Shouldn't be... there aren't any open drain pins in the system. The TashTalk PIC has an active-high driver enable pin (always output) and a single pin that switches direction to do LocalTalk input and output; the transceivers have an active-high driver enable pin and an active-low receiver enable pin (both inputs), and the firmware changes direction on the LocalTalk I/O pin within one cycle (125 ns) of toggling the driver enable output pin.I haven't followed all the details of this, but could there be an output that's supposed to be open-drain and you're using push-pull outputs? That could cause problems in a two-transceiver setup where two sources could potentially drive the same signals.
I'm not sure if that would work, I think the transceiver is correctly interpreting the state of the LocalTalk bus, it's just that the bus itself takes a few microseconds to return to idle and TashTalk isn't waiting long enough. I can correct this in firmware, I just need to make sure I'm doing it in a way that doesn't break anything else in the process.If I understand correctly, the problem is that TT switches to input and then the pin goes high? What if we add a pullup?
You're welcome to try if you want to but I would think that the transceiver IC already does that - lowering the DE pin should stop it driving the LocalTalk bus at all.Mmmmh ok I see (and I tried the pullup and did not work lol), but maybe a transistor could do the trick? Basically it removes one of the two tranceivers from the bus when the LTEN pin flips?
Oh, thank goodness. =)Ok, I reprogrammed the pic and it works perfectly!