RetroChallenge 2019/03

RetroChallenge Updates:

Check out all of my RetroChallenge 2019/03 posts and updates.

RetroChallenge Goals:

• Finalize Apple II+ 128K RAM mods
• Kim-1 simulator for the Apple IIe

Apple IIe Kim-1 Simulator (Kim-2e ?) Summary

I am really excited to finally get to do some work on an Apple IIe KIM-1 simulator. I don't have the money or space for a KIM-1, so this is as close as I am going to get. The end goal will be to have something that can run unmodified KIM-1 software. This will be tricky due to the conflicting address spaces between a KIM-1 and Apple II.
It will basically be a MOS 6532 RIOT IC on an Apple II peripheral card with some logic to enable it at the proper address locations. I will need to use an Apple IIe so that I can disable the built-in RAM at the addresses that KIM-1 software would expect the 6532. This RAM inhibit feature is not available on the Apple II+. I was considering including a ROM, but it will be easier to load the KIM-1 ROM data in Apple II RAM at the correct address. We will see how that works out. I am also considering using Mike Willegal's SuperProto card as a base for this project since the pinouts of the 6532 and 6522 are fairly close.
I don't think I will have time to build the keypad and display, but I may be able to add an RS232 circuit for user input.

Growing collection of Apple II and KIM-1 prototyping parts. 

a2usbdsk not working on Raspberry Pi yet

Although my Apple IIe Platinum was not working correctly, I remembered that the color pattern I was seeing was actually a self-test mode that the Enhanced Apple IIe goes into without a keyboard connected. My keyboard was connected, but was also shattered and seriously damaged. Fortunately, another Apple IIe keyboard saved the day.

Unfortunately, a2usbdsk on the Raspberry Pi is not able to send data fast enough for the Apple IIe to read... yet. I have some code optimizations I need to test out which I think may help the situation. That said, even my old MacBook air was barely able to keep up. My newer 1.8 GHz dual-core Intel Core i5 MacBook Air seems to have no problem. I'll keep trying this weekend.

Update!

The Raspberry Pi is able to keep up! The problem is that the FT232H is stalling very often. I had this problem early on in the development of a2usbdsk on Mac OS X, but I worked around it by writing most of my own read/write loops and avoiding libmpsse for the most part. There must be some difference in how libusb or libftdi is handling the packets on the two operating systems. By frequently purging the buffers, I was able to get a disk to load! Need to find a better solution though. More testing should narrow down the problem.

a2usbdsk ported to Raspberry Pi

I was able to port a2usbdsk to the Raspberry Pi quite easily due to it being based on libusb and libftdi. Really, I just had to set up a makefile. I had some issues getting it to open the FT232H though. libmpsse does not return any errors when attempting to open an FTDI device. This makes troubleshooting very difficult and frustrating. After adding some logging, I determined that the libftdi function ftdi_usb_open_desc_index() was returning error code -8, "get product description failed". Getting the product description is a pretty simple function and that error was not appearing on Mac OS X, so it left me baffled for a while. In the end, the issue was that Raspberry Pi/Linux strictly controls who can access USB devices. "sudo" got it running, but setting up a udev rule seems to be a better solution.

I have not tested this with a real Apple II yet, as my Platinum Apple //e was pretty much destroyed in a recent car accident due to air bag deployment. The case is shattered, but it may still work. I'll try this weekend.

RetroChallenge 2013WW Review

This has been a fun month. I am really excited that I completed one project and hopefully provided a useful tool to the Apple II community.

Disk ][ Emulator: I just uploaded the USB AII-SPI-DSK executable and schematic. The binary is compiled for x86_64.

AII-SPI-DSK project source code is now available too. The code requires user to have libusb, libftdi and libmpsse already compiled and installed. Once you get past the Xcode project format, the code should be pretty portable to other platforms. Most of the coding was done fast and dirty, so please excuse the unavoidable errors.

The USB AII_SPI_DSK Disk ][ Emulator is by far my most complex electronics project I have ever taken on. Fortunately, the Apple Disk ][ controller card is pretty flexible with the input it can take, or I would have never completed this.

I didn't quite reach my lofty goals on this project, but I did end up with a good proof of concept and a handy device in its own right. And, because this project uses a standard SPI stream, I should be able to easily create a micro-controller based solution that actually uses an SD card! The Retro icing on the cake for this project is using 2 ICs recycled from an old Apple II+ for my build.

Apple IIe Platinum: Living a new dust-free life.

Apple IIGS: Still rusty and in pieces. A little closer to living though.

Apple //c: Still neglected with 255 ROMS. I didn't even get to think about this project.

Take a minute to check out the RetroChallenge website and see what the other participants worked on.

First IIe Challenge Completed!

] PRINT "HAPPY NEW YEAR!"
For the first day of the Retrochallenge, I tackled what appeared to be the easiest project: getting my latest purchase, an Apple IIe Platinum, up and running. With the help of my air compressor and a clean paint brush, I managed to get all of the dust out of it. I booted 'er up and was greeted with Apple //e at the top of the screen! However, Control-Reset was not giving me an Applesoft BASIC prompt. I pulled the floppy disk controller card, rebooted and got a prompt, but I still couldn't reset the computer. I narrowed the problem down to a bad Reset key which looked bent out of whack to begin with. Some continuity testing showed that the key was not making contact. So: disassemble computer, de-solder, disassemble key, straighten the bent contacts until the key works, re-assemble key, solder it in, re-assemble computer. I replaced about five missing screws on the keyboard too. It looks like a previous owner tried to fix it and left the screws out. This was putting stress on the solder joints of the keys. I also managed to dig up a platinum Apple Mouse to match the computer and connect to the Mouse Interface card. Anyway, she works! Success on the first day!? Maybe I should stop while I am ahead...

Key removed - note missing screw for brass standoff	Key soldered in with new screws
No more dust- much better!	Target Environment: Apple IIe, solderless breadboard, Disk Interface card, FTDI UM232H or Arduino Nano?, 74LS series ICs

Another Challenge

Add another challenge for me.  Since I expect to be working on both my Apple IIs to fix them up, I wanted to get one that I could just work on to develop the disk emulator project. I picked up a Apple IIe platinum from a guy on craigslist who is developing an app to "reinvent classified listings." It looks like it is in decent shape, but is very dusty and is missing a few keys. Hopefully, it will be easy to get it clean and running.