P.S. For reading the barcode port on the M100, I think the best resource I've seen is Oppedahl's "Inside the TRS-80 Model 100" (Ch 14., pp. 231–237) which includes sample code and even a little schematic of how to use an opto-isolator so you don't blow out the port. You can either poll the port, which probably makes more sense if you are going to try to use similar code on the C64, or enable the BCR interrupt which calls whatever handler you place at address F5F9 every time it sees a "white" line.
You can get a sense for how it works with this one-liner which beeps whenever pin 2 is grounded: ```BASIC 1 IF 8 AND INP(187) THEN BEEP:GOTO 1 ELSE 1 ``` —b9 On Tue, Feb 24, 2026 at 2:14 PM B 9 <[email protected]> wrote: > Cool idea! I don't think the Bar Code Reader port has enough (any?) output > ports to address the RAM, so I'm guessing your "glue logic" is going to > spew bits to the BCR, right? What's your thought on synchronizing with the > M100? > > Whether this ends up working or not, I'd love to see whatever you come up > with. > > —b9 > > On Tue, Feb 24, 2026 at 8:33 AM scottgmcdonnell <[email protected]> > wrote: > >> It certainly would. And it has all the signals required to not need much >> additional circuitry. >> >> But it is more of a 'because I can' excercise. Speed is not a major issue >> for this. The Model 100 serial speed at the barcode port is capable of >> speeds much faster than such a camera. >> >> As well, this is not a realistic justification (doing 1980s marketing >> roleplaying here), but the average person would be more willing to plug a >> peripheral in to the barcode port. The system bus feels more 'advanced' and >> "Radioshack technician" installable. >> >> Not that this is 1984 and we are making an actual product or dealing with >> a "typical user" today. >> >> >> Anyway, just for novelty as well as the ability to make one circuit that >> works with both the C64 and the Model 100. >> >> Scott >> >> Sent from my T-Mobile 5G Device >> >> >> -------- Original message -------- >> From: "Alex ..." <[email protected]> >> Date: 2/24/26 8:51 AM (GMT-05:00) >> To: [email protected] >> Cc: [email protected] >> Subject: Re: [M100] DRAM camera capture on the Model 100 >> >> Wouldn't the system bus interface be your best bet for speed? >> >> On Tue, Feb 24, 2026 at 5:14 AM Scott McDonnell < >> [email protected]> wrote: >> >>> In my robotics group, we have been talking about an old concept of using >>> a DRAM IC as an image sensor. >>> >>> Essentially you take an old DRAM IC in ceramic package with the metal >>> lid and knock off the lid. You pre-charge the DRAM with all 1s and then >>> as light hits each cell, it drains the capacitor and will flip the bit. >>> The brighter the light, the faster it flips. >>> >>> A 4164 DRAM of this type has two 128x256 arrays with a small gap in >>> between. Generally one would just use 128x128 of one half. The camera >>> lens would be arranged to focus on that. A 4164 DRAM is a 1 bit by 64K >>> DRAM. Just one digital output. >>> >>> Now, from robot vision, my brain started working out how to off-load a >>> bunch of the scanning and glue logic, I came to the conclusion that I >>> could capture an image through the joystick port of a Commodore 64. >>> >>> And then I thought, Hmm, this should be possible on the barcode port of >>> the Model 100 as well... >>> >>> On the joystick port, I was thinking a frame sync and the one digital >>> bit. This could be modified to use a longer pulse to indicate a frame >>> start on the Model 100. >>> >>> This could be used to scan in a document or take very, very low >>> resolution images on the Model 100. >>> >>> Doing it through the barcode port would mostly just be for the novelty, >>> of course. The printer port might be the better option. >>> >>> >> >> -- >> Disclaimer: Any resemblance between the above views and those of my >> employer, my terminal, or the view out my window are purely coincidental. >> Any resemblance between the above and my own views is non-deterministic. >> The question of the existence of views in the absence of anyone to hold >> them is left as an exercise for the reader. >> The question of the existence of the reader is left as an exercise for >> the second god coefficient. (A discussion of non-orthogonal, non-integral >> polytheism is beyond the scope of this article.) Thanks /usr/games/fortune >> >
