Search found 1905 matches

by mrtinb
Mon Dec 25, 2023 10:28 pm
Forum: Hardware
Topic: Nominal video output signal on ULA pin 16 ZX81 rev 1?
Replies: 15
Views: 1455

Re: Nominal video output signal on ULA pin 16 ZX81 rev 1?

From what I've seen online the sync signal should not be 0v. It’s because the ZX81 does not follow the composite standard. It sends a signal where the difference from bottom of signal to top of signal is ok. Old TVs think this is ok. It does this to avoid making a more complex circuit that sends ne...
by mrtinb
Sun Dec 24, 2023 4:50 pm
Forum: Hardware
Topic: Zeddy white screen after memory upgrade
Replies: 17
Views: 1699

Re: Zeddy white screen after memory upgrade

This issue around the holidays, is what we call: White Christmas. :lol:
by mrtinb
Sun Dec 24, 2023 10:58 am
Forum: Hardware
Topic: First zeddy boots but....
Replies: 19
Views: 2398

Re: First zeddy boots but....

Why not go full 64k with battery backed up RAM? It’s even possible to replace ROM area with RAM, so you can load your own custom ROMs.

https://web.archive.org/web/20210224003 ... mories.htm
by mrtinb
Sun Dec 24, 2023 10:35 am
Forum: Hardware
Topic: First zeddy boots but....
Replies: 19
Views: 2398

Re: First zeddy boots but....

If you don’t want to soldier you can get this modern external RAM board:

https://www.ebay.co.uk/itm/116017640518
by mrtinb
Sat Dec 23, 2023 11:11 pm
Forum: Hardware
Topic: First zeddy boots but....
Replies: 19
Views: 2398

Re: First zeddy boots but....

I have several storage options. But if you have an Arduino, you just upload the firmware for TZXduino, and connect the output pin for Ear to the ZX81. That pulses 5V to the ZX81 from an SD card. That works flawlessly. So find anything that can send outputs that pulses from 0V and 5V. It needs to be ...
by mrtinb
Thu Dec 21, 2023 2:11 pm
Forum: Hardware
Topic: Memory Card storage options
Replies: 11
Views: 1675

Re: Memory Card storage options

msknight wrote: Thu Dec 21, 2023 1:30 pm The ZX-Wespi requires Windows to do some of the work, and I'm a Linux user, so couple that with my minimal electronics experience that's down the list of options.
I've programmed my ZX-Wespi on a Mac.
by mrtinb
Thu Dec 21, 2023 12:36 pm
Forum: Hardware
Topic: Memory Card storage options
Replies: 11
Views: 1675

Re: Memory Card storage options

As a ZXpand might be difficult to get hold of, and import to the UK might be a problem, I would suggest adding a ZX-Wespi to your Zeddy. You'll only need a cheap ESP32 microcontroller and a few resistors and a capacitor. This device stores your programs into the microcontrollers Flash, and you can u...
by mrtinb
Wed Dec 20, 2023 8:32 am
Forum: Hardware
Topic: ZX81 floppy disk systems
Replies: 17
Views: 6444

Re: ZX81 floppy disk systems

8008guy wrote: Wed Dec 20, 2023 4:02 am In any case I am still looking for the rom code for the fd-zx. They seem to be rare,I hope someone archived the rom.
Maybe
XavSnap wrote: Mon Dec 11, 2023 9:36 pm XavSnap
has come across this firmware.
by mrtinb
Tue Dec 19, 2023 8:05 pm
Forum: Sinclair Misc
Topic: MERRY KMAS
Replies: 1
Views: 1406

Re: MERRY KMAS

Thank you for your e-postcard. Marry K-mas to you too.
by mrtinb
Sat Dec 16, 2023 3:54 pm
Forum: Software
Topic: Word Processor/Text Editor?
Replies: 10
Views: 16292

Re: Word Processor/Text Editor?

Yes. It sounded much alike.