I've been working on a project off and on for about a year to replicate the original Apple 1. It's a SBC computer with a 6502 1 MHz, 32K SRAM, 8K EEPROM, 6821 PIA and 40 X 24 video terminal output. A friend of mine helped me design a 3 chip video terminal using an Atmel AVR microcontroller. I've had a lot of people ask me why I didn't make it 100% look like the original. Well, some IC's are nearly impossible to get and I wasn't out to make a look alike, just function alike. The I/O is a 6821 PIA like Woz used in the Apple 1 with the addressing being at $D000. The ram is at $0000-$7FFF and the EEPROM is at $E000-$FFFF. I was going to make just one for myself since I could never afford a real Apple 1, but I've had requests to make boards for other people, so I'm going to run a small batch off. Right now we're finishing up the video firmware revision but it all there and works with Woz's original monitor.

Tell me what you think.

Vince
http://home.comcast.net/~vbriel/apple1.htm

Vince,

Your project looks interesting. Of note is the video display. I know several readers here have expressed an interest in having an inexpensive, low parts count video display for their projects (me included). Purhaps you and/or Greg can make that portion of the design available.

(See the Video Output topic in the Hardware section of this forum)

Let us know when you are done and have an estimate on the board cost.

Thanks!

Daryl

Daryl,

I checked out your site, nice work, especially the video section your designing. I have questions but I'll email you later about it. I think its easy to designing ram, rom, I/O devices for the 8-bits, but video was all greek to me. I tried some things but could never get the dumb timing down right and it has to be perfect. This is why I asked for help from my friend Greg. He's a hardware and software engineer and he said he could come up with a down and dirty solution for video text.

I read where people are interested in video for their projects. The main IC used is an AVR ATMEGA8 microcontroller which handles all processing of the incoming ascii data. 7 bits incoming from your I/O device is converted into ascii then sent to the composite out on the screen. the display works as follows:

Screen starts at lower left corner. As characters are received the cursor automatically moves over to the right one space. Upon a character return CR the screen scrolls up one line and the cursor moves back to the left. The cursor is only available at the lower line on the screen. This keeps with woz's Apple 1 design. There is no X,Y placement on the screen. There are a total of 2 control lines. RDA and DA. RDA states that the video controller is ready to receive a character. It goes low while processing the character. DA is an input to the microcontroller. A short strobe on this line tells the microcontroller that data is ready to be received and put out on the display.

Since my friend Greg owns the rights to the code, but I have the right to distribute the IC's, I can sell them at the price he is charging me, $25 ea. Trust me, this leaves me with nothing in my hands. I'd only do this to help people who are stuck needing simple text video with a solution. The D/A conversion is the standard 2 1N4148 diodes thru 3 resistors for 75ohm out. The other 2 IC's are a 74HC166 shift register and a 74HC74 for dividing the 14.31818MHz clock in half to control the timing of the shift register. Obviously you need a 14.31818 crystal 2 18pF caps and a couple resistors, but thats nothing.

I was thinking of putting a small board together with express pcb that just contained the video section. The only thing Greg has left to do is to install the autoscroll routine which is the routine that when the cursor hits the 40th space it scrolls to the next line.

I'll try and post some schematics soon. Keep in mind this was designed as specific purpose and not for most hobbiests. The firmware that controls the video is nothing shy of brilliance in my opinion. I only need to replica the 40 X 24 terminal section of the Apple 1. It was similar to the TV typewriter of the mid 70's by Don Lancaster I believe.

Sorry if I'm rambling on, I've been up for 16 hours and the screen is getting blurry. Let me know if you have any more questions. Oh, FYI Debco has standard 1MHz 6502's (referb I believe) for just over $4 each. I just got 10 and they have date codes of like '83 '82 on them. Not a bad price.