Tag Archives: electronics

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

reset:
  ldx #$ff
  txs

  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
print:
  lda message,x
  beq printborder
  jsr print_char
  inx
  jmp print

loop:
  jmp loop

message:
        .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 "

waitloop:
  pha
  tya
  pha
  ldy #$ff
back:
  dey
  bne back
  pla
  tay
  pla
  rts

print_char:
  sta PORTB
  jsr waitloop
  jsr waitloop
  lda clock
  eor #%10000000
  sta clock
  sta PORTA
  jsr waitloop
  lda clock
  eor #%10000000
  sta PORTA
  jsr waitloop
  rts

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

Prints from China

A few weeks ago i designed a print using Kicad.

Today they have arrived!

Now I have to wait a little more .. A 74HTC166 and a straightup RCA connector.

I the past, a long time ago i made my own single side pcb’s using acids.
A messy job, often gone wrong.

Old skool example https://www.youtube.com/watch?v=_PwCp3A3RSk

Or https://www.circuitsonline.net/artikelen/view/1/print

Composite video with Atmega328p

I started to get some composite video generated with a arduino for my 6502 project.

UPDATE: 20221021

It is based on Grant Searle’s design, and yesterday I had some signals on my scope which looked like a screen with a character. But my monitor would not recognize a usable signal.

Today I tried a second version and another set of chips and crystals.

It looks like a signal, but I can’t see a clock pulse from the crystal?! So .. how?

Maybe I used a bad power supply. And killed something?

UPDATE: 20221021

After switching to another power supply, and checking the atmega328p fuses again (also wrong) .. at least SOME success!

Still a little sync problem, but i’ve got a blinking cursor!
Some minipro info
#Erase
minipro -p ATMEGA328P@DIP28 -E

#Flash hex code
minipro -p ATMEGA328P@DIP28 -w SBCVideo.hex

#Flash fuses
minipro -p ATMEGA328P@DIP28 -e -c config -w fuses

#Used fuses file
fuses_lo = 0xf7
fuses_hi = 0xd9
fuses_ext = 0xff
lock_byte = 0xff

#Dump all from atmega328p
minipro -p ATMEGA328P@DIP28 -r dump -f ihex


Some info about the fuses:
https://www.allaboutcircuits.com/projects/atmega328p-fuse-bits-and-an-external-crystal-oscillator

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.
6522/6820/8255

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 …
Front
Back
Current setup

6502 update

  • New amplifier part using a LM386
  • Buzzer and led on VIA 2, blinky and sound timed by the internal timers of the 6522
  • ACIA testing still going on, writing software
  • Mini matrix keyboard removed, and used the temporary cursor buttons for the test with a rom which allows for a 8bits upload method using a arduino and the 6522. (I’m working on the big keyboard)

Work in progress code

PORT2B = $5000 		; VIA PORTB
PORT2A = $5001 		; VIA PORTA
DDR2B = $5002  		; Data direction register
DDR2A = $5003  		; Data direction register

PORTB = $6000 		; display
PORTA = $6001 		; control display + matrix keyboard
DDRB = $6002  		; data direction register
DDRA = $6003  		; data direction register
SID = $7000   		; sid base address

E  = %10000000		; enable bit
RW = %01000000		; RW bit 
RS = %00100000		; Register Select bit 
HOME = %00000010 	; VIA PORTB HOME command
DADDR = %00010000 	; VIA DADDRESS

LINENO = $0200		; temp address linenumber (move to other location)
NEXTLINE = 40		; 2x16 Chars but internally 40


  .org $8000

reset:
  ldx #$ff
  txs		; reset stack

; ###################################################
; #                 DISPLAY CONTROL                 #
; ###################################################
; VIA Setup

  lda #%11111111 	; Set all pins on port B to output
  sta DDRB
  lda #%11100000 	; Set top 3 pins on port A to output
  sta DDRA

; DISPLAY Setup
  lda #%00111000 	; Set 8-bit mode; 2-line display; 5x8 font
  jsr lcd_instruction
  lda #%00001110 	; Display on; cursor on; blink off
  jsr lcd_instruction
  lda #%00000110 	; Increment and shift cursor; don't shift display
  jsr lcd_instruction
  lda #$00000001 	; Clear display
  jsr lcd_instruction

; ###################################################
; #             PRINT MESSAGE LINE NO 0             #
; ###################################################
  lda #0  		; set line number
  sta LINENO      	; store for subroutine
  jsr gotoline		; move cursor

  ldx #0		; message index pointer
print:
  lda message0,x 	; start of message
  beq nextprint      	; stop when null in message (asciiz <- Zero padded)
  jsr print_char	; print char
  inx			; incr index
  jmp print		; resume print
; ###################################################
; #             PRINT MESSAGE LINE NO 1             #
; ###################################################
nextprint:
  lda #1  		; set line number
  sta LINENO      	; store
  jsr gotoline
  ldx #0  		; index pointer                 
print2:
  lda message1,x  	; absolute address message + x in A
  beq sidsound        	; if x is 0, end of message     
  jsr print_char  	; jump subroutine
  inx             	; increment x
  jmp print2      	; loop print2



; ###################################################
; #             SID SOUND                           #
; ###################################################
sidsound:
  lda #0		
  sta SID+$5		; attack/decay duration
  	
  lda #250
  sta SID+$6		; sustain level/release duration
  	
  lda #$95		; frequency voice 1 low byte
  sta SID+$0
  	
  lda #$44		; frequency voice 1 high byte
  sta SID+$1
  
  lda #%00100001	; sawtooth + gate
  sta SID+$4		; control register voice 1
  
  lda #$0f		; filter mode and volume (bits 3-0 main volume)
  sta SID+$18		; filter mode and volume



; ###################################################
; #             2ND VIA                             #
; ###################################################
  lda #%11111111 	; set port A output
  sta DDR2A

  lda #%11111111	; all ones!
  sta PORT2A
; ###################################################
  lda #%11111111 	; set port A output
  sta DDR2A

  lda #%11111111	; all ones!
  sta PORT2A



; ###################################################
; #             MAIN PROGRAM LOOP                   #
; ###################################################
loop:
  jmp loop
;                   1234567812345678
message0: .asciiz  "VIA 1,2 SID TEST"
message1: .asciiz  "   FASH  2022   "

; ###################################################
; #             ONLY SUBROUTINES                    #
; ###################################################

; ###################################################
; #             Subroutine gotoline                 #
; # Moves character placement position on display   #
; # Needs : $LINENO ADDRESS                         #
; # Exit values : -                                 #
; # Destroys registers: -                           #
; ###################################################

gotoline:
  pha                             ; store a
  txa
  pha                             ; store x
  ldx LINENO
  lda #HOME                       ; cursor down
  jsr lcd_instruction
  lda #$80
nextline:
  ldx LINENO
  cpx #00
  beq endnextlines
loopline:
  adc #40
  jsr lcd_instruction
  dex
  stx LINENO
  jmp nextline
endnextlines:
  pla                             ; pop a
  tax                             ; a to x
  pla                             ; pop a
  rts




; ###################################################
; #             LCD SUBROUTINES                     #
; ###################################################
lcd_wait:
  pha
  lda #%00000000  ; Port B is input
  sta DDRB
lcdbusy:
  lda #RW
  sta PORTA
  lda #(RW | E)
  sta PORTA
  lda PORTB
  and #%10000000
  bne lcdbusy
  lda #RW
  sta PORTA
  lda #%11111111  ; Port B is output
  sta DDRB
  pla
  rts
lcd_instruction:
  jsr lcd_wait
  sta PORTB
  lda #0         ; Clear RS/RW/E bits
  sta PORTA
  lda #E         ; Set E bit to send instruction
  sta PORTA
  lda #0         ; Clear RS/RW/E bits
  sta PORTA
  rts
print_char:
  jsr lcd_wait
  sta PORTB
  lda #RS         ; Set RS; Clear RW/E bits
  sta PORTA
  lda #(RS | E)   ; Set E bit to send instruction
  sta PORTA
  lda #RS         ; Clear E bits
  sta PORTA
  rts

nmi:
  rti

irq:
  rti

  .org $fffa
  .word nmi
  .word reset
  .word irq
;  .word $0000

So i wasn’t being stupid designing a dual matrix keyboard thingy

As previously posted, i had an idea to create a dual matrix keyboard mashup using available components.

I mentioned that “it should theoretically work”. But only being using atf22v10c for a couple of days. It was a long shot.

I’ve put it to the test .. and it worked first time.

I can use above, to connect my extended matrix keyboard to a 6522 VIA chip using 5 pins and sending a data available signal to CA1.

This keyboard i was planning to use

Generic matrix keyboard

In this case designed for my 6502, but it is a generic setup.

I it just a dual 16key matrix decoder merged together. You can probably use this with raspberries, arduinos etc.

I wanted to use 74C923 but these are nowhere to be found. And even then, the number of keys wil be 20.
So i am tying together two 74C922 using some logic in a PLD.

First draft

It wil be something like above. Using the data availabe signal i can combine both 16key matrixes. (In theory .. it is all untested)

PLD Code

GAL22V10
Address Decoder

PHI2 DA0 DA1 D01 D02 D03 D04 D11 D12 D13 D14 GND
NC D0 D1 D2 D3 D4 DA NC NC NC NC VCC

DA = DA0 + DA1
D0 = D01 & DA0 + D11 & DA1
D1 = D02 & DA0 + D12 & DA1
D2 = D03 & DA0 + D13 & DA1
D3 = D04 & DA0 + D14 & DA1
D4 = DA1 

DESCRIPTION
Key matrix merger

I’ve got my new keys of the keyboard in today!

  • 0-F – hex keys
  • G = Go
  • R = Reset
  • S = Step
  • M = Memory
  • Cursor keys (up/down for memory locations)
  • ??? I’ve got room for 8 more keys

My inkscape template (keys are 10/10mm)

Printed on white and red paper

https://media.henriaanstoot.nl/keyboardmatrix.svg

6502 Update

New address decoder in place!
Connected RAM/ROM/SID/VIA1/VIA2 and ACIA

ROM8000-FFFF
SID7000-700F (sound)
VIA16000-60xx (Hex key matrix)
ACIA6800-68xx (serial)
VIA25000-50xx (led test at the moment)
RAM0000-3FFF

To plan: Bigger maxtrix keyboard and other displays

ACIA 6551

Got a serial connection working between the 6502 and my linux machine!

At the moment when a reset occurs , hello is being printed.
Text typed in the minicom terminal, is echo-ed back and displayed on the LCD display.

Things learned: Do not trust internet schematics blindly!

The crystal used for the ACIA (pin 6/7 1.8432Mhz needs a 1M ohm resistor parallel over the crystal, and a 30nF capacitor from pin 7 to GND

When using a terminal emulator, and using 3 wires. Disable hardware handshake.

Keyboard rewired.

What didn´t work as planned:

New amplifier schematic for the SID. There is too much noise.

Amplifier with a LM628

Bought a dual power supply (5V and 12V). But this one has a lot of signal noise on the SID part and even my battlestation speakers!

LED test 2nd via

PORTB = $5000 ; VIA PORTB
PORTA = $5001 ; VIA PORTA
DDRB = $5002  ; Data direction register
DDRA = $5003  ; Data direction register

LED  = %10000000

	.org $8000

reset:

	lda #%11100000 ; Set top 3 pins on port A to output
	sta DDRA

	lda LED 
	sta PORTA

loop:		; done loop until doomsday
	jmp loop

irq:
nmi:
	.org $fffa
	.word nmi
	.word reset
	.word irq

ACIA part

ACIA_RX = $6800
ACIA_TX = $6800
ACIA_STATUS = $6801
ACIA_COMMAND = $6802
ACIA_CONTROL = $6803

    lda #$00
    sta ACIA_STATUS
    lda #$0b
    sta ACIA_COMMAND
    lda #$1f
    sta ACIA_CONTROL