My BBC Acorn model B is working again. The original monitor is still dead.
Time to play with some machine code and ROMs.
My machine has a NFS rom installed. (NetFS)
Econet was Acorn Computers’s low-cost local area network system, intended for use by schools and small businesses. It was widely used in those areas, and was supported by a large number of different computer and server systems produced both by Acorn and by other companies.
I found a ROM online called Gremlin. It is a 16K rom file. But at the moment I only got some 28C64 (8k) or 28C256 (32k) eeproms.
32k it is. But de beeb having address line A14 floating high, I need to flash the upper 16k of the 32k ROM.
Ben posted a youtube about Wozmon running on his 6502.
In 1976, Steve Wozniac wrote what’s commonly known simply as Wozmon.
Wozmon is a machine-code monitor program written by Wozniak for the Apple 1. In Only 256 bytes ! Being pure 6502 code easily adaptable. A monitor program allows you to view/edit and run machine code using simple commands.
I’ve got a different setup as Ben’s computer. But changing the necessary, and it will run on my 6502.
I’m not using rs232 voltage levels (-7 till -25 and +7 till +25 volts). I’m using a usb serial uart standard 5v leveling stick …
For address decoder see other post
Simplified schematic of my UART/ACIA
Compiling the Wosmon gave me an error, DEC is not a valid opcode for a bare 6502 .. but we have a 65c02. Solution: Add -c02 extra opcodes
error 1 in line 187 of "wozmon.s": illegal operand types
> DEC ; Decrement A.
# fix .. add -c02
vasm6502_oldstyle -c02 -Fbin -dotdir wozmon.s
Below Apple I Manual with the sourcecode for Wozmon
Uploading didn’t work Solution: Using chrome it had access to the usb port to upload, firefox didn’t work
The program didn’t compile, faulty or zero size hex file. Solution: Wrong Maqueen library was in the examples (After changing, needed version update also, see below)
Not everything is in Dutch (I like English, but this is for the boy), maqueen V2 needed a lot of translation. (So we joined https://crowdin.com/project/makecode/nl to help translating the libraries)
Apparently my AI camera can be connected to this robot!
Our bedroom has a shelly dimmer, this one is connected with a wall switch and is being controlled by Domoticz, Home Assistant and NodeRed.
I had to fix some stuff, so this was a perfect time to jot down some notes.
I’ve wired it up like this: (I’ve got a Line wire in my ceiling socket, so i placed the module there instead of the wall socket)
Configure the Shelly as mentioned in the manual. After that do the following: Advance > Developer settings : (Enable CoIot if you want a easy auto detect for Home Assistant) Enable MQTT (This will DISABLE cloud ! ) Server: the ip number of your Mqtt Broker
Next I did was:
Now the wall switch will change/toggle what the current state is. (If the light is off, and you switch it on using Mqtt, you probably needed to hit the switch two times to turn it off again. Not so with this setting.)
My Nodered Flow ( Not using the Shelly palette nodes in this example)
The Mqtt IN node sets the state of the switch when you use the wall switch! Cozy turns light on at a specific level. The slider send an off command when 0% selected, else an on command and the sliders value.
I wrote a little python script which checks the checksum of a Bios.
In a previous post i used hexedit to play around changing a Bios dump.
Below posted python script calculates the checkum using the following:
Add all bytes in the file and do a modulo 256 on this number. The output should be 0.
My previous edit gave me a output of C2, so I changed an unused byte FF into (FF-C2) 3D. No more checksum errors when booting!
Next to do, get a Bios like Glabios or PcXtBios to start my own code from a secondary Eeprom.
import sys
# Bios sum modulo should be 0
# edit last or unused byte to fix
# python bios-checksum-test.py MYROM.edit.checksum
# 0
f = open(sys.argv[1],'rb')
m = f.read()
print '%x' % ( ( sum(ord(c) for c in m) & 0xFFFFFFFF ) % 256 )
Python3
import sys
# Bios sum modulo should be 0
# edit last or unused byte to fix
# python bios-checksum-test.py MYROM.edit.checksum
# 0
f = open(sys.argv[1],'rb')
m = f.read()
checksum = ( ( sum((c) for c in m) & 0xFFFFFFFF ) % 256 )
print(checksum, 'in hex =', hex(checksum))
