == 4)
    {
      serialMsgRflag = 5;
    }
    if(serialMsgRflag == 6)
    {
      serialMsgRflag = 7;
    }
    if(serialMsgRflag == 8)
    {
      serialMsgRflag = 9;
    }    
  }

  if (serialMsgRflag)
  {
    if(serialMsgRflag == 1)
    {
      serialMsgRflag = 2;
      mySDI12.sendCommand(String(SENSOR_ADDRESS) + "I!");
      Serial.println("T: "+ String(SENSOR_ADDRESS) + "I!");
    }
    if(serialMsgRflag == 3)
    {
      serialMsgRflag = 4;
      delay(2000);
      mySDI12.sendCommand(String(SENSOR_ADDRESS) + "M!");
      Serial.println("T: "+ String(SENSOR_ADDRESS) + "M!");
    }
    if(serialMsgRflag == 5)
    {
      serialMsgRflag = 6;
      delay(2000);
      mySDI12.sendCommand(String(SENSOR_ADDRESS) + "D0!");
      Serial.println("T: "+ String(SENSOR_ADDRESS) + "D0!");
      mySDI12.clearBuffer();
    }
    if(serialMsgRflag == 7)
    {
      serialMsgRflag = 8;
      delay(2000);
      mySDI12.sendCommand(String(SENSOR_ADDRESS) + "D1!");
      Serial.println("T: "+ String(SENSOR_ADDRESS) + "D1!");
      mySDI12.clearBuffer();
    }
    if(serialMsgRflag == 9)
    {
      serialMsgRflag = 0;
      delay(2000);
      mySDI12.sendCommand(String(SENSOR_ADDRESS) + "D2!");
      Serial.println("T: "+ String(SENSOR_ADDRESS) + "D2!");
      mySDI12.clearBuffer();
    }
  }
}

gives

Opening SDI-12 bus.
Waiting for input:
== START ==
T: 9I!
== OK ==
R: 912STEVENSW0560126.302GSN00289667
T: 9M!
== OK ==
R: 90029
T: 9D0!
== OK ==
R: 9+0.000+0.001+25.2
T: 9D1!
== OK ==
R: 9+77.4+0.001+1.703
T: 9D2!
== OK ==
R: 9+0.295-0.038+0.173

Still not sure how to integrate the RAK13010 into something bigger like meshtastic or meshcore, if the timing is such an issue