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Roman Krupnin 90e6151613 init repo		2025-01-28 19:17:01 +03:00
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README.md	init repo	2025-01-28 19:17:01 +03:00

README.md

sound card with sn76489

I accidentally stumbled across the sound chip sn76489. Since it can only be controlled via outputs, it is well suited for the extension-retro of lb3361. This is my attempt for a Gigatron sound card (Rev.3 still in work).

Unfortunately, I haven't had any success so far in producing a reasonable sound on the board. Now I have finally discovered the cause of the problem. The SN76489 is available in two different pinouts. The difference is mirrored data pins.

SN76489 Pin	Pinout 1	Pinout 2
3	D0	D7
2	D1	D6
1	D2	D5
15	D3	D4
13	D4	D3
12	D5	D2
11	D6	D1
10	D7	D0

Pinout 1: https://map.grauw.nl/resources/sound/texas_instruments_sn76489an.pdf

Pinout 2: https://en.m.wikipedia.org/wiki/Texas_Instruments_SN76489

I solved the problem on the breadboard for now.

I'm still testing a small adapter board. When she leaves I will post it here. I will also rework the PCB itself.

First tests (fast cell phone video): https://www.youtube.com/watch?v=wv5x-WD0vzI