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Re: Sunday with my SuperBoard II

Posted: Mon Sep 26, 2016 7:29 pm
by stm
BillO wrote:The device operating the DD line must be open collector or open drain. The DD, when used with the 32K RAM board is pulled high by a resistor on the 600 board so you cannot use a device with an active pull-up.
So if I want to drive the 5V DD line with a Raspberry Pi 3.3V GPIO output, I would have to implement the open collector circuit with an extra transistor and pull-up resistor, is that correct?

Re: Sunday with my SuperBoard II

Posted: Tue Sep 27, 2016 12:48 pm
by BillO
There is a pull-up already on the 600 board, you should not need another. But yes, it would be easiest to take the GPIO of the RPi trough a 2n3904 transistor or small mosfet, like a 2n7000. If you wanted to get deeper into the RPi, there may be a way to turn off the active pull-up on it's GPIO lines. They may then also be 5V tolerant. I'm not sure about that but this capability exists in most microcontrollers like AVRs and PICs.

Re: Sunday with my SuperBoard II

Posted: Fri Feb 22, 2019 6:04 pm
by waltermixxx
happy to report, i have just upgraded my OSI Superboard II (In a fancy home made case) to 40191 bytes of ram :)
I used one of BillO's 32K ram boards generously provided to me by Steve Gray. I remebered to solder the link for +5 volts
and upon pressing the Break Key, then C, then Enter on memory, It ran it's initial test, and reported I had 40191 Bytes of free ram. :)
Excellent!!

Thanks to BillO and to Steve. :)
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Cheers.

Re: Sunday with my SuperBoard II

Posted: Fri Feb 22, 2019 7:19 pm
by Steve Gray
Awesome! Good thing I ordered two back in 2015! ;-)

Steve

Re: Sunday with my SuperBoard II

Posted: Sat Feb 23, 2019 7:31 pm
by waltermixxx
Yup Very grateful you did, and thanks again for giving me one. :)
I am having a blast with the extra ram :)

Cheers. :)

I had to trim the legs down pretty short to have it fit on the board and not inter fear with the case.

thanks again :)

Re: Sunday with my SuperBoard II

Posted: Sun Feb 24, 2019 12:56 pm
by BillO
Cool!

Re: Sunday with my SuperBoard II

Posted: Sun Feb 24, 2019 3:11 pm
by Steve Gray
BillO wrote:
Sun Feb 24, 2019 12:56 pm
Cool!
Hi BillO,

Thanks for designing the board. Do you have any more plans for this board? Will you make more? I was hoping to try your board with my 505 board. That would eliminate the need for the OSI 527 board. How hard would it be to make a 64K skinny dip version to get 48K ram?

Steve

Re: Sunday with my SuperBoard II

Posted: Wed Mar 27, 2019 5:39 pm
by BillO
Hi Steve,

Sorry for the late reply.

I'm not planning any modifications to these boards and I'm out of the small ones with only 2 of the RAM/ROM boards left. I may order more as I'm sending another board out for manufacture soon.

I was thinking of designing a back-plane to go on the 600 board. Maybe 4 slots on it. I could look at putting another 8K chip on there as an option - if it still leaves enough room for sufficient I/O :mrgreen: .

Re: Sunday with my SuperBoard II

Posted: Wed Mar 27, 2019 11:41 pm
by Steve Gray
BillO wrote:
Wed Mar 27, 2019 5:39 pm
Hi Steve,

Sorry for the late reply.

I'm not planning any modifications to these boards and I'm out of the small ones with only 2 of the RAM/ROM boards left. I may order more as I'm sending another board out for manufacture soon.

I was thinking of designing a back-plane to go on the 600 board. Maybe 4 slots on it. I could look at putting another 8K chip on there as an option - if it still leaves enough room for sufficient I/O :mrgreen: .
I ordered some of the same pal chips and i was hoping to learn how to program them. I’ve been wanting to learn programmable logic for years... I have some 64k skinny dip ram so maybe I’ll try making my own ram expansion with your code as a start.

Steve