matthew180

*nods* Sorry if I came across harsh. It always sounds better and kinder in person.

Use emulation then? Or stick with your PEB. Or sell the PEB to pay for the TIPI... This is a hobby, so spending lots of money is pretty much in the definition. These devices are made by regular people here in the community who put a lot of their own time, money, and effort into creating the devices. And then even more time and effort to make them into some thing people can just buy and plug in. This is no small effort and it is not cheap. People selling and supporting their devices deserve to recuperate the time and life they gave up to make it available for others. I'm sure the designs for the TIPI and SAMS are out there for anyone who wants to make their own PCB and assemble the devices. Don't know, I bought them both.

No, not really. I would like to, but the chips I'm using are a PITA to put on a breadboard, and sometimes the parts are only available in SMD, and the frequencies are too high (100MHz access to an SRAM or SPI Flash is not really going to work on a breadboard). Digital logic is pretty straight forward, the hardest parts are the analog bits, and of course noise (which is only worse on a breadboard). But it depends on what you are doing, so sometimes it makes sense (to prototype on a breadboard), sometimes not. For the F18A, I developed initially using an FPGA devboard that had the FPGA I was going to use, and I made a cable to plug into the 9918A socket on the host computer (99/4A in this case, see photos). Once it was mostly working, I went directly to a custom PCB, and it took three revisions to work out the electronic problems. You can use simulation these days too, to great effect, especially for digital stuff. You can also use HDLs (VHDL, Verilog, etc.) to write simulations, test them, see the timing diagrams, and use that to prove you circuits that you build with discrete logic. HDL is not just for programmable logic. Photos are of F18A early days of development.

No need to justify anything, I'm just giving my thoughts as I look at the board. Apologizes if it came across any differently. Paying attention to your design rules (based heavily on what PCB house you use), and getting them set up first, will make your life much easier in the long run. Trace / space is a big one, keep-out and distance between components, and via drill to annular ring size are important. Having a clear and detailed silk screen will make your future-self very happy when you go to do assembly and troubleshooting.

Why is U8 so close to the edge? You have a ton of unused space on the board, I would keep things well back from the edges. Consider spending some time working on the silk screen to make all the labels big, clear, easily visible, and add any information you need to configure the card. Every component should have a designation, and make sure all pin-1 designators are clear. It is hard to tell, but the input power trace to the regulator looks like any other trace; you are paying for the layer, so use the copper. Also, the regulator is close to the edge, which I realize is typical, but I never understood why they were done what way. IIRC, the regulators would also short out to the metal case if assembly was done incorrectly. No need to perpetuate a problematic design. What trace/space are you using for signals, and what are the specs for the vias? Edit: These are just my thoughts as I look at the board, they are not intended to be criticism. Just things you might want to consider.

https://github.com/hneemann/Digital "Direct export of JEDEC files which you can flash to a GAL16v8 or a GAL22v10." GALs are getting harder to find support for, and the best options seem to be some form of PALASM, CUPL, or ABEL, and some various of the open source tools. I was recently introduced to Renesas "GreenPak" devices, which come in small packages and can cost as little as $0.50 (a 20-pin device that would easily replace a GAL is about $1.32). It has current software support for Linux, MAC, Windows, and the screenshots look very schematic and drag-n-drop. The specs of the devices are nice and it appears they can go to 5V Vcc, and therefore can support 5V TTL directly. I have not used any yet, but they look nice. https://www.renesas.com/us/en/products/programmable-mixed-signal-asic-ip-products/greenpak-programmable-mixed-signal-products As for validating your PALASM, I hope someone who knows the language and has some spare cycles will chime in. It looks easy enough, and if your chip works as expected then that is probably the best validation you can get.

What manufacturer and specific part number did you end up with, and what programming tools are you using? When I was doing PAL/GAL programming, I used Lattice ispLeveler Classic, which allows writing the logic using HDL (VHDL in my case). I never learned PALASM, and although it looks somewhat straight forward, using an HDL would be easier, faster, less error prone, IMO.

Oh, interesting. If there was a manufacturing reason for a particular orientation then for sure that would take a priority. I didn't know that.

True, but computer graphics on a CRT go back as far as 1963 with Ivan Sutherland's Sketchpad, which can do things I still can't do today. Then in 1968 Douglas Engelbart gave the Mother of All Demos (you should really watch this in YT, along with videos about Sketchpad). In 1973 Xerox created the Alto with 808x606 GUI, mouse, Ethernet, GUI, etc.. The Alto was not commercially available, but it heavily influenced the 1980 PERQ-1 (which is consider the first commercial workstation). But before that, there were systems with frame buffers doing amazing things. "The Works" never-finished animated short from New York Institute of Technology was started in 1979 with some very impressive 3D rendering capability. And the hardware used for movies like TRON was being built many years before the movie released in 1982. So, we had these great things, then IBM gave us CGA... I understand the memory cost aspect, but memory prices dropped quickly during the 80s, but by then we were stuck with the myth of compatibility. I don't think that was a consideration. IBM was not into computer graphics, and their mainframes were not involved in that kind of stuff. It was mostly research computers from MIT or other schools, or places like PARC. Also, the PC was made in secret division of IBM in Boca Raton, away from the corporate prying eyes and influences, and my understanding from reading various accounts is, they could do pretty much what they wanted when creating the PC. I think cost drove most of the decisions though.

This thread prompted me to better nail down the events of my 99/4A history. After searching through a lot of magazines between 1981 and 1984 (thanks archive.org !!), I discovered a few things that I never knew, totally forgot, or was just oblivious to: 1. I got my 99/4A in July 1983 (I turned 13 in July) right in the middle of the $149 with a $50 rebate phase (so a $99 computer). This was right on the heels of the $299 with a $100 rebate phase, and just before TI announced they were exiting (sometime in the fall), which caused the price to then drop to ~$50 in November 1984. It was interesting to watch the prices dropping every few months in the magazine ads selling systems. 2. I did not realize the price war between TI and Commodore was with the 99/4A vs the VIC20!?!? That was really really really stupid of TI!! Even more stupid than I thought they were. I always thought the price war was between the Atari 400, the C64, and the 99/4A. There was no way TI could compete with the VIC20, and Commodore still got to sell the C64 for a good profit. TI should have kept the 99/4A up in price with the C64 at the very least, and promoted software rather than trying to force licensing. Really stupid. 3. By October 1983 Sears (and everywhere else) was blowing out their TI inventory, and a PEB with SSSD, disk controller, 32K, E/A, and LOGO 2 was available for $399. I remember my dad took me to get one, which I really did not understand how we could afford that because we were not that well off. Sears was out of stock, so my dad got a rain-check; I only remember that because I did not know what a rain-check was, I only knew we were leaving without a PEB... Apparently Sears called in mid December that our PEB was in stock and my dad gave it to me for xmas. I had totally forgotten about it by then, and was not expecting that under the tree. Best xmas ever! 4. The 99/4A was released in June 1981, the IBM PC was released Aug 1981. It must have been down hill for TI from then on. I was oblivious to computers at this time (11/12 years old), and it was not until 1983 when I got the 99/4A that I seem to have become aware of, and really interested in, computers other than arcade coin-op games. 5. In Feb 1982, Compaq was started by three TI engineers who got fed up and left. I had no idea. 6. There were awesome computer graphics in the late 70s and early 80s (even before TRON), and the home computer, as well as the lame CGA/EGA in the PC, were just horrible and a huge step backwards. Yeah, I know, memory and cost, but memory prices dropped rapidly, yet we were then stuck with crappy hardware until the mid 90s. IMO, computers were way more interesting BITD!

Wow, I have never seen anything like that, they sure are cute, but VERY expensive. I would only use these if I were making a one-off board for myself, and if I *really* wanted that aesthetic. Otherwise, there are colored DIP jumper shunts of all sorts that will work just as well.

The KiCAD documentation is really up to date since they have money now to pay someone to maintain it. Also, the forum is very active, as is the KiCAD Discord channel. There are also a lot of videos on KiCAD popping up due to its increased popularity in the last few years. Don't let yourself get frustrated before asking for help. Everyone has this idea that components are complicated (probably because they are in other EDA programs), or that things like multiple schematic sheets are also complicated. Most things in KiCAD are really very straight forward, they just take a little understanding on how things are set up. Components just take an amount of detail, especially in the footprint, and getting the 3D STEP model aligned to the footprint can be a little confusing the first time through. But none of it is hard, and it does not take long once you get the hang of it. You will be glad you learned.

Heh, around here you are a baby. I was 12 in 1982 when I got my 99/4A. We were a single income family and I don't know how my parents managed to afford the computer. My dad bought it from JC Penny's when the cost was $150. He was deciding between the 99/4A and C64 (both were about the same price), but he knew the TI brand from having a SR-56 programmable calculator, so that's what he picked.

A "library" in KiCAD is currently just a single file that contains symbols. The file can be anywhere you want. Footprints are their own files that you put into a folder. 3D models are also their own files that you put into a folder. If you stick the library file, and footprint / model folders into a parent folder, then you have a self-contained "complete" library that you can move around and / or use with all your designs. Why multiple symbols are contained in a single file vs. footprints being their own files is probably just legacy. Adding your own components is easy, and I recommend you make your own library to put your parts into rather than mixing them in with the stock libraries. I have a github page for my KiCAD library with some instructions on setting up your own library: https://github.com/dnotq/dnotq_kicad_lib Just substitute your own library name and environment variable with whatever you want for your own use. Use FreeCAD and the KiCAD-StepUp plug-in to align a STEP model with a footprint. Components are extremely easy in KiCAD (better than other EDA programs I have used). There are three pieces to a complete component: 1. Symbol 2. Footprint 3. 3D model The really nice thing about KiCAD is the symbols are completely separate from the footprints. This is extremely helpful when you have the same part that is available in many footprints (microcontrollers and FPGAs fall into this category, as do SMD passives like caps and resistors). You add symbols to your schematic and wire them up. You then choose the specific footprint to use for each symbol. KiCAD associates symbol pins to footprint pads/holes based on name. So if your symbol has pins 1, 2, and 3, then those pins will associate with pads named 1, 2, and 3 on a footprint. Symbol pin names, and footprint pad names do not have to be numeric. For something like and FPGA, they are usually a alpha-numeric grid, like A1, A2, A3, etc.. As long as a symbol pin name matches a footprint pad name, they will be associated. KiCAD will also associate all footprint pads of the same name, with a symbol pin of the same name. This is common for things like mechanical shields on connectors. The shield does not actually have a pin number, but many times you need to tie it to ground. Pin 0 (zero) it typically used for this. In the symbol you make as many 0-pins as you want (sometimes you only have 1 pin on the symbol for all the shield pins, or you can have one 0-pin in the symbol for each shield pin; however you like). Then in the footprint you name all such mechanical pads as 0. In the schematic you can wire the shield to ground and it will be properly associated to all the footprint mechanical shield mounts; and the PCB editor will show them as tied to ground. You can also make your own symbol and use a stock footprint (KiCAD has thousands for footprints that will cover all the industry standard footprints, and lots that are unique), or make your own footprint (I always make my own, but that is just me). You can also use a stock symbol and make your own footprint. It is all up to you. Having a 3D model associated with your footprint is very helpful for the 3D preview / rending of your board. 3D models are not required, but highly recommended. Most of the footprints that come with KiCAD will have 3D models. And for your own footprints, you can usually download the STEP model from the manufacturer these days, or find it on SnapEDA. For the variable capacitor, I see two symbols in KiCAD that should work fine for the schematic: 1. Device > C_Trim 2. Device > C_Variable Those are two-pin symbols that you can use in your schematic. The footprint you use for the device depends on what part you actually decide to use. You can even use a 3-pin footprint with the 2-pin symbol, in which case one of the pins will always just be "not connected". If ERC or DRC complain too much about it, then you can easily duplicate the stock symbol, add a 3rd pin, and set it to no-connect in the schematic.

Sure enough, I forgot about that. The read-before-write info is not in the datasheet though (that I could find), and very easy to forget about. I only ever saw it mentioned as a note in the System Design book TI published. So, I was mistaken. There must be something else going on with your tests.