Just FYI, if you are using touch sensing on the T3, there are 12 different possible pins to use, but not all pins are equivalent. If you want the lowest noise, your best bet is pin 15 (A1). The noisiest touch values are on pin 22 and 23, I presume from adjacent-net noise coupling from chip internal layout and/or board layout. Below values were obtained by running the attached program to read and average together a set of touch sensor readings, for each of the 12 possible touch pins. This is on a T3 board with edge pins soldered, but held in midair by the USB cable: not plugged into a breadboard and with nothing else connected. The Average, Peak-to-Peak (max - min) and Standard Deviation are sent out from the program, and in this case each number shown below is the average of 181 sets of readings, over about 20 minutes.
Note, pins 25-33 are on the bottom side of the board (access by SMT pads only). Pin 25 has the lowest absolute reading, indicating the shortest net with least coupling to the ground plane.
Incidentally, the calibration of the touch sensor is as advertised, 1 count = 0.02 pF at least within 10%. A 10 pF test capacitor I have showed a delta of 496 counts when connected.
From this chart it actually looks like pin 15 isn't even working, since the reading almost never budges even a single count. However I verified by connecting a short wire to the pin, that it does respond as expected. Not sure why it has so much lower noise than the rest, maybe specific to operation of my code (?)
Note, pins 25-33 are on the bottom side of the board (access by SMT pads only). Pin 25 has the lowest absolute reading, indicating the shortest net with least coupling to the ground plane.
Incidentally, the calibration of the touch sensor is as advertised, 1 count = 0.02 pF at least within 10%. A 10 pF test capacitor I have showed a delta of 496 counts when connected.
Code:
Pin # Avg Pk-Pk St.Dev.
----------------------------------
0 415.92 1.52 0.23
1 424.79 2.96 0.40
15 401.00 0.01 0.00
16 372.27 1.76 0.42
17 449.68 14.42 2.01
18 604.84 6.53 0.85
19 618.47 3.38 0.56
22 516.41 48.76 7.08
23 626.27 52.35 8.54
25 282.78 1.00 0.37
32 305.06 6.65 1.06
33 315.89 20.36 2.48
From this chart it actually looks like pin 15 isn't even working, since the reading almost never budges even a single count. However I verified by connecting a short wire to the pin, that it does respond as expected. Not sure why it has so much lower noise than the rest, maybe specific to operation of my code (?)
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