Looking to add USB\PS2 Keyboard to an A500 Tower

ljmarent · May 28th 2021

Hello,

I'm stuffing an A500 rev 5 with ACE2b, Indivision ECS, ACA500plus, ACA1221lc, Checkmate A1500 ATX & Zorro 2 slot adapter and rear plate into a generic ATX tower case.

Will likely add ZZ9000 and faster accelerator card ... down the road.

The piece I'm missing is a quality adapter for a USB or PS\2 keyboard.

I know about a cheap one on eBay, but I've bought from that vendor once before.

I bought their USB adapter for a C64 mouse.

Not only did the product fail to work correctly, I sent a video showing the issues (jumping in one axis), but the vendor choose not to respond at all.

eBay refunded, and I wasn't out any money, but what a tremendous waste of time.

Which is why I'm skipping an otherwise 'perfect' sounding product and continuing to search.

Looks like another option for me might be a Lyra 3

When I examine the big box Amiga keyboard connectors, I don't see a reset signal pin defined on the connector.

I'd like to know if the Lyra 3 generates a physical reset signal on CTRL-Amiga-Amiga that I can route to the A500 keyboard connector ?

When I look at the online documentation...it's honestly 'ambiguous' as to how it's going to perform a physical reset.

http://wiki.icomp.de/wiki/Lyra_3#F9:_configure_TICK_pin

I can re-direct the A500's keyboard connector to a DIN connector on the rear of the case and re-pin the signals as required,

I just don't know what that pinout should be to make the Lyra 3 happy, and if it will supply the physical reset signal ?

Jens · May 28th 2021

Quote from ljmarent

I'd like to know if the Lyra 3 generates a physical reset signal on CTRL-Amiga-Amiga that I can route to the A500 keyboard connector ?

The "big box" version doesn't, but the A1200 version does. However, the A1200 version will not work on your A500, because it is designed to co-exist with a second keyboard on the 2-wire bus (which isn't really a bus!), and with that missing, the A1200 version will not even get to a point where it initializes the PS2 keyboard.

I've had an A500 version of Lyra on my todo-list forever. I even made circuit boards and purchased parts, because the idea was to make a product with two use-cases: One use case would be Lyra for A500, and the other would be something that plugs in between the A500 keyboard and the main board that "sniffs" the communication for certain key combinations to allow switching Kickstarts, a boot selector and the like - this would avoid drilling holes into the case for switches.

Never got around to making this design, and I can't say if I can make room for that in my packed schedule this year.

Quote from ljmarent

When I look at the online documentation...it's honestly 'ambiguous' as to how it's going to perform a physical reset.

http://wiki.icomp.de/wiki/Lyra_3#F9:_configure_TICK_pin

You've found the pin that I have used for the A1200 version's reset signal However, the A1200 firmware does not work on the BigBox version for the reason I explained above: It will wait for the Amiga keyboard to start up and do it's power-up message thing, and only then access the keyboard communication lines.

Quote from ljmarent

I can re-direct the A500's keyboard connector to a DIN connector on the rear of the case and re-pin the signals as required,

I just don't know what that pinout should be to make the Lyra 3 happy, and if it will supply the physical reset signal ?

I'm happy to supply the pinout of the circuit board if you can't figure that out: GND/VCC should be obvious, and clock/data can be swapped until it works. If these are swapped, nothing will break, as the signals are open-drain. The BigBox version will not supply a physical reset signal on a separate pin. Your best chance is to use the BigBox version and make a small circuit that checks the KB_CLK line: When that's "low" long enough, you pull on the reset line. Such a circuit can be copied from the A1000 schematics, for example - a simple op-amp circuit.

ljmarent · May 30th 2021

Okay, I'm ordering the Lyra 3 big box version.

I appreciate the info and push in the right direction on how to add the reset interpreter on my own.
A little extra reading and I just need to monitor the KB_CLK signal for a 450ms+ active low state, and then pull the A500 RESET line low for 100ms.

I'm not going to dig out my year one university analog circuit theory book to play with an OP-AMP, as time and voltage are perfect for an MCU.

I can even monitor the KB_DAT line, to capture the power-up key stream, for option switches.

I don't even need to spin a PCB, just use an Arduino micro in a 3D printed shell with 10K resistors on the KB_DAT and KB_CLK signals and an NUD3105 to pull the RESET signal low.

I can always make it a 'pretty' PCB later.

And I can use the remaining MCU pins for fan speed control, temperature monitoring, RGB, whatever else the tower case might demand down the road.

Cheap and cheerful sub $2 solution for adding reset circuit to an A500.

Thank you,

Jens · May 31st 2021

Quote from ljmarent

I can even monitor the KB_DAT line, to capture the power-up key stream, for option switches.

Caution: Lyra does not send the power-up key stream. Most PS2 keyboards fail their self-test if a key is pressed during power-up, so I didn't bother to implement that.

Quote from ljmarent

and an NUD3105 to pull the RESET signal low.

You can even skip on that, as most micro controllers allow programming output pins as open-drain or quasi-bidirectional. No need for an extra driver.