First, we’re watching the TV a lot hoping for the best for Florida. My family enjoys vacationing each year in Marco Island, which seems to be exactly where Irma is heading. A number of our friends got out of the state in time so we’re hoping they’ll be able to return home to find little damage.
Next week my son goes to college which means I’ll be pretty much gone all next weekend and most likely doing final preparations this week during the evenings. There might be little accomplished here for the next week in terms of Corsham Tech projects but I will do my best to answer emails.
VCF Midwest (just west of Chicago) is happening this weekend. Normally I’d be there but my new full-time job is keeping me busy and I just didn’t want to miss a couple days of work. Yes, I really enjoy what I do for a full-time job, which is writing embedded software.
KIM Clone status… I spent the last two weeks chasing a “software” problem and the finally realizing last night that my design was right for a 6502 but had a slight error for using a 65C02. Once the fix was applied the 65C02 worked perfectly. The design has been updated to accommodate either chip. My plan is to ship with a 65C02 but all of my code is written for the 6502 so it will work with either chip. There is one annoying problem that I know how to fix but just didn’t have time yet to address: the FT232RL backfeeds power into the main circuit, and it’ll take a couple more surface mount parts to fix. The other outstanding hardware problem is that single step doesn’t work; it appears that a single jumper might fix it.
That’s enough for now… there is work to be done!
The KIM Clone is working nicely with the SD card system but a few small problems were found and are being addressed. One was simply a matter of needing 74HCT parts for some of the address decoding. Now I’m working on smaller issues, mostly software but at least two hardware issues. A RAM test was running for about 24 hours without errors and I leave the KIM Clone running most of the day, all day, giving me a lot of confidence that it’s stable. For those in the engineering business, we know that endurance testing is always a big deal, and getting through a long run time is very satisfying.
This is the latest set of pictures from this evening. The KIM Clone rev 1A board is functional and fun to play with! I had Lunar Lander from The First Book of KIM loading, which explains the “SAFE 03” message (I landed my spaceship at a speed of 3). The connector labeled “SD SYSTEM” and U9 are for connecting one of our SD Card Systems. Paper tape and cassette storage was state-of-the-art in the 70s, but now we can use a micro SD to save/load programs to the KIM Clone.
Here are some more detailed photos of specific parts. First is the display and keypad. Those are real keycaps and the keys “click” when you press them so there is tactile feedback when you press a button. The labels on the keycaps aren’t quite good enough but I priced getting custom labels done and it was a $600 investment. For labels. Right now I’m looking at other options. Oh, the big red button is RESET.
The board can take either a 6502 or 65C02. Not sure which I’ll include, but probably the C02. Beneath it is the RAM, the expansion EEPROM and the KIM monitor EPROM. On the left are the power plug and power switch. The system will include the power supply, and it’s rated for 110-220 VAC so it’ll work in most other countries. You can see the SST switch is missing; testing single-step is on the to-do list for this weekend. The expansion EEPROM resides from E000 to FFFF and can be displayed and replaced with RAM. The monitor EPROM contains the modified KIM monitor that resides from 1800 to 1FFF. Either of these EPROMs can be replaced with user-supplied code. The board has a lot of discrete 7400 series parts; a future version might go with a CPLD which can also offer some interesting memory management options. The RAM is 128K but only the bottom 64K is used for now.
There is a USB “B” connector on the top for connection to a PC/Mac/whatever for use as a console. I should probably solder in the two resistors and LEDs that indicate serial port activity. The interface chip is a high quality FTDI part, not one of those “Horrific” chips. The interface is powered from the USB port so the serial port doesn’t go away when the board is powered off. I’m considering going to a micro USB connector but this is working so that eliminates more unknowns for the next spin.
The first public showing won’t be until VCF East in the spring of 2018. I can’t make VCF MW this year. A few people have suggested some additions, and I want to move some of the LEDs around a bit so there will be at least one more revision of the board before it’s ready for sale.