Tag Archives: hardware

Fluxengine disk reader

I’ve build a drawbridge disk reader in the past:
I found an even more interesting project.

I was looking for a solution to my XT laser problem.

And found this! The fluxengine

An open source project using a small controller board.
“Flashing” some software on the board and soldering a pinheader was easy.
When connecting a flat cable and a floppy drive, you end up with a device which can read many formats. Including dos 1.44/720 and amiga.

Nice package it came in

Using the power from a sata/ide harddisk adaptor

Reading and writing a MSDOS disk, no problem.
Imaging an amiga disk .. easy!

You need to compile some software, but it was well documented

Disk troubles or missing old skool hardware?

I bought a XT Laser/3 a while ago.
And i wanted to get my old programs running on it again.

One of the disk i found was a 5.25 inch boot disk which should contain a boot demo i’ve made in the past with Edk.
But it is the secondary drive in this system. Those old machines lack a bios you can change.
And change A: for B: for example.
Some machines had a program which could alter boot settings. (not this one)
So i was playing with jumpers and dipswitches on the motherboard.
( Drive select / Termination / drive before or after the twist in the flatcable. )

Dipswitches on the motherboard

Wellll leave the boot order for now, i needed to get software on the machine using floppy’s.
I could not find empty HD disks (1.44MB which i wanted to use)
So i took a DD disk and a drill ..

I bought an external usb floppy drive.

Now i have everything to get my programs on the msdos machine.


Diskette didn’t work in the drives.
So i bought new old stock diskettes online.

Now i have everything

WRONG again

Formatted 1.44 disk in USBfloppy drive .. OK
Read in 3.5 drive on the MSDOS machine .. NOT OK
Check drive in MSDOS machine .. is 1.44MB .. OK
… check floppy controller in MSDOS machine .. NOT OKAY
(720kb is 300kbits per second and 1.44 HD 500kbits per second)
So i’m limited to 720kb due to the controller ..

Can the USB Floppy drive read/write 720kb disks .. NO!
( A cheap series made with drives only supporting HD disks )

Alternatives? .. Serial maybe, there is Norton Commander on the MSDOS machine so i could use “link”

Do i still have a USB-RS232 sub-d cable ? YES!
Nullmodem cable? NO
Make a null modem cable .. i’ve made those before .. BUT no sub-d connectors.

I’ve been throwing away too much in the past.

Now i have to buy those things again:

VGA – 8bit ISA – have 2 now
Floppy drive – have one for 1.44
8bit soundblaster compatible – TODO
Nullmodem – well i’ve bought connectors for those

Hercules to VGA

While playing with MuseScore….
(Typesetting some scores for Pipes and Flute)

This came in: WOOOT

Trident 8900C (1024 x768 max 512Kb)

This is a Trident VGA card. While having a 16bit ISA connector, it can work in a 8bits ISA slot.

A while ago i bought a Laser XT/3, that’s the one my parents had.
This is where i did a lot of assembly programming on.
It’s a 8086 cpu, 640K and has a Hercules/CGA graphics card.

I found loads of assembly files and i want to see if i can get it running again.
While some code was written for hercules, ( That’s the monochrome image you see in the example above ) and a few for EGA (4 colors).

Most of it was written for VGA. Probably on a later machine like a 80386?

But i know there are vga cards for 8 bit msdos computers, and i found one. ( This one is even autodetect, so no jumpers to figure out)

So i’ve put this card in the machine, turned it on, and it works!
I’ve got only 2 examples living on the harddisk of the machine, both black and white … 🙂
I have to search for interesting code in hundreds of files.

Some friends of mine, picture was taken from an amiga genlock digitizer
The intro pages of a “amiga emulator” WHERE is the rest??? (end is a cga starfield demo)

Hercules Card

There is not much info available about this card:

  • Max resolution (Hercules) : 720×348
  • 15 pin analog monitor port (CN1)
  • BIOS enabled JP1 Pins 1 & 2 closed
  • BIOS disabled JP1 Pins 2 & 3 closed
  • CGA selected SW1 On
  • MDA (Hercules) selected SW1 Off

Floppy drive boot

My friend EDK and I made some demo’s like

And a boot demo, which was able to start from a bootsector, went into a graphic mode and ran a demo with sound. Edk wrote a sector loader for this.
I have some 5.25 inch floppy disks, labelled boot demo. So i wanted to try this today …
I needed to change the boot order, so i went online to search for jumper settings.

I see a led when it tries to boot, but my disks are probably formatted 720Kb instead of 360Kb, which this drive is.

So …. TODO!

Find a 720Kb floppy drive (5.25 inch), and sort through my code!
There is a 8bit soundblaster compatible soundcard that i bidding on online, hopefully i’ll get it

Assembly and modes

I wasn’t sure how to sort the assembly code into Hercules and VGA compatible, but i used this table (There are also extended modes for higher resolutions)

mode 0x00text 40×25 gray
mode 0x01text 40×25 16 colors
mode 0x02text 80×25
mode 0x03text 80×25 16 color
mode 0x04graphics mode (CGA) 320×200
mode 0x05graphics mode (CGA) 320×200
mode 0x06graphics mode (CGA) 640×200 (B/W)
mode 0x07text 80×25 Hercules
mode 0x0Fgraphics mode 640×350? gray
mode 0x10graphics mode 640×350?
mode 0x11graphics vga 2 colors
mode 0x12graphics vga 16 colors
mode 0x13graphics 320×200 256 colors
# Set VGA mode
    mov ax,13h
    int 10h         ;screen 320x200 256 colours

# Exit VGA mode
    mov ax,3
    int 10h         ;screen  80x25 text
    mov ax,4c00h
    int 21h         ;back to DOS

WIP – Designing a 7seg memory address “spy”

UNTESTED, haven’t got all components yet!

Sometimes when i’m writing code i want to know what’s happening. For example when i’m working on the display, there is maybe no output.
With the above example i can write to address $01F0 (example address), and it will display on the 7 Segment displays.

Upperleft PLD is my address decoder, which has been running for a while now.

Secondary PLD adds the rest of the Addressbus lines, and gives me the opportunity to select in a range of 16 addresses, using jumpers/

The two smaller PLD’s latch the databus data when addressed.
AND decodes a nibble to 7-Segment output for 0-9A-F.
(There are apparently no chips available which do A-F)

I’m going to add the PLD code when everything works. Let me know if you like the idea.

Should be only a few Euro’s

Composite video PCB working

UPDATE 20221108

Soldered the components on the print
No more sync issues! (see post https://www.henriaanstoot.nl/2022/10/19/composite-video-with-atmega328p/ )

There are some duplicate characters, the input device below does not have a proper debounce method.

My temporary input device (note hex 21 is a “!” character)

No need to fix the debounce, the dipswitches are temporary. This will be controlled by the VIA 6522 chip.

UPDATE 20221108 (Connected to second VIA)

PORTB = $5000
PORTA = $5001
DDRB = $5002
DDRA = $5003
clock = $e0

E  = %10000000
RW = %01000000
RS = %00000000

  .org $0200

  ldx #$ff

  lda #%11111111 ; Set all pins on port B to output
  sta DDRB
  lda #%10000000 ; Set top pin on port A to output
  sta DDRA
  lda #$00  ; reset bit
  sta PORTA
  sta clock

  ldx #0
  lda message,x
  beq printborder
  jsr print_char
  jmp print

  jmp loop

        .db 0x01,0x04,0x0C,0x0E,0x10,0x0F,0x08
        .db 0x05,0x0a,0x0a
        .db 0x05,0x0b,0x0b
        .asc "Composite Video 6502 - 20221108"
        .db 0x0E,0x11,0x0F,0x0C
        .asciiz " With 2 pixels "

  ldy #$ff
  bne back

  sta PORTB
  jsr waitloop
  jsr waitloop
  lda clock
  eor #%10000000
  sta clock
  sta PORTA
  jsr waitloop
  lda clock
  eor #%10000000
  sta PORTA
  jsr waitloop

Control codes as from : http://searle.x10host.com/MonitorKeyboard/index.html

Video display control codes:
Hex (Decimal) and meaning
01 (01) - Cursor home (Standard ASCII)
02 (02) - Define cursor character (2nd byte is the curs character, or 00 to turn off) <--New for 3.0
03 (03) - Cursor blinking
04 (04) - Cursor solid
05 (05) - Set graphics pixel (next two bytes = x,y) <--New for 3.0
06 (06) - Reset graphics pixel (next two bytes = x,y) <--New for 3.0
08 (08) - Backspace (Standard ASCII)
09 (09) - Tab (Standard ASCII)
0A (11) - Linefeed (Standard ASCII)
0C (12) - Clear screen (Standard ASCII)
0D (13) - Carriage return (Standard ASCII)
0E (14) - Set column 0 to 79 (2nd byte is the column number) or 0 to 39 for a 40 char line
0F (16) - Set row 0 to 24 (2nd byte is the row number)
10 (16) - Delete start of line
11 (17) - Delete to end of line
12 (18) - Delete to start of screen
13 (19) - Delete to end of screen
14 (20) - Scroll up
15 (21) - Scroll down
16 (22) - Scroll left
17 (23) - Scroll right
18 (24) - Set font attribute for the current line (see elsewhere on this page for details) <--New for 3.0
1A (26) - Treat next byte as a character (to allow PC DOS char codes 1 to 31 to be displayed on screen)
1B (27) - ESC - reserved for ANSI sequences
1C (28) - Cursor right
1D (29) - Cursor Left
1E (30) - Cursor up
1F (31) - Cursor down
20 (32) to 7E (126) - Standard ASCII codes
7F (127) - Delete
80 (128) to FF (255) - PC (DOS) extended characters

7 segment displays/keyboard decoders in SDK’s

There are a lot of old develop boards for all kinds for cpu’s.

These where build to learn machine code programming. Mostly made in the 80’s, and based on populair cpu’s at that time.

I own a some of these SDK’s (Software development Kits)

8085 – SDK85 i bought recently 8085 CPU
Microprofessor-1 (MPF-1) Z80 CPU
And my own 680x based computer

Most of these use a keyboard scanner which is also connected to 7 segment displays.

The way they work is practically the same. There is a VIA or PIA. Versitile interface adaptor, or Peripheral interface adaptor. These have two times 8 bits to control devices.
When using 4 bits and convert these to 16 lines by using a 75ls145 for example. If you put a counter on those 4 bits, you sequently activate 1 of 16 lines. These lines you can use to scan a keyboard matrix OR display a character on a 7 segment display. These display’s won’t hold the data (and show the character) when not activated. The trick is to update de display fast enough so you don’t see the flickering on/off.

Activate a line and read a byte with the VIA = Reading keyboard row
Activate a line and write a byte with the VIA = Display on a segment

These VIA/PIA’s where made with specific timings to match the CPU.

Below you see some different implementations of these keyboard/display combo’s

Thaler 6502 kit
Microprofessor MPF-1 kit (ignore red circle)
SDK85 kit
Eltec 6800
My version using darlington arrays (ULN2003)

When looking at the 8085 version you see transistors being a ULN2003 is a chip with those transistors/amplification enclosed.
It doesn´t draw much current from the bus, and diodes protect the way the current flows.

Generic Matrix Keyboard Print

I only have to check my new design for a generic matrix keyboard once again, and then i’m going to order a few of these prints.

  • 32 keys (2 blocks of 16)
  • 1 key is changeable from generic key to reset signal key
  • jumper header connector VCC, GND, DataAvailable, Reset and 5 data lines

I’ve used the opensource tool freeroute to autoroute the coppertraces

  • From Kicad export PCB in Spectra DNS format
  • Open Freeroute and run autoroute
  • export as Spectra Session File
  • In kicad import this session file again

Autotraced …
Current setup

Raspberry and SSD

I had a crash recently on one of my raspberry-pi’s ..
SDcard failure, they are not made for a lot of write actions.
In the past i’ve changed some images to read only and with a r/w overlay.
Also tmp filesystems in memory .. all not ideal.

So i’ve started to make every RPi ssd bootable.

I’ve got several ssd already from other projects.
Sata to USB adaptors are cheap, only a few euro’s.

Steps to take:

  • Download Raspberry Pi Imager tool
  • Choose OS > Misc Utility Images > Bootloader > USB Boot
  • Select storage and write to a temporary sd-card (Not needed any more after flashing for normal operations)
  • Boot USB with this Micro-SDcard .. i didn’t have a screen connected .. So i just waited a few minutes
  • While i was waiting i wrote a OS image to the SSD using the same imager tool
  • Choose OS > select sata/ssd drive
  • Change options (cog), enable ssh, choose hostname and set password
  • Write to drive
  • Remove sdcard from RPi attach ssd/sata and boot

My 3D printed sdcard case, luckily there was still one in there (32GB kindda big, but it was only for temporary use .. 16GB was broken ..

So .. without attaching a screen or keyboard, just a network cable. I have a running OS on a RPi from SSD

SDK-85 in 2022

I was posting about the 8085 software development kit in may, but now i’ve got one!

I found one online, it is a very clean almost like its never been used version!

More follows!

More info at http://www.bitsavers.org/components/intel/8085/