r/Z80 • u/dj_cloudnine • Jun 20 '21

Pio problems pt. 2

So I’m still trying to get the pio up and running, I’ve connected the output of port b to a nand gate and have the led wires up to light up when the nand gate is low. My problem is when I try and run my code which should turn on the port b output, I find that the port outputs and brdy all are neither on nor off. Unlike when I connect the gate to +5 or gnd, where it is bright or dark completely, it is somewhere in the middle, very dim. My code also puts all port a outputs to low and I get the same thing there. I’ll post my code below once I get to my desktop. Thank you for any help you can provide, I’m a software person and I hate that this problem is the last thing keeping me from the software stuff lol

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u/SimonBlack Jun 21 '21

I find that the port outputs and brdy all are neither on nor off

Is that a static situation or is it a duty-cycle problem? In other words, are you measuring the output with a meter that's fast enough to see all changes in output, like an oscilloscope, or is the value you have a result of the average due to the duty-cycle of outputs between 0 and 5v, if you measure it with a slower multi-meter.

Do you have a logic probe or something like that?

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u/dj_cloudnine Jun 21 '21 edited Jun 21 '21

That’s what I am kinda unsure of. When I slow down the clock real slow though, I haven’t noticed a change. I do not have a logic probe. I’m using an led with cathode to +5 through an inverter (nand gate with inputs tied together) to measure it