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USB4VC/captures/usb delay notes.txt
2021-10-22 23:38:24 +01:00

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449 B
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very useful video:
https://youtu.be/wdgULBpRoXk
search for PID ACK for data packet
from keypress to PID ACK on USB line: 10 to 20ms
catting /dev/input/event0 in bash: 490us
printing via python3: 1ms
script below:
fff = open("/dev/input/event0", "rb" )
while 1:
data = fff.read(24)
print(data)
using queue to despatch SPI on raspberry 3: 700 to 800us
on lichee 3.5ms
hand parse raw dev/input: 470us on pi3, 1ms on lichee
32 byte fixed