Arty Board Core Supply Current Monitoring

[navinkumar2015]

I am using a Digilent artix7 FPGA board(ARTY) to measure core power used by the FPGA.

Reference manual says "A current sense amplifier (IC15, Texas Instruments INA199A1) connected across the sense resistor provides a gain of 50 and produces an output voltage of 500 millivolts per amp of current"

Does it mean If I get a voltage reading of 0.10 volts at output of XADC( channel 10), current drawn is equal to 0.2 Amperes? or do i need to consider anything else?

Also, I am using this current and multiply with voltage to power. Doing so, I am getting on board power one half of power estimated by the tool. (looks wrong)

Please advice!

[jpeyron]

Hi @navinkumar2015,

So for every .5V it is equal to 1A of current.  Your math looks right. If you have .1V then it would be .2A. The only thing I see from the reference manual that you need to do is configure Channel 10 of the XADC as a unipolar input. 

cheers,

Jon 

[navinkumar2015]

Thanks for your inputs jpeyron.

I configured channel 10 as unipolar input.  For power ,voltage is measured using MSB 12 bits, say x"040" correspond to 0.0156 volts  ( 64/4096 * 1V ). I think this calculation is correct. 

[jpeyron]

Hi @navinkumar2015,

Your calculations look correct and with x"040" correspond to 0.0156 V which is .03125 A. You mentioned a tool in your first post. So what tools are you using? could you attach screen shots?

thank you,

Jon

[navinkumar2015]

Hi @jpeyron,

Thank you for the details. I generated .saif file from simulation data and used Xilinx Vivado power analyzer to measure the estimated power.

Attaching the vivado screenshot.

For the same design, i am getting 129 mW as on board power.

[jpeyron]

Hi @navinkumar2015,

Can you attach your block design or hdl code?  How are you acquiring the data for channel 10 ( e.g. multimeter on the v_p pin on the arduino header)? I was wondering if adding sampling in the XADC would help?

cheers,

Jon

[navinkumar2015]

Hi @jpeyron

I have attached the block design snapshot.

I am reading voltage values using AXI Lite interface. Ex: -address 44A00268 for channel 10. Please let me know if any issues with this approach.

 

Thank you very much for taking time to look into issue. 

Edit1 :

Any thoughts on this?

Regards,

navin

[jpeyron]

Hi @navinkumar2015,

Have you tried reading the data from the V_P pin on the Arduino header? Did you try adding sampling?

cheers,

Jon

[jpeyron]

Hi @navinkumar2015,

Could you please attach screen shots of what you are seeing. Where are you getting 129mW?  Are you using the previous Amperes and Volts that you posted earlier? If so I am not getting the same number for Power. P/1.8V = .03125A . P = .05625 W.

cheers,

Jon

[navinkumar2015]

On 5/27/2017 at 0:48 AM, navinkumar2015 said:

Hi @jpeyron

In the above design XADC is a slave to JTAG master ( with address 44A00000).  I run the command in Vivado tcl console (After programming device)

run_hw_axi [create_hw_axi_txn rd [get_hw_axis hw_axi_1] -address 44A00268 -len 1  -type read -f] returns
INFO: [Labtoolstcl 44-481] READ DATA is: 00001164

MSB 12 bits are channel 10 read data from ARTY board = x"116"  = ~ 0.136Amps, As core voltage(VCCINT)is 0.95, power P = 0.136* 0.95 = 129 mW

But this off from estimate( which is around 460 mW). 

Numbers i used previously (0.03125A) are not related to this project. 

Regards

 

 

[jpeyron]

Hi @navinkumar2015,

I did some more research and the circuit monitors only VccINT and VccBRAM. Your power summary number you are using including much more than this. If you add the VccINT and VccBRAM together from the power report you should be getting the same number. I included a screen shot of where you should be looking.

cheers,

Jon 

[navinkumar2015]

Hi @jpeyron,

Thanks for your efforts. I realized that i need to consider only Vccint/VccBram.

Is there any way to measure vccaux power on arty board ?  MMCM i am using in my design uses this Vccaux supply.

Thanks,

Navin

[jpeyron]

Hi @navinkumar2015,

Unfortunately, I do not see a way to measure VccAUX specifically. I see we have current monitoring for the 5v and the 5v external but neither of these would be helpful to get VccAUX.

thank you,

Jon

[navinkumar2015]

Hi @jpeyron

Thanks for your inputs. 

Regards,

Navin