Has anyone built the Dallas breadboard computer from Art of Electronics? - Page 1
Forum section: electronics / projects

author: SpannersToSparks
author_rank: Regular Contributor
timestamp: April 28, 2018, 10:51:31 pm
content: If so, where did you manage to find all the extra parts not listed in the parts list? I know you can buy one module off the site for like 140 bucks (LCD output module), but there's another part you need (keypad module) that's nowhere to be found. Anyone been able to figure it all out, or better still documented it?Cheers

author: rstofer
author_rank: Super Contributor
timestamp: April 29, 2018, 12:37:30 am
content: I glanced over the project and it seems, well, boring. Sure, you can buy an MCU and hang some memory and such around the edges and get something to work but all the effort is in building, not learning. The custom PCB doesn't seem to be available so you have to extend your own buses over several breadboards. It's doable but there is probably a better project to start with:https://eater.net/8bit/This project is well known and well understood. I suspect it has been duplicated on a number of occasions. This project doesn't use an MCU, it builds one. Sure, you can't program it to solve world hunger but there a lot of learning to do.As pointed on the LtAoE, a lot of people will just buy an MCU development board and call it a day. Well, how about a simple Z80 project that, depending on which kit you pick, can possibly run a full-blown operating system from the '80s - CP/M. You can scour the Internet and find all the goodies. A macro assembler, a PL/I compiler, tons of utilities and so on. I haven't tried to transfer these to my incantation because I have done the same thing on a 50 MHz one-chip Z80 board. I added a Compact Flash, loaded the files (forgot how) and it's off to the races.If I want to know about signals on the bus, no problem, they're all right there. Of course you need a scope to see them because this machine runs at 7 MHz I believe.https://rc2014.co.uk/It uses a PC as the console.There are a number of 8051 development boards on eBayhttps://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR0.TRC0.H0.X8051+trainer.TRS0&_nkw=8051+trainer&_sacat=0I would probably splurge and buy this one:https://www.ebay.com/itm/8051-Microcontroller-Kit/282939936088

author: rdl
author_rank: Super Contributor
timestamp: April 29, 2018, 01:21:35 am
content: Quote from: rstofer on April 29, 2018, 12:37:30 amThat seller has boards for several of the popular older processors. I've been tempted to buy one just to check it out. Their offerings seem to vary over time.https://www.ebay.com/sch/kswichit/m.html

author: SpannersToSparks
author_rank: Regular Contributor
timestamp: April 29, 2018, 09:46:54 am
content: I could try the eater one. That said I wanted to do the aoe as I already bought half the parts. Does anyone know what the Appendix 14N 20 he is referring to on page 620 of the student lab guide is? The keypad module schematic. There isnt such an appendix in the book, and figure 14N 20 refers to a logic gate. The site only sells the LCD module, even though the link name refers to both the LCD and programming module. I think the authors have forgotten about it.Edited due to misunderstanding something in the project

author: rstofer
author_rank: Super Contributor
timestamp: April 29, 2018, 02:47:46 pm
content: I think the Appendices are a work in progress. This seems to come up from time to time.There are so many other ways to build up a breadboard computer that it isn't really all that important to use the one in LTAOE. The Ben Eater project is kind of 'over the top', building up a CPU from low level chips. It would certainly be educational.I need to spend more time with Ben's project. When I saw EEPROMs in the parts list, I thought this might really make the project difficult. The CPU is microprogrammed - an approach to building the control unit that makes CPU design quite approachable. Even mainframes were microcoded. The fact that he has another project using an Arduino to program the EEPROMs makes this CPU project even more interesting.Side note: The original 8" floppy was originally invented to load microcode for the IBM 370 series.Before heading down the rabbit hole of the LTAOE project, I suggest you spend time with Ben's videos. I really think his project has great merit. It certainly gets down to the nitty-gritty of a CPU design.I'm a little light on projects right now, maybe I'll follow along.

author: David1
author_rank: Contributor
timestamp: May 06, 2018, 06:18:44 am
content: Hi SpannersTo Sparks,Did you decide which way you're heading on this? Instead of the LCD module with added functionality I was going to use a Silabs C2 USB programmer plus a USB logic analyser for less than 20 quid all in, following the 8051 path (not Dallas big board, but apparently you can get a Dallas microcontroller programmer cheaply on Ebay too):https://www.ebay.co.uk/itm/272558679897http://hobbycomponents.com/testing/243-hobby-components-usb-8ch-24mhz-8-channel-logic-analyserSo looks like it would get round the LCD but not the keyboard. I've left a message on the LAoE website and Tom Hayes has responded to another message previously so fingers crossed. Having got to Chapter 7, I like the LAoE approach and would prefer to stick with it (and just spent ages building up parts orders for the next 9 chapters) but rstofer's suggestions look interesting and helpful, so I intend to do some research on those.Just wondering if you'd reached a conclusion.https://www.eevblog.com/forum/beginners/learning-the-art-of-electronics-keypad/https://electronics.stackexchange.com/questions/372081/learning-the-art-of-electronics-lcdhttps://www.eevblog.com/forum/beginners/learning-the-art-of-electronics-110413/msg1513984/#msg1513984

author: rstofer
author_rank: Super Contributor
timestamp: May 06, 2018, 06:12:53 pm
content: Check out the other thread of David1'shttps://www.eevblog.com/forum/beginners/learning-the-art-of-electronics-keypad/In reply 9, I proposed a solution to the keypad problem that would use an Arduino (or just the ATmega328) and some port expanders to reproduce the entirety of the keypad board. I really think this is an interesting and elegant solution to the fact that there isn't one iota of design information about the keypad.Note from the photo on page 218, there is more to the keypad than just the pad. There is a two digit display, there is some kind of keypad encoder and some latches along with some dip switches.The CPLD (was probably a PAL at one time) is just the 16 bit preloadable counter. That can be bought from Proto_advantage. Links provided in the other thread.

author: David1
author_rank: Contributor
timestamp: May 07, 2018, 07:25:34 am
content: There's a schematic of the keypad in the old Student Manual (thank you bd139!) at the end of Chapter 15.