|97S Interfacing / 19C print head replacement|
Message #5 Posted by BobVA on 31 July 2011, 4:41 p.m.,
in response to message #4 by Geoff Quickfall
... I watched it happen but was not quick enough to save it.
Uggh - I HATE it when something like that happens. My sympathies.
I'll keep my fingers crossed that TAS offers up the right half of a bisected 97 to you (perhaps the victim an unfortunate industrial accident in a saw mill.) They tend to work so well, that may be what it takes to get a junker. I've got one parts machine, but unfortunately it didn't have the printer assembly when I got it. (And some guy was standing on it at a ham fest.)
Thanks for that pointer. I've added that to "The List of Stuff I've Got To Do". Looks like a nice project. I haven't written any interrupt driven code in a decade or more, so I was glad to see you didn't need any. I'm pretty familiar with the BS2, so perhaps I'll be able to grasp the SX.
The photos were also interesting - whoever swiped the cable from my 97s didn't have the courtesy to replace the cap on the IDC connector.
I recently built a clock from a old power plant tachometer (whose scale was handily was numbered zero to twelve) using a BS2, a DAC to drive the meter movement and a 1302 RTC. One gimmick from that that you may find handy: I wrote a "signal" byte (i.e. known value) at the start of the 1302 RAM. My code uses it as a start-up check to detect a back-up power failure and react accordingly. (I'm using a cap for backup, so it's only good for a couple of days.) Might be fun to do something similar with your circuit, perhaps writing a checksum of bytes 0-30 in byte 31.
I'd been idly thinking about building a PC interface box for a spare 97 card reader to allow a PC to read/write 67/97 cards, but I'm now thinking the approach you suggested is a *lot* simpler.
Sending a program from a PC to the 97 using your interface looks pretty straight-forward, and I think that would cover 95% of the use cases for such an arrangement. (Probably not that much call for reading a card into a PC.)
PS: While I had the hood up on the 97, I used the technique described in this post of jumping test points "F" and "H" on the reader circuit board to allow writing to a write-protected card (I needed to fix a damaged HP Standard Pac card). It got me thinking about adding a switch to do this in the future, but perhaps it would be an ideal "f" function to add to your board (driving a reed relay to close the circuit between the points.)
Edited: 31 July 2011, 5:07 p.m.