On 28/01/2022 19:41, folkert wrote:
Hi,
[]
The RPI doesn't like 5v on its GPIO pins.
So I wonder:
- can I feed the picdiv 5v on its GPIO pin while giving it a 3.3v
voltage so that it outputs 3.3v as well to the rpi pins?
- or should I use a voltage divider? I was thinking of a 4.7k ohm and
8.2k ohm resistor giving slightly less than 3.2v - will that work? or
will that attenuate the signal too much? The 50 ohm bnc cable between
the amplifier and the rpi is 3m long. Anything else I should be aware
of?
Regards,
Folkert van Heusden
PD9FVH
Folkert,
In similar circumstances I've used a resistive divider and it's worked exactly
as expected.
For such short cables there are unlikely to be any other effects you need to
take care of. You might like to see what the voltage levels are if you
terminate the 50-ohm cable with a 47-ohm resistor - it /may/ drop to 2.5V
peak-to-peak.
I would simply try it and see.
Of course, if the idea is to send PPS to the RPi getting the appropriate GPS
devices would be my preferred solution!
Oh, just looked, I would expect to see a square-wave, not the near sine-wave
your 'scope trace shows. Is it nearer to square with a much faster timebase?
Cheers,
David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv
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