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Ashirbad

Zynq board

Question

hi everyone

i have started working with vivado tool and i am implementing ppg signal on zybo board.

my doubt is wheather ppg Zynq board can be connected to cro for checking output

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Hi @Ashirbad,

I presume you are talking about this type of PPG (Wikipedia article link). Nobody at Digilent has any experience with that type of signal, though in principle if the device that is measuring the skin volume is providing an analog signal between 0 and 1V, or if it provides a digital representation of the measured signal. I do not know what "cro" is so I do not know how the Zynq board (which one are you using? The original Zybo, Zybo Z7-10, Zybo Z7-20?)

Thanks,
JColvin

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Hi @Ashirbad,

I'm not certain which development board that uses the Zynq xc7z010 chip you are referring to, but as long as the board provides 8 digital output capable pins, and a source for Vcc and ground, then yes it will be compatible with the Pmod R2R.

Let me know if you have any more questions.

Thank you,
JColvin

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Hi @Ashirbad,

Realistically, I think it will depend on your application. If you are needing an 8-bit DAC with only a single output, you may as well go with the Pmod R2R since that is a very straightforward module. On the other hand, if you need multiple DAC outputs, then you will instead need the Pmod DA4. The limitation with the Pmod DA4 is that you are limited to an output level between 0V and 2.5V, whereas the Pmod R2R is between 0V and Vcc (generally equal to 3.3V if you are using it on a Pmod host port). The Pmod DA4 also uses the SPI protocol, so from what I recall in its reference manual, you need provide 4 bytes of SPI data to generate the desired output.

The Zynq has 4 pairs of a 12-bit ADC, limited to 0V to 1V, so if the analog input provided to the ADC is in that voltage range you will be good to go.

As a clarification question, are you planning to use the DA4 to receive the output from your device and then provide the response to the XADC of the Zybo? If your device already provides a digital output, you can likely just have the Zybo read digital output directly and interpret the data without needing to use a DAC or ADC.

Thanks,
JColvin

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Hi JColvin 

I have chosen Pmod DA4: Eight 12-bit D/A Outputs (https://store.digilentinc.com/pmod-da4-eight-12-bit-d-a-outputs/) and 

Pmod R2R: Resistor Ladder D/A Converter (https://store.digilentinc.com/pmod-r2r-resistor-ladder-d-a-converter/). Could you please suggest me which would be better for implementing Digital to analog converter interfacing with Zynq board. My design give 12 bit digtal output, which DAC will be better for me. Zynq board has on board adc, does it require external adc. Clear my dout.   

Thanking You

Ashirbad

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Hi JColvin

Thanks for help

Actually I want to show my output on oscilloscope but zynq have only digital output, to connect zynq board with oscilloscope i need a DAC. Which DAC is compatible with my board ZYNQ xc7z010, i want to know . MY application need continuous output   as it is real time signal. Could you please tell me wich DAC will give continuous output.

Thanks,

Ashirbad   

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Hi @Ashirbad,

Both of the Pmods can provide continuous output once the output is set. The change in output will then be limited by each individual Pmod; about a 25 MHz update for the Pmod R2R and what appears to be about a 1.5 Mbps or so update rate for the Pmod DA4. Depending on your oscilloscope, you likely won't see a clean analog signal and will still be able to see the digital transitions from value to value for both Pmods, though the signal will technically be continuous the entire time.

Let me know if you have any other questions.

Thanks,
JColvin

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