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Proof of concept serial adapter for the Z80 Card

September 2, 2015

 The Z80 front panel card can accept either RS 232 or TTL level serial but it wants the polarity opposite to what you get from a regular FTDI cable. I goobered this together using a 7404 inverter to switch the signals just to make sure I understood the connections.
The eventual olduino/Z board will replace the front panel and I can do what I like for wiring and adjust the software accordingly but I’d like to play with this for a while before I build my own board which means making a little more stable adapter.

With this lashup the onboard serial monitor responded right away and worked as advertised. It looks very handy for getting my bootloader going and if there’s room in the rom it would make sense to leave it all there.
15-09-02 serial monitor

I had thought there was a way to tell the FTDI chip to invert the signals but I am either misremembering or not finding it I’ll keep googling around.

Update: Yep, you can tell the FTDI chip to invert the signals which will at least get rid of the inverter. I have a spare FTDI friend that I can invert and use just for this. The pins still won’t line up very well but that’s less of an issue. Lee likes to do things old school but I’m going to recomment that he seriously consider redoing the serial connection to accept the FTDI cable pinout and polarity.
I found FT_PROG courtesy of
15-09-02 ftdi invert

This is a bit more practical looking. I have visions of mounting a 6 position female header flat on the front panel board and doing the wiring and capacitor between that and the holes for the existing male header which I would remove.
15-09-02 inverted


From → Olduino/Z

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