Recent content by gottahack

If anyone wants it, I wrote code for the microcontroller on the display board, but I wrote it for an ATmega8515-16PU which is pin-compatible with the original 8751. It requires a board mod because the Reset pin on the AVR has the level sense reversed, but Pt68k5 says it is working with his trainer.

Sorry, no, it was something I threw together just to see if it worked, but the technique was pretty simple. I can't remember what display I used, I was working for Datapoint at the time. Might have been a Hercules monochrome card but it might have been too early for that.

Yes, I can see the 4x4 grid, I think that's why I'm seeing posterization in the images. You might try error diffusion with just single black/white pixels, i.e. full 4k resolution. I wrote a program that did that back around 1980 (though with a different type display) and I recall it looking...

I think you could produce better images by using error diffusion.

It isn't real code since I thought you were working in assembler. It's just documentation (that sort of looks like C) of what the signals are doing. You load the group latches while the column drive is turned off, then turn on the drive for the LEDs for that one column for about 264...

From what I'm seeing, the multiplexing looks something like this: while (1) for (column = 0; column < 4; column++) for (group = 0; group < 10; group++) P0 = data[group][column] P2 = 0xf0 + group /* strobe group latch */ P2 = 0xff P2 =...

P2 bits 0 thru 3 selects one of the display groups (0 thru 9), bits 4 thru 6 select one of the columns (0-3). You can see the groups and columns in figure 3-8 on page 7 of the csa80.pdf file. I'll see if I can get the multiplexing sequence and timing numbers from my display board for you. On...

New update. Added more analog stuff on the 8751 board. The RESET button biasing looks wonky, but I've checked the schematic against the board several times and it's right. I'll just have to try the board under power and see what the voltages are.

I'm studying up on the 8051 architecture and instruction set, I've never programmed one before. I wrote some code for an 8748 once, but that was about 40 years ago.

I updated the schematic with some more details from my suitcase machine, especially the P3 connector pins. (Not sure if the Trainer's display board is identical.) Kicad substituted the MCU symbol with a new one, so if you have any problems reading it you might try upgrading Kicad. Edit: Aw...

Thanks, I have Kicad, so I can see the display file OK. Which are the 4 display segments that are working?

If you have display code that is partially working, can you post the source? I have a couple of AT89S52 chips here that I can debug with. What hardware documentation did you use as reference to write the display code? Do you have a schematic drawing?

It's pretty simple. One character per key press. 0 thru F is '0' thru 'F' in ASCII. HEX is 'H', RESET is 'R', BREAK is 'I' and ENTER is CR (x0d). Edit: Oh, looks like Bruce Tomlin beat me to it.

No, haven't worked on it yet, other things had priority. The lower board is just the Motorola MEX68KECB board, I think they're all the same. Any luck on the display multiplexing? If you don't have it yet, I decoded the keyboard-generated serial characters.

No luck yet, I just get the HALT light no matter the ROM configuration. Something broke.