The Tandy 1000 ISA sound card brainstorm thread.

Discussion about old PC hardware.

Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby matze79 » 2017-8-10 @ 06:53

Hm the SSL certificate of lotech site is outdated,
i think there is something going on... maybe we will lose lotech in future.

Scali, do you own a Card and can make high resolution fotos of front and backside ?
its time to get back to bring the idea to a final working card, with proper amplifier and muting.
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby keropi » 2017-8-10 @ 07:18

Lo-Tech stopped selling PCBs - no idea what is going on or if the service will return
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby matze79 » 2017-8-10 @ 08:06

maybe seems something is keeping james from his hobby.
Sad, as i really would like to buy 2-3 EMS Board PCBs and some other Projects.
Some Schematics also not avaible.
The EMS Board can be redrawn, Schematic is avaible.
i grabbed a whole offline version of the lotech site before it will eventually went down.
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby matze79 » 2017-8-10 @ 09:00

had few minutes time to draw backside..
maybe i have later time to reconstruct front and make some schematic files.
Attachments
first_steps.jpg
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby matze79 » 2017-8-13 @ 04:50

pretty much done.. drawing now a eagle schematic.

clonetech.png


with limited time this is pretty annoying..

i don't want wait longer.
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby keenerb » 2017-8-15 @ 12:56

I got in touch with James. He's fixed the SSL issue on his webserver.

Hopefully he has time to hop back on this project soon.
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby matze79 » 2017-9-11 @ 14:02

Yes, seems to work again.

I'm back from France, so now i will have some time to make some tests with the tandy soundboard stuff..
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby matze79 » 2018-1-29 @ 16:01

I'm still working on this :)

Scali mentioned a Counter can be used for muting, but i need to cut the SN76489 from ISA Bus to send the commands right ?
if not i will send the data to the whole bus ?

Is there a way to lock bus for a few ms do send the commands ?
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby Scali » 2018-1-29 @ 16:16

matze79 wrote:Scali mentioned a Counter can be used for muting, but i need to cut the SN76489 from ISA Bus to send the commands right ?
if not i will send the data to the whole bus ?


Yup, you won't want to have the commands 'leak' onto the ISA bus.

matze79 wrote:Is there a way to lock bus for a few ms do send the commands ?


I don't know the details of all ISA communication, but as far as I understand it, a DMA transfer is the only way an ISA card can initiate anything. Any other operation can only be done in response to the CPU/motherboard initiating any kind of read/write operation, where you can insert wait states.
So perhaps you can 'fake' a DMA transfer, this is how cards tended to implement bus mastering back in the day. See at the bottom of this page:
http://pinouts.ru/Slots/ISA_pinout.shtml

My idea was that it may be simpler to solve it on the card itself, so you multiplex the data and control lines.
Eg, if you have some and-ports, you can have a single bit select either the ISA pins as input, or the counter circuit. This way the chip is either connected to the ISA pins, or to the counter circuit, but never both at the same time. Also the counter is never connected to the ISA pins.
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby Great Hierophant » 2018-1-31 @ 17:17

Why not use a '244 whose enable is controlled by the counter? The 244 is connected to the data lines and when the counter is active, the '244's outputs are disabled. This should prevent data writes from getting to the bus. Once the counter finishes its job, it flips the enables on and allows for communication.

Actually given that the SN76489 is a write only device, diodes on the data lines to prevent writes from reaching the bus should work just as well.
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby matze79 » 2018-2-03 @ 14:21

CE/OE and Ready also needed to cut off from the Bus, i'm currently thinking about howto do this.

Maybe i will try this:
A MCU will allow to pass them trough, which will keep the Part count down.
No need for additional transistors. Just use some more I/O Pins.

Do the Stuff in Software instead.
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby gdjacobs » 2018-2-03 @ 16:10

Diodes or TTL buffers?
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby matze79 » 2018-2-06 @ 15:18

Software route is not as good as i thinked.
It does work with two 244 ICs routing signals trough and using the MCU to mute.

Routing CE etc to the MCU and control them with MCU, and pass trough after silencing the SN76489 adds additonal delays.
works but not very well.

I had another idea, using a power on timer, so you can set a timelimit with a variable resistor.
So you can give your Computer time to boot up and exec sndoff commands.
Using a NE555.

This is really easy, simply mute Amp Output.
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby Great Hierophant » 2018-2-06 @ 17:42

matze79 wrote:Software route is not as good as i thinked.
It does work with two 244 ICs routing signals trough and using the MCU to mute.

Routing CE etc to the MCU and control them with MCU, and pass trough after silencing the SN76489 adds additonal delays.
works but not very well.

I had another idea, using a power on timer, so you can set a timelimit with a variable resistor.
So you can give your Computer time to boot up and exec sndoff commands.
Using a NE555.

This is really easy, simply mute Amp Output.


The 555 timer idea is a rather ingenuous solution, but it should be able to be triggered by both a powering on as well as a reset. I would like it if there was an external timer control pot as well as a volume control port accessible from the rear panel.
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Re: The Tandy 1000 ISA sound card brainstorm thread.

Postby matze79 » 2018-2-11 @ 10:32

I'm now testing another version..

Using a FlipFlop and trigger it on chip access.
So Sound will enable on port access.
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