Atari ST OPL3 cart schematics

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DoG
Posts: 1143
Joined: Sat Apr 07, 2018 12:26 pm

Re: Atari ST OPL3 cart schematics

Post by DoG »

Yes. 1,6mm on 4 or even more layers as well
nokturnal
Posts: 60
Joined: Wed Aug 12, 2020 12:30 pm

Re: Atari ST OPL3 cart schematics

Post by 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.
saulot/[nokturnal]
------------------------
www: https://nokturnal.pl
nokturnal
Posts: 60
Joined: Wed Aug 12, 2020 12:30 pm

Re: Atari ST OPL3 cart schematics

Post by 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
opl3Cart_pcb_proto_rev11.jpeg (499.28 KiB) Viewed 1793 times
saulot/[nokturnal]
------------------------
www: https://nokturnal.pl
nokturnal
Posts: 60
Joined: Wed Aug 12, 2020 12:30 pm

Re: Atari ST OPL3 cart schematics

Post by 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
OPL3 ST cart v1 bottom ugly one
opl3Cart_pcb_proto_rev11_assembled_back.jpeg (344.05 KiB) Viewed 115 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
st cart opl3 development v.2 pcb
opl3 cart dev proto boards v.2.jpeg (495.04 KiB) Viewed 118 times
Assembled:
OPL3 ST cart v2 top assembled
OPL3 ST cart v2 top assembled
opl3_cart_dev_proto_board_v2_top.jpeg (453.37 KiB) Viewed 118 times
OPL3 ST cart v2 bottom assembled with some bodge wires for debugging
OPL3 ST cart v2 bottom assembled with some bodge wires for debugging
opl3_cart_dev_proto_board_v2_bottom.jpeg (271.63 KiB) Viewed 118 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
OPL3 ST cart with logic analyzer
st_opl3_cart_interface_la.jpeg (258.34 KiB) Viewed 113 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
ST cart proto 2 DAC output
DAC_output_ST_dev_cart_v.2.jpeg (184.02 KiB) Viewed 118 times
ST cart proto 2 DAC output bigger
ST cart proto 2 DAC output bigger
DAC_output_ST_dev_cart_v.2_2.jpeg (217.85 KiB) Viewed 118 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
DAC_output_OPL3LPT.jpeg (179.57 KiB) Viewed 118 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.
saulot/[nokturnal]
------------------------
www: https://nokturnal.pl
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