I’ve got a FSLP connected to a Teensy 4.1 board.
I know that you are supposed to trim the length of the FSLP per the Customization GUIDE. I have mine trimmed as in Fig. 4 of the guide, like this:
I’ve followed the directions in the FSLP-Integration-Guide-13.pdf to hook it up and it is generally working. I have SL connected to A12, D1 to 29, DL2 to A13 and BotRo to 28.
However, I have a problem with the impedance of the pin of the microprocessor (IMXRT1060CEC) that is connected to the bottom of Ro. The datasheet for the microprocessor says that when the pin is an input it has a R_Keeper (keeper circuit resistance) connected of about 105k to 175k ohms.
So, what is happening (i think) is that this R_Keeper is connected to the 3.3V internally in the microprocessor and it is screwing up the position measurement. The position is dependent on how hard i press. So when I press my finger in the center of the FSLP i don’t get near the center value out for position, unless I press really hard.
How might I fix this?
I tried an additional pull down resistor from the bottom of Ro to ground, and this helps, but it doesn’t seem like it would be very accurate (from board to board for example).