VT-100 usb keyboard

[Wesley Baier]

Ive just finished assembling my 8800 experimenter kit, and everything on it seems to be working great except the usb keyboard function. When i set it to load profile 1 on startup the VGA output works great and displays text, but any keyboard ive tried has not worked with it. Ive tried almost every type of keyboard in hopes its just some incompatability issue to no avail. I checked the soldering on the vt100 board and everything looks good on it, and all the connectors to the motherboard are in place and seem to be functioning as they should. Does anybody know what could be wrong?

[Chris Davis]

When you say the VGA output displays text, do you mean more than just the copyright notice?  Because the copyright notice will display simply because power is applied, it's not a sign that the input/output is actually routed through the VT100 emulator.  Here's how to tell: with all address switches down - press AUX1 down.  It should show a list of built-in applicaitons.

If that works, try raising AUX1, you should see "MEMORY SIZE?".  Press enter on the keyboard.  If that works, the keyboard is working.

Watch this video: https://www.youtube.com/watch?v=xINymzBidoE

[Chris Davis]

BTW, that video mentions a PS2 keyboard, the VT100 emulator now uses a USB keyboard.

[Wesley Baier]

Yeah, I've gotten it to display all the built in apps and it runs things like terminal pong and boots into cpm, but the keyboard doesn't function in anything that I've tried so far.

[Chris Davis]

Watch the LED on the VT100 board. It should flash every time it receives (or transmits) data, including when a key is pressed on the keyboard.  What do you mean you've "tried almost every type of keyboard"?  Keyboards most likely to work are very simple USB keyboards with no extra features at all.

https://adwaterandstir.com/2022/02/06/keyboards/

[Wesley Baier]

The keyboard im using now is a wired logitech with no backlight, internal hub, etc, it's as basic as it gets. The activity led on the back of the vt100 board is lit on powerup and stays lit until something displays in the screen, but after the display is done updating it goes back to staying lit. Pressing any key on the keyboard has no effect on the activity light.

[Chris Davis]

The limitation is actually in the VT100 emulator, rather than in the Altair-Duino itself.

The VT100 emulator runs on a fairly small PIC32 microcontroller. Its firmware includes a USB host driver specifically for a standard USB HID keyboard. Unfortunately, USB hubs require an additional USB hub driver and considerably more code/resources. The author of the VT100 firmware determined that there wasn’t enough available memory in the PIC32 to support both the keyboard and hub protocols while still running the terminal emulator.

Because of that, the keyboard has to appear directly to the PIC32 as a USB keyboard.

That means a simple wired USB keyboard will normally work, but a keyboard connected through a USB hub will not. Some more elaborate keyboards — and some wireless keyboard receivers — internally present themselves through a hub or as a composite USB device, which is why compatibility can sometimes be unpredictable even though they work perfectly on a PC.

It isn’t a matter of the Altair-Duino intentionally rejecting hubs; the firmware simply doesn’t contain the USB hub driver necessary to enumerate devices through one.

David Hansel, who wrote the TerminalUSB firmware used in the kit, documents that limitation here:
https://github.com/dhansel/TerminalUSB

I don’t think Logitech keyboards as a brand are a problem. In fact, I found an older post in this group from someone who specifically said the cheapest Logitech USB keyboard they could find worked fine with the VT100 emulator.

From what you’re describing, though, it sounds like the VT100 board may not be recognizing/enumerating that particular keyboard at all. The USB support in the PIC32 firmware is fairly limited — it expects a directly connected standard USB HID keyboard and doesn’t have the more complete USB support you’d find in a PC.

As a test, do you have another plain wired USB keyboard you could try, preferably a different brand? Even a very basic keyboard can sometimes present itself differently over USB, so trying a second keyboard would help determine whether this is a compatibility issue or whether we need to look elsewhere on the VT100 board.

Also, if the keyboard has Num Lock or Caps Lock LEDs, do those respond at all after power-up?

[Wesley Baier]

I have a few older keyboards I've tried and none of them seem to work. Caps/num lock light doesn't respond (on the keyboards with them)

[Chris Davis]

One thing I discovered digging through David's firmware - it explicitly turns Num Lock on when it detects a keyboard has attached.

[Chris Davis]

You could download USBTreeView and paste the text from the top-level of the USB port it is connected to.  Then we could see why it's not working.

[Wesley Baier]

I just tried plugging it in and my computer gave me a warning and said it is drawing too much power. 

[Chris Davis]

When you say you got the "drawing too much power" warning after plugging it in, do you mean when you connected the Altair-Duino's Arduino programming USB port to your computer, or when you plugged the USB keyboard into the VT100 board?

Also, when connecting the Altair-Duino to your computer by USB, please disconnect the external plug-in power supply first. Power the Altair-Duino from the computer's USB connection only, or the power supply only, never both.

Then try this with the USB keyboard disconnected from the VT100 board:

1. Disconnect the Altair-Duino power supply.

2. Disconnect the USB keyboard.

3. Connect only the Arduino programming USB port to the computer.

Does Windows still report that the device is drawing too much power?

If it does, stop there and let me know. That would suggest we may have a power/USB hardware issue rather than simply an incompatible keyboard.

If it does not, then connect the keyboard to the VT100 board while the Altair-Duino is still powered only from USB and let me know whether the warning appears at that point.

[Wesley Baier]

When i plug in the microusb port it shows up fine and i can use it to interact with the machine (play games, load operating systems, etc) using teraterm, and it shows up normally in usb tree view. when i plug the kayboard in nothing seems to change

[Chris Davis]

When you're connected via USB the VT100 emulator is not used at all, so therefore the keyboard is not used.  I'm trying to determine what caused the message about drawing too much power.  

Since you have USBTreeView, paste the full USBTreeView descriptor section from the top level of the port when the keyboard is connected to your Windows machine.  Then at least I can see if the keyboard should work with the VT100 emulator.

[Wesley Baier]

This should be it.

[Chris Davis]

Unfortunately I need all of the information.  I suspect the lines I need to see are immediately below what you sent.

[Wesley Baier]

[Chris Davis]

Thanks, this is very helpful. I don't think your Logitech keyboard itself is the problem.

USBTreeView shows that its primary interface is a standard HID Boot Keyboard: Class 03, Subclass 01, Protocol 01. That's exactly the type of keyboard the VT100 firmware is intended to support. It also only requests 90 mA of USB power, so it is not a particularly high-current keyboard.

In fact, I tested another keyboard that works with the VT100 which is substantially more complicated and advertises up to 500 mA.

So I'm becoming more suspicious of the USB host/power side of the VT100 board.

One thing I'd like to clarify: when Windows gave you the “drawing too much power” warning, exactly what were you plugging in at that moment — the Altair-Duino's programming USB cable into the PC, or the keyboard into the VT100?

If you have a multimeter, I'd also like to know the voltage between +5V and ground at the VT100 USB keyboard connector.

At this point I'd start looking for solder bridges or unsoldered pins on the VT100 emulator board.  Take a look at the last schematic in your manual and check continuity between the USB jack and the PIC32 microprocesor.