Can't figure out physical connections for Basys3 XADC Demo

[Zain Zaidi]

Hello,

Merry Christmas hope you guys are doing great. I am a beginner in digital design course and i want to implement this xadc demo project from digilentinc reference on my Basys3 FPGA. I'm having problems on the step 4 which is running the project as i can't figure the physical connections to connect to the JAXDC port on FPGA. 

 

Can someone confirm if the connections i have done in this picture are right?

One last question. When you open the XADC Basys3 Demo project and see its constraints, only package pins i don't understand are these A12,B13 ones. Where are they located on FPGA? I'm assuming there are some internal connections like seven segment decoder have.

 

Any help appreciated. Thank You.

Regards,

Zain

 

[Ana-Maria Balas]

Hello @Zain Zaidi,

The JAXC6 and JAXC12 provides 3.3V VCC and are not inputs.

The ADC differential input must be with a voltage difference between 0-1V.

The input signal for each JXADC channel of the Pmod must be between 0 - 3.3V.

So if you connect your XA_N channels to ground, then you must apply to the XA_P channels a voltage between 0-1V.

ex :   XA1_P= 0.5sin(wt), XA1_N = 0V   => XA1_P - XA1_N = 0.5sin(wt) differential input for ADC.

XA1_P= 2.5sin(wt), XA1_N = 2.2sin(wt)   => XA1_P - XA1_N = 0.3sin(wt) differential input for +ADC.

Please read ug480  pages 31-32.

If you look into the schematic file of the Basys 3, you will see that the Vp(A12) and Vn(B13) pins are connected to XADCGND.