My fascination with PCMCIA cards was created out of “necessity”. Most of my retro computing interest revolves around networking, and I wanted something that could natively attach to modern Wifi networks without the need to maintain an old linksys router just for my retro computers. There are many ways to do this, I just wanted something as clean and compact as possible. I was also left out of being able to use the various ESP based wifi modems as I mainly use an IBM PC110 and it has no serial port without a dock.
At the start I looked at butchering existing ethernet cards and wiring in a wifi232 module coupling together the ethernet PHYs. This was very sketchy and the module was large, no real hope of scaling it down.
I quickly moved onto attempting to make my own entire card. I used a small GAL for some address decoding, a parallel UART chip and a flash chip along side the esp8266. This worked quite well and depending on the crystal selected, when having the divisor at 0 (usually 115200 baud) it would actually be 460800. It was quite feasible to fit this onto a board in a tiny case, but the speed limitations and it only being a serial interface always had me thinking about an ethernet interface instead of or in addition to the UART. I did play with SLIP and various ways to use the serial interface to get onto the LAN, but it was not fast enough or transparent enough for what I wanted.
I came back to trying to emulate an NE2000 card on the ESP8266 (also tried ESP32). It was just too slow though, the interrupt latency on the ESP was already almost my entire 12uS time limit for an I/O cycle, and because of the limited IO on the all the ESP’s I needed to use an I/O expander chip or external multiplexer, and in both cases it was just so slow there was no chance. I even played with using a dual-port sram to act as a place to store the CIS on boot and to simulate the registers but there was just no overcoming how slow the ESP was in handling interrupts and manipulating the external multiplexer or expander. Maybe there were some other approaches but I put this back on to the back burner.
Then I saw the work by Ian Scott on the PicoGUS that was using a Rasberry Pi Pico to talk to an ISA bus. This brought the Pico to my attention and I quickly connected one to the PCMCIA bus to play around. I quickly saw that the interrupt latency for the PIO was very low, and the PIO itself allowed some very fast and easy coordination of the I/O wait signals and other potential multiplexing and that is how I arrived where I am at now.
It is a very simple design. I use a CPLD to handle some of the “glue logic”, and to deal with the multiplexing, and it has the added benefit of having 3.3V I/O which is compatible with the Pico, but the I/O is also 5V tolerant which is compatible with the PCMCIA bus.
Next steps, I would like to encapsulate it into a card much like the legacy wifi cards. There will be some bonus functionality available through the USB port operating in host mode.
And depending on mechanical limitations perhaps an audio jack. That may get left to a larger version of the card with more functionality in the future. With the Pico there are so many possibilities.
I am a few months late updating my website on this. I designed a prototype board and assembled a prototype board and completed the switchover to a CPLD. Current status I partnered with somebody that specializes in this kind of thing to complete the analog audio design and sort out various details to make it manufacturable. I hope to have more updates on this soon. Below is a video demonstrating the DMA emulation in action, protected mode games and all.
I have not posted anything about this recently, this is one of the other projects I have been playing with. The goal is to create a PCMCIA soundcard that has the following featureset:
Yamaha OPL3 on the expected 388h address (this is done and working)
MPU-401 with full intelligent mode on the expected 330h (this is done and working)
Onboard Dream.fr wavetable general midi chip connected to the output of the MPU-401 (tested and working)
Option to disable onboard wavetable and only use external midi dongle
Gameport on the expected 200h – 207h (working but needs to be optional to enable/disable).
Digital audio via fully soundblaster compatible interface.
There are very few cards that ever existed that provided SoundBlaster support (IBM 3D Sound PCMCIA), and they are near impossible to find for purchase, so it lead me down the path to make one.
The learning curve has been steep as this project covers multiple areas all of which I was unfamiliar with at the start (and am now slightly familiar with). I got a general proof of concept working pretty quickly but spent too much time playing with wav files and large transfers (i.e. sbdiag tada.wav).
My recent reworking of how I was hooking interrupts solved some other issues I was having with protected mode games so I started to do some better testing on Doom,Duke3D etc and this is when I came to realize that they only use 4k or smaller buffers and the actual transfers are 128 bytes or 256 bytes per autoinit cycle. This totally makes sense given the realtime nature of sound effects during unpredictable gameplay.
I currently refill the 4K DSP every time it drops below half-full. This is not going to work. So I need to think about a better way to handle this.
I was avoiding modifying the DSP code, but for no good reason really. I think it is time I modify the DSP code so that my TSR can have complete visibility into how many bytes are being expected during autoinit mode. I am going to think about it a bit.
I am still alive and working on the project, mainly I have been messing around with this idea for the keyboard light, and generally just trying to optimize the 3D model for the bezel.
Something I have noticed is that I can hear a slight buzz from the onboard speaker and headphones when volume is turned up to full and no sound is playing which is most likely originating from the DC-DC converters. I am going to look into that some more and try to cancel that out with some better filtering on the power supply side of things. It seems that even an unmodified PC110 has this noise when the volume is turned all the way up, even with no inverter connected at all.
The BIOS patch is about ready, it works properly I have just been working on proper safeguards (making sure on a/c power and battery is charged etc).
Here is the current revision of the board. I was not paying attention and I ran those traces too close to that mounting hole, not a major issue as the screw goes into plastic and is not tight enough to damage the solder mask, but still not proper I will move it. DC-DC converts of course are on the back as seen in some other photos.
Here is the keyboard light in action, on one of them is working as I broke the other one and I was lazy to deal with it. Maybe only one LED is needed (if any really).
And here is the 3D printed bezel poorly painted just to see if it would block the light (it does). Feels strange without the IBM logo.
And here are just some random pictures working of 3D model progress.