What do Sdist and Ldist in the databot bluetooth spec measure?

pat.ryan · March 11, 2023, 4:17pm

Hi Everyone
I am looking at some of the bluetooth settings for the databot and I see ‘Sdist’ and ‘Ldist’ but I am not sure what they measure. Does anyone have any insight?

Also regardless of which one I set, the response comes back with the same response key, so it seems like you can only have one set to return data at a time, is that correct?

Thanks

dbaldwin · March 13, 2023, 5:53pm

These are related to the time of flight sensor that measures distance. SDist representing “short distance” and LDist measuring “long distance”. Check this out:

The VL53L1X offers three distance modes: short, medium, and long. Long distance mode allows the longest possible ranging distance of 4 m, but the maximum range is significantly affected by ambient light. Short distance mode is mostly immune to ambient light, but the maximum ranging distance is typically limited to 1.3 m (4.4 ft). The maximum sampling rate in short distance mode is 50 Hz while the maximum sampling rate for medium and long distance modes is 30 Hz. Performance can be improved in all modes by using lower sampling rates and longer timing budgets (as can be seen in the figure above).

From here:

and here is a code example from the databot repo:

github.com

arbotics-llc/databot_ESP32/blob/4ffdf1678f2eeecb20d00f165f0e9cc78383c278/examples/Sensors/databot_distance/databot_distance.ino#L25


      
          float distance; //variables to store the distance values
          void setup() {
          
          
  Serial.begin(9600);
            pinMode(25, OUTPUT);
            digitalWrite(25, HIGH);
          
          
  Wire.begin();
            Wire.setClock(400000);
          
          
  if (initTOF(true))
            {
              Serial.println("TOF initialization sucess");
            }
            else
            {
              Serial.println("TOF initialization fail");
            }
          
          
  RGBled.setPixelColor(0, RGBled.Color(0, 0, 255));  // LED indication to know that databot is ON
            RGBled.show();

This example uses the long distance range. If it were up to me I would just go with Ldist unless someone on the databot team mentions otherwise.