Atari ST OPL3 cart schematics

[DoG]

Yes. 1,6mm on 4 or even more layers as well

[nokturnal]

I think I have something to send to pcb manufacturer.
I've printed pcb and checked it with F030 ROM port, so it should be fine. Debug pins could be moved 1cm to the left, but I will probably get around this by using horizontal connector with longer pins.

[nokturnal]

So, pcb prototype arrived, but there are some issues with it. I've didn't check properly footprints of DAC/opl3 (I assumed they are allright like before) and pcb uses something else than I've designed sometime ago (not sure how it happened, probably during pcb redesign frenzy I've replaced footprints with KiCad's standard ones).
No problem I think (I've made like 5pcs), it will be not pretty and I will end up with some bodge wires. For some reason drilled holes didn't make it.
So, next thing will be soldering, preparing cartridge connector (30deg), review and checking it on st.

opl3Cart_pcb_proto_rev11.jpeg (499.28 KiB) Viewed 4935 times

[nokturnal]

Ok, so I've made two prototypes, first one ugly due to mistaken footprints (ended up in spiders web)

OPL3 ST cart v1 bottom ugly one

opl3Cart_pcb_proto_rev11_assembled_back.jpeg (344.05 KiB) Viewed 3258 times

and pretty one, which actually has corrected footprints, chiseled 30 degree edge connector and fits into short st.

Here's second one:

st cart opl3 development v.2 pcb

opl3 cart dev proto boards v.2.jpeg (495.04 KiB) Viewed 3261 times

Assembled:

OPL3 ST cart v2 top assembled

opl3_cart_dev_proto_board_v2_top.jpeg (453.37 KiB) Viewed 3261 times

OPL3 ST cart v2 bottom assembled with some bodge wires for debugging

opl3_cart_dev_proto_board_v2_bottom.jpeg (271.63 KiB) Viewed 3261 times

Good news are that:
1) I didn't burn MMU this time in both cases . It's useful ..
2) I wrote driver and checked them with logic analyser. Look ok and i can push vgm data through it like with other opl devices. Is much nicer than any other.

OPL3 ST cart with logic analyzer

st_opl3_cart_interface_la.jpeg (258.34 KiB) Viewed 3256 times

Bad news:
1) Turned out that probably I need another pass on reset circuit,
2) Can't tell if op-amps circuit does what it should.
3) I've got weird output on DAC, so either I have made something wrong or OPL3 / YAC-512-M I've got are fake or damaged for some reason or maybe something is screwed up with opamps I've used (used new type of TL084 - TL084ACP). But I've checked connections with multimeter, and everything looks fine.
Under oscilloscope DAC channel output looks like this and there's no response no matter what is set on datalines (looks like saw):

ST cart proto 2 DAC output

DAC_output_ST_dev_cart_v.2.jpeg (184.02 KiB) Viewed 3261 times

ST cart proto 2 DAC output bigger

DAC_output_ST_dev_cart_v.2_2.jpeg (217.85 KiB) Viewed 3261 times

It's quite different than output from OPL3LPT. Here's like like it looks (behaves like actual audio wave):

DAC output OPL3LPT

DAC_output_OPL3LPT.jpeg (179.57 KiB) Viewed 3261 times

So probably I need to figure out what's causing it and how to diagnose this issue.
I've made some work on OPL2 cart too, it is much simpler. Still need to make some adjustments to pcb, before sending it to manufacturer and find out what's going on with opl3 version, to not repeat same mistakes.

[nokturnal]

ok, everything took me a while. In the meantime I've made ST opl2 cart version, which I've managed to actually use today. Turned out that my drivers were ok, but I've erroneously inverted opl datalines assignment to cart adress bus( ), but I've managed to revert it on driver level. Still there will be another pcb revision. Output is quite noisy,but good enough for prototype.

Here's cart photos, screen from player and sample from DOS Dune recorded from 520st+. I need to check out opl3 version with patched drivers. Maybe it will work..
[edit] apparently opl3 version also works, i swapped there also two opl address lines. Fixed this in driver too ... But this means another pcb revision... Added sample output too...

opl2cart

signal-2024-07-05-231150_002.jpeg (141.47 KiB) Viewed 1722 times

custom vgm player

signal-2024-07-05-231150_003.jpeg (358.62 KiB) Viewed 1722 times

[sporniket]

good work

[nokturnal]

Thanks to everyone for help during process... Still not final version, but pretty good milestone ..

[tOriman]

! GOOD WORK !



tOri

[agranlund]

Very nice!!
I'd definitely be interested in getting one of these for my 520ST.

[nokturnal]

I've recorded several video/audio captures of 520ST+ equipped with my two OPL2 and OPL3 cart prototypes and replayed standard OPL3/OPL2 tune playlists which I've used on other devices.

OPL3cart:




OPL2cart: