How to use PYNQ to read a GPIO value continuously？

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1

Hi, everyone!
How can I use PYNQ to read a GPIO value continuously？

1 Like
2

Hi!

How fast? If you’re talking Python-fast, I think you could set up an AXI GPIO controller, and get python to read the mem-mapped interface.

For something faster to you would need to store the data in a buffer, so you would be limited by those resources. But then you could capture at 200hmhz+

3

Hi!

The frequency of value is about 250kHz. Actually I have used an AXI GPIO controller and I tried to use while loop to read the value. But it seems like while loop can’t catch up (can’t synchronize with) such a high frequency so I lost some values.

Here is my block design and the code in Python.

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image1186×463 37.9 KB 

from pynq import Overlay
from pynq.lib import AxiGPIO
from time import sleep
from pynq import GPIO

data = []

overlay = Overlay('/home/xilinx/pynq/overlays/overlay_1230/test1230_1725.bit')

input_ip = overlay.ip_dict['led2']
ipt = AxiGPIO(input_ip).channel1
ipt.setdirection("in")

while 1:
    data.append(ipt.read())
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4

So could you tell me how to store the data in a buffer or what’s the problem in my design and code?

5

Look up DMA on Pynq. It’s more complicated, and you will need extra stuff to control the DMA IP. But I think it’s the only way at 250 mhz.

6

Thanks.