ASCII Video Terminal

[ceyde]

I have been having fun with my new toy hooked up to a laptop,

But I really wanted a "Real" stand alone video terminal for s full retro experience, 

looking around ebay for a old terminal was frustrating,

Since I had some older lcd monitors lying around I thought I might build one of these  http://geoffg.net/terminal.html

After a little trial and error (ie learning curve) It's working!

Since it's 3.3V it's connected directly to AltairDuino circuit board (no MAX232 used)

Total build cost was under $30

Here are some photo's

[Colin Little]

Looks very good and I am encouraged by your build. Picture quality looks good. I have all the parts now to build mine as well. I didn't have the pcb though so it's back to strip board!! Hope to complete it by weekend.

Colin

[Tom Lake]

I bought one and assembled it last night. It went together very easily. My video output (to an LCD monitor) doesn't look too good, though. Characters have rough edges. All-in all, it's a worthwhile build! I have mine connected to an Altair Clone. When connecting to the AltairDuino, do Rx and Tx go to corresponding pins on the terminal board or do you have to cross them?

[Tom Lake]

I wish I could edit my posts after I send them! I see you have wires coming from the place on the board where the PS/2 connector normally goes. What do you have in place of the PS/2 connector?

[ceyde]

The ps/2 connector I ordered came with wires on it, so I connected the wires to the pcb

[Pete Roemer]

Hi Tom -- sounds like a fun project... where did you buy the kit?

Pete

[Tom Lake]

It's not a complete kit but I bought the PCB and programmed PIC chip from Silicon Chip , an Austrailian magazine. I got the rest of the parts from Digi-Key, Mouser Electronics and Jaycar. The composite connector is particularly hard to find since the mounting holes don't seem to be standard. I found that at Jaycar. A complete parts list is in the article and on the author's website: Geoff's Projects.

[Ed Thierbach]

I have the PCB on order, but got rather frustrated trying to order the parts.  I expected (unreasonably, I guess) that I could order them all from one source.  Tom, would you have the part numbers handy from Jaycar, DigiKey and Mouser?  If I have to order from three places, I can at least get the right stuff. :-)  But please don't go to much trouble; now that I know the Jaycar secret I can make it through ordering the parts.

-Ed-

[Tom Lake]

1. 1 USB B Type Socket PCB mounting                                               Jaycar PS-0920
2. 1 DE-15 (or HD-15) High Density 15 Pin Female D Connector        DigiKey A35116-ND  
   
3. 1 RCA Socket PCB mounting                                                           Jaycar PS0279
   
4. 1 6 Pin Mini DIN Female Connector (socket) PCB mounting           Mouser 806-KMDGX-6S-BS 
   
5. 1 28 pin SDIP IC Socket                                           From my Parts box (Make sure NOT to get a DIP socket. SDIP is much narrower.)
   
6. 1 8MHz Crystal                                                                                 Mouser 815-ABLS-8.0M-T                  
   
7. 1 4 way Header Connector (male), PCB mount , 0.1 inch pitch       DigiKey A19431-ND
   
8. 1 2 way Header Connector (male), PCB mount , 0.1 inch pitch       DigiKey A1921-ND
   
9. 10 Header pins, 0.1 inch pitch                                                          DigiKey S9337-ND   
10. Microchip MCP1700-3302E/TO voltage regulator (IC2)                   Mouser 579-MCP1700-3302E/TO
11. 1 Red LED, 3mm                                                                              DigiKey 516-1791-2-ND
12. 2 27pF Ceramic capacitor                                                                Mouser 594-S270K25SL0N63L6R                                                        
13. 2 100nF Monolithic capacitor  (Actually 0.1uF)                                Mouser 81-RDER71H104K0S1H3A          
    
14. 3 10μF 16V Tantalum capacitor                                                       Mouser 581-TAP106K016SCS
    
15. 1 82Ω resistor                 I got these on eBay since parts houses need you to order 5000 at a time.
    
16. 1 150Ω   "                                                                                         Mouser 588-OK1515E-R52
    
17. 1 220Ω* "                                                                                          Mouser 588-OK2215E-R52
    
18. 1 470Ω  "                                                                                          DigiKey CF14JT470RTR-ND 
    
19. 4 4.7KΩ "                                                                                          DigiKey CF14JT4K70TR-ND
20. 1 10KΩ                                                                                             Mouser 603-MFR-25FTF52-10K
21. 1 100KΩ                                                                                           Mouser 603-CFR-25JT-52-100K

[Ed Thierbach]

Thank you so much, Tom! The part numbers will be most helpful.

[Tom Lake]

If anyone has trouble finding a reasonable quantity of 82Ω resistors, pm me a mailing address and I'll send you one. I ordered a hundred and only need one. 

[Pete Roemer]

Thanks, Tom!

Pete

[Chris Davis]

Holy cow, that's cool!  I should build that into the Altair-duino!  Yes or no?

[Randy]

Personally, I would vote YES.

[Tom Lake]

Yes! If you have the real estate to add the chip and its support resistors and capacitors, why not?

[Pete Roemer]

I would sure be interested in an "upgrade" kit add on of this terminal circuit for my current Altair-duino.

Pete

[Randy]

As Tom mentioned, there may be an issue of available free space. If this does NOT fit directly, it should be possible to redesign the board. Maybe as a double stacked 2-board solution? (possibly with off-board/panel mount VGA-PS/2 connectors via IDC ribbon cables?)

[ceyde]

TX to TX and RX to RX

also FYI it takes it's power off the AltairDuino, no need for a separate USB power supply for the terminal.

[Chris Davis]

I'm thinking of a "daughter board" that sits perpendicular to the main board with two serial ports, power, audio jack, keyboard, and VGA port.  Then it could be installed as an "upgrade" to the currently built kits.

[Pete Roemer]

Sounds perfect to me.   Where do I sign up?

Pete

[Jim McClanahan]

Sounds like it would add just about anything people have mentioned wanting. (With the possible exception of a cassette interface (which could be built separately and fed with a serial line) and a "built in" video card (which would take some significant hardware and software changes).)

One thing I like about Geoff's PIC-based design for a serial terminal is that it allows a "daisy chain" serial connection. So if you had it attached but didn't want to use it, you could just attach any other serial device and it would simply pass the serial data through in both directions.

From a design perspective, I'd been thinking of using a "shield" board that sandwiched between the Arduino and the front panel. I was just going to use one of the proto boards that is available, but if you designed one that had some extra real estate you could build the serial adapter on it. A shield card would be easy to install, let you tap into the line for audio and let you insert 1K resistors in the PROTECT lines (for current limiting) as well as pick them off for a serial connection (maybe with jumpers that selected what you wanted to use those two lines for). With a bit of work, you could also bring up the lines from the removed RX and TX LEDs to a plug if you wanted.

To me, the big advantage of a shield of this type would be that you could design it so that any pin could be passed through, tapped, or routed off (or something in series or for another use) to the board. That could leave some flexibility for future features and additions.

Thanks,

Jim

[David Hansel]

Regarding a cassette interface, I believe that Mike Douglas' cassette interface for the Altair clone should
also work with the Altairduino. According to the schematics the connections on the emulator side are
just 3.3V, GND, serial TX and RX. All it does is to convert a regular serial signal to audio signal and back,
so that should work just fine - I say should because I haven't tried it and I'm not sure if I will ever get to it.

That interface also includes a MAX232 converter which it feeds through to the serial port on the emulator
whenever the cassette inputs/outputs are not in use.

[Jim McClanahan]

Just to be clear, I had my share of using cassettes back in the 1980s. :-)

And there seems to be a shortage looming:

http://theweek.com/speedreads/735269/america-running-cassette-tape

Jim

[David Hansel]

I hear ya - lots of memories of using my C64 with a home-made adapter to attach a
regular (non-commodore) cassette recorder. Don't really have to go through that again
on a different system.

[Tom Lake]

Yeah but back in the old days, cassettes were a hit and miss affair. I had a TRS-80 and spent a lot of time fiddling with cleaning and realigning tape heads and adjusting the volume control and still had to try several times to load some system tapes. Douglas' cassette interface board has been 100% reliable for me. Calibration consists of one volume adjustment for all tapes. Even 40 year old tapes load the first time. For those who really want the 1975 experience of owning a new Altair, there's nothing like it. Build the ASCII serial terminal (no PC terminal emulators allowed!), hook up a cassette interface and you have an authentic nostalgia-fest.

[ceyde]

I'm building another one!! but I had a few extra PCB's made.

If anyone wants one,  I can mail one to you (US address only) for $7 each (covers postage and the prorated cost of the PCB)

Email me if your interested.

[Tom Lake]

To all Altair-Duino users: I ordered a bunch of composite RCA sockets (the yellow component in the ASCII Terminal pictures) It's hard to find ones that fit perfectly but these do. I you can't find one that works, pm me and I'll send one to you.

[Randy]

Ceyde,

I would like to buy one of your boards.

Randy

[Randy]

Tom,

I would appreciate one of the RCA connectors.

Randy

[ceyde]

Randy if you paypal me Corne...@yahoo.com and email your address I will get it right out

[Randy]

Ok, well...

Since I now have a PCB on the way, will imminently have an RCA connector, and have a PIC programmer, I might as well start making a shopping list for Digikey or Mouser.

Does anyone out there need a programmed Microchip PIC32MX250F128B-I/SP for this project? I'd be happy to order extras and send them out for cost of materials and shipping. (USA Only at this time, but could probably be convinced to send elsewhere. That being said, it might be cheaper to just buy a programmer off of eBay depending on what the shipping costs to South Africa or Colombia turn out to be. I got my programmer with the ZIF socket board and cables for $21 USD delivered.)

[Tom Lake]

If you don't send me a mailing address, how can I send you an RCA connector? :)

[Randy]

Email sent.

This Google Group is linked to my work email. I don't usually check my work email on the weekend. As such, I didn't see the email.

Thanks, Randy

[Randy]

Received PCB mount RCA Jack from Tom Lake, Check! (Thank You.)
Received PCB from ceyde, Check! (Thank You as well.)
Waiting on quite a few packages from China and other locations with assorted numbers of many small parts that I don't have in my junk boxes. Check! (is in the mail.)

Randy

[Jim McClanahan]

Tom, if you have any spare RCA connector's left, I'd appreciate one. I have about a half dozen styles of them I've scavenged from old gear over the years and none fit. :-(

I have the circuit board, the PIC (plan to program it later today) and all of the other parts except the USB and VGA sockets.

Thanks,

Jim

[Tom Lake]

I have plenty! Just pm me a mailing address and it'll be on its way.

[Randy]

I emailed Geoff concerning a discrepancy in the PCB silk screen when compared to the published parts list. I will paste his response below.

"There are two resistors that are wrong compared to the PCB silk screen.  They should be 10K and 100K (see image below).  So the schematic is correct.

If you are just using 3.3V TTL signals you can replace the 10K with a wire link.

Hopefully this image will remove any confusion.

The original values worked OK on my breadboard but after I built a few prototypes it became obvious that they created marginal logic levels.  Hence the change.

Geoff"

The silk screen shows 4.7k and 47k, while the updated and correct values should be 10k and 100k.

I hope this info will help others in the group with their project.

Randy

[Tom Devine]

Really good info to know!  I've gotten a PCB and a few of the smaller parts, but have yet to finish the build.  Thanks Randy!

[Tom Lake]

I bought one at the end of October from Silicon Chip magazine in Australia. The silk screen had the correct values of 10k and 100k respectively. Did you order directly from Geoff?

[Randy]

I bought it from ceyde in this thread. I guess his board vendor still has the old artwork.

Randy