Add S/PDIF optical output to board

polpo / picogus

Emulation of ISA sound cards on Raspberry Pi Pico (GUS, SB/Adlib, MPU-401, Tandy, CMS) with USB mouse/joystick support

GNU General Public License v2.0

551 stars 40 forks source link

Add S/PDIF optical output to board #41

Open nikitalita opened 5 months ago

nikitalita commented 5 months ago

Adds optical output to the board. Only increases the manufacture price by 2 dollars due to the remapping of the LED pin to S/PDIF output.

No firmware changes yet to enable this; this is just to confirm my design before I send this off to be assembled.

Major changes:

The LED still exists, but its pin is now used for S/PDIF output. This means it will blink along with the S/PDIF output. This will necessitate some changes to the firmware to make it not just spew all 1s when loading.
I had to move the power regulator from the front of the board; it's still fairly close to VSYS
The volume control lines for the wavetable had to be moved to accommodate a better path for the SPDIF line; these run at 250khz so it shouldn't be a problem.
Various fixes (fixing model paths, adding the bracket to the render, removing non-existent libraries, ensuring symbols exist in project library)

skadarnold commented 5 months ago

I love this idea and have been hoping for a good spdif solution for a while now. I wonder if it also might work to do a optical / 3.5mm combo similar to this design for the MiSTer IO board. https://github.com/MiSTer-devel/Hardware_MiSTer/blob/master/releases/iobrd_6.1.pdf The LED sits behind the 3.5mm port with an open back and uses a 3.5mm toslink cable or adapter instead.

Also, it could be nice to have just a simple pinout that connects to one of these external TTL boards to have as optional. https://www.amazon.com/gp/product/B07FJMD7BF/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

nikitalita commented 5 months ago

I love this idea and have been hoping for a good spdif solution for a while now. I wonder if it also might work to do a optical / 3.5mm combo similar to this design for the MiSTer IO board. https://github.com/MiSTer-devel/Hardware_MiSTer/blob/master/releases/iobrd_6.1.pdf The LED sits behind the 3.5mm port with an open back and uses a 3.5mm toslink cable or adapter instead.

Yeah, that might work, but it's really only something you do if you have limited board space, as in the case of the IO board; the mini-toslink cables are harder to find than the regular ones, and you can't do both digital and analog output at the same time with this.

Also, it could be nice to have just a simple pinout that connects to one of these external TTL boards to have as optional. https://www.amazon.com/gp/product/B07FJMD7BF/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

yeah, i might do that after this one is validated, i sent it off to be ordered