‫Welcome to the potentiometer interface demonstration with the Arti board for the set up we have the
‫Arti board which is connected to a four digit seven segment display.
‫We are controlling each individual segment with the port J coming out of the p mod on the already and
‫then we're doing the digits select through the port.
‫J.B. Pieman can do the different digits select and we also have the potentiometer which is out here
‫on its own but we're taking the output of the potentiometer and feeding it into the zero pen on the
‫chip kit or Adreno headers on the Ardie board and with the lab to do is as we're changing the potentiometer
‫as we move this we want to display the analog to digital converter reading on the 7 segment display.
‫And we're going to be displaying this value in binary code decimal so it will be a decimal value we
‫see with the the internal X A.D.C. on the Arctic's the chip located on the Ardie board is it.
‫It uses a 12 bit Ayittey converter so the maximum value we can see is four thousand ninety six and the
‫minimum value would be zero which is what's displayed right now being that the potentiometer is turned
‫all the way to the left.
‫Now if I go ahead and start rotating the potentiometer you'll see the value increment on the 7 segment
‫display.
‫So as I increase or decrease the resistance of this potentiometer you can see the HD reading changes
‫and it keeps going up.
‫We're at four hundred twenty three 450.
‫Another thing to know.
‫The very last digit the value that appears to constantly be an 8.
‫This is because we're sampling at such a high rate we're currently sampling it approximately two hundred
‫thousand samples per second.
‫And so that last digit is going to constantly change it's probably anywhere from zero all the way up
‫to 9.
‫And so that's why it appears to be an eight.
‫All the segments appear to be valid because we're constantly sampling so says it's changing so fast
‫it appears to be stuck 8.
‫If you'd have it so you can stop the sampling.
‫Then you would see that you'd have a different value other than eight.
‫But in order to continue the display as we rotate the Pentium we have to be in a continuous sample mode.
‫So if we keep going.
‫We'll see if we go all the way to the right.
‫We should get up to 4000.
‫Now what we'll know is we can't quite reach 4000 Exactly.
‫And if I go all right you can see we get to three thousand nine hundred eighty eight.
‫And the reason we can't get to the 4000 96 is because there are several things going on.
‫If you look in the schematic of the Arti you'll see that there are several resistors and a capacitor
‫there that's feeding in the positive and negative of the analog signal and due to that we're losing
‫some voltage.
‫So we're not able to feed directly 3.3 volts into the ADC.
‫And so if I go all the way back to the left you'll notice that the value starts to decrease the 80s
‫eight to de-value and I can go all the way back to the left and get it back down to zero.
‫And that is so that's telling us that the potentiometers all the way to the left wing.
‫All the right end get almost up to 4000.
‫And so this is just to show you that you can read analog signals on your FPGA board using the X DC internal
‫IP core and so that is the potentiometer interface demonstration with the keyboard.