New build and an expansion port question

[Matthew Brugman]

Hi,

I finished the assembly of my 8800 Experimenter Monday and have been enjoying it quite a bit!  I verified all functionality; the RS-232 serial, the VT100 emulator, expansion bus, etc.  I even wired in the TX/RX serial port and have that working  ( I used a Bus Pirate to do the low-level serial to the TX/RX pair ).

Now for my expansion port question:

Has anyone created a "prototyping" expansion card?  What I mean by that is:

• A "standard" size expansion card
• Pre-populated (and routed) with:
  • Shrouded bus connector
  • Logic for address decoding (CD4068BE, 74HC04, 74CH00, jumper headers, etc.
• The remainder of the board with unconnected vias on a .1" grid; think of a protoboard/stripboard kind of thing
• A "bus" of vias for ground, +5, +3.3, etc.

The idea is that a person (me! haha) could use it to develop and prototype new expansion cards.  

If there is something like this already around, can anyone point me to a project (or at least gerbers)?  If not, then I can start working on something.  I just don't want to waste my time duplicating existing work.

Thanks much!  (and thanks for a fun kit to work with)

Matt

[Cliff Chism]

I haven’t seen anything like that in my travels. Looking at Hansel’s repos, (https://github.com/dhansel/Altair8800-IOBus) I dont see anything like that, although I’d be interested in it as well. Maybe Chris has something?

 I’m also interested in what you did with the bus pirate and I’m about to undertake adding the esp01 to my experimenter using rx/tx lights on the due. I do have a bus pirate, but not sure why it might be useful in the situation. I have a lot to learn…

Unless someone else knows something, you’ve probably got yourself a project. Might I suggest trying a 10/100 ethernet expansion card? Fwiw, im not sure it’s even possible. I’m still very early in my Altair journey.

[Matthew Brugman]

@Cliff - in your case, the Bus Pirate can help verify your wiring and setup before you plug in the esp01.  Maybe help find issues before they arise :)

You'll need 4 wires from the Altair: 3.3V, GND, TX, and RX.  With power off to both Altair and BP, connect them up this way:

ALTAIR   BUS PIRATE

-------  ----------

 3.3V     Power in

 GND      GND

 TX       RX

 RX       TX

Then this sequence:

1. Plug Bus pirate into your computer USB
   1. Open the BP in a serial console (whatever works for your OS; I typically use minicom)
   2. Bus Pirate will be in HiZ (high impedance) mode
2. Power on Altair
3. Set BP into UART mode
   1. M  <enter>
   2. Select UART
   3. Configure serial (whatever esp01 uses, 9600 8N1?)
   4. P <enter>   This will enable the internal pull-up resistors
   5. Do not enable the power supply of the BP!!
   6. Put BP into UART bridge mode
      1. BP version 5 or 6: type "bridge" <enter> (no quotes)
      2. BP version 3:  "(03)" <enter>. (no quotes)
4. Put Altair into config mode
   1. Set up the TX/RX serial port (again, 9600 8N1?)
   2. When you select TX/RX as the host serial port, you should see messages start appearing on the serial console on your computer for the BP. You'll have to hit "Y" and <enter> so the Altair config knows that it's a valid interface.  If you don't see the messages, try reversing TX/RX.
   3. Save it as a new config to be selected on power-up

At least that's what I did, lol.  Anyway, if you do all of that, then you know that your soldering was good and that everything up to the esp01 is working.  Also, I left the LEDs on the Due; I thought they would give me the pull-up for serial, but I still had to add them to get logic level serial to work.

On my Experimenter, I added headers for the esp01 and serial selection jumpers.  I had planned on using Dupont-style wires to get 3.3, gnd, tx, & rx for my serial device, but then the back wouldn't fit because of interference with the VT100 board.  I ended up soldering wires to the pins and leading them out the opening for the expansion bus:

The green and blue wires at JP5 are small gauge coming from the TX/RX LEDs on the Due, the other 4 go "outside" to whatever serial device I am hooking up.  My plan is to construct my own version of the esp01 with parts I already have.  I plan on sharing that project when I get it done.

One final note - if you are using a BP version 5 or 6, there's are great docs at https://docs.buspirate.com/docs/overview/hardware/ and an active user community at https://forum.buspirate.com .  (disclaimer - I'm a minor contributor to that project and active on the forums).  The BP 3 is deprecated, but there is information available online.

[Cliff Chism]

Thank you for taking the time to type all that out. It is useful to me and appreciated. My bus pirate is a bp3.

[da...@hansels.net]

There is currently no (official) prototyping card as you describe it - unless someone else has made one that I don't know of.

However, there is a card that lets you build a software-defined device. The bus monitor card basically directly
connects a Raspberry Pi Pico to the expansion bus. That means that by programming the PiPico you can
implement any card in software, without any other soldering. As an example, there is a 88-SIO implementation 
(as opposed to the existing 88-2SIO card) included in the bus monitor description.

David

[Matthew Brugman]

I did see that card, it definitely looks great for debugging and development. 

I think I’ll move ahead with my idea, too. The idea of wire wrapping in the “proto” area appeals to me ☺️