Maybe I will bring my osi 400 stuff to the upcoming vcfed workshop, If I can go and have coverage at the museum then B On Mon, May 22, 2023, 12:43 PM Bill Dromgoole via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
You just need an ascii keyboard with TTL level outputs for the 440 video board. The input is enabled for one micro second every five milliseconds by the OSI 65V ROM. This means you need a keyboard strobe pulse about 10 milliseconds long for it to work. You can use M. Willigals PC keyboard to apple 1 adapter board for testing purposes if you want. The early version only had a pulse width of 125 microseconds though. I had to use a 74ls123 with a 15K resistor and a 1.1 microfarad capacitor between the adapter and the 440 to get the correct pulse width.
He no longer sells the board but can build your own. http://www.willegal.net/appleii/appleii-kb-int.htm
Bill From: Alexander Pierson via vcf-midatlantic Sent: Monday, May 22, 2023 9:37 AM To: vcf-midatlantic@lists.vcfed.org Cc: Alexander Pierson Subject: [vcf-midatlantic] Ohio Scientific 440 Video Board