Unusual serial readings from Trill Craft on Teensy

alexaudio

Hi,

I'm trying out the Arduino example 'craft-print.ino' on a Teensy 4.0. The serial readings I'm receiving seem incorrect. It looks like I'm getting maximum values on the first five pins then nothing on the other pins. I've tried pull-up resistors (4.4 K) on the SDA and SCL lines but to no avail. Could I be missing something?

Below is an image of my breadboard circuit plus a video of the readings I receive when touching pin 0. Thanks in advance for any help!

alt text

giuliomoro

It could be that it is set in Centroid mode?
Can you show your code?

alexaudio

Sure, it's just the craft_print.ino example:

/*
 ____  _____ _        _
| __ )| ____| |      / \
|  _ \|  _| | |     / _ \
| |_) | |___| |___ / ___ \
|____/|_____|_____/_/   \_\
http://bela.io

\example craft-print

Trill Craft Print
=================

This is an example of how to communicate with the Trill Craft
sensor using the Trill Arduino library.

The sensor is set to Differential mode and readings from each of the
capacitive connections on the sensor ar eprinted to the serial port.
*/

#include <Trill.h>

Trill trillSensor; // for Trill Craft

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  int ret = trillSensor.begin(Trill::TRILL_CRAFT);
  if(ret != 0) {
    Serial.println("failed to initialise trillSensor");
    Serial.print("Error code: ");
    Serial.println(ret);
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(100);
  trillSensor.requestRawData();

  if(trillSensor.rawDataAvailable() > 0) {
    while(trillSensor.rawDataAvailable() > 0) {
      int data = trillSensor.rawDataRead();
      if(data < 1000)
        Serial.print(0);
      if(data < 100)
        Serial.print(0);
      if(data < 10)
        Serial.print(0);
      Serial.print(data);
      Serial.print(" ");
    }
    Serial.println("");
  }
}

giuliomoro

OK, found the bug hopefully (which really is platform-specific, the Teensy 4.0 is much faster than the Arduino UNO we have done most of our tests on) and updated the library. Can you get the latest version and try again?

alexaudio

That did the trick! Thanks very much!

giuliomoro

Thanks for confirming that

alexaudio

Although after trying this further, I think there may still be some issues...

All pins respond when touched directly on the Trill board. If I connect a jumper lead, via the breadboard, and touch that, only certain pins respond. I'm reflashing the Teensy each time I reconnect the jumper lead.

giuliomoro

That may be expected. When the program starts, the "baseline" reading for each pad is reset, which means that you should not be touching any of the pads (or the wires connected to them) when the program starts. Also, adding wires to a pad may mean that you are saturating its reading and that you may have to switch to a lower value of the prescaler (intuitively, that's a sort of "analog gain" of each pad). The best way to figure out these two issues is to temporarily set your Trill Craft to raw mode (i.e.: call trillSensor.setMode(Trill::RAW) at the end of setup()) and have a look at the readings that come in.
More details can be found at this page;

You may also want to try out the craft-settings example, which provides a serial interface to interactively change settings.

alexaudio

Thanks Giulio!