Akai DPS24 ADAT expansion card woes: no audio

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Re: Akai DPS24 ADAT expansion card woes: no audio

Post by Anthony gilbert »

Coz,

Many thanks for your detailed appraisal of the fault - and my apologies for taking so long to reply (a very busy start to 2022).

I have performed only basic tests on the expansion board, but it does appear to have the 5v, 3v3 and 2.5v rails working. I also have the schematics.

I haven't yet had chance to hook up my data analyser to look at the SPI messaging. I'm not convinced it will uncover anything that I can compare to what a working solution - perhaps some basic handshaking, but given the main DPS24 menus acknowledge the ADAT expansion, I'm guessing this initially works.

Testing my ADAT expansion on another DPS24 still appears to be the most logical step. The FPGA is on a socket, so my original programmed version could be copied/tested on your expansion card - that in itself sounds like it could be useful for your situation. I shall try to send a private message with my email now...
Anthony gilbert
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Posts: 15 Joined: Wed Dec 23, 2020 10:17 am

Re: Akai DPS24 ADAT expansion card woes: no audio

Post by Anthony gilbert »

Keen to further investigate the provision of power to the ADAT expansion card, so here's an update:

The Expansion ADAT GP1F32T (TOSLINK Transmitter) LEDs switch off after initial boot-up, which seems contrary to what other people are experiencing. Is this a result of the expansion card itself being powered down, post-boot?

In short, it appears not.

For one, the schematics suggest the DPS24 doesn't have a modular set of 5v supply rails for option cards. Next, I have added a breakout to the 9-pin ADAT sync D-Sub. This proves the ongoing existence of the 5v rail, as well as some periodic serial-out on pin-9. Interestingly, this serial-out data first passes through an AND gate with a PWRGDB as the enable. PWRGDB (Power Good) appears to work as a general enabler across several external facing I/O including the MIDI jack. The use of "Power Good" is used in other Akai products, and seems to rule out the idea of high power consumption (failing component) shutting options off.

So, we have 5v power, component tested 3v3 and 2v5 regulators, expansion board system recognition (handshake) on boot, PWRGDB enabled, and the FPGA pin 139 generating serial streams to the 9-pin ADAT SYNC D-Sub.

The expansion board on the face of it appears healthy, but with the transmitter LEDs still going off after c. 5 seconds from boot. They are controlled directly from the FPGA pins 117, 118. Puzzling, but more investigation to follow.

P.S, made an error in a previous reply when I called the socketed IC the FPGA. It is merely a generic array logic IC.
Anthony gilbert
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Posts: 15 Joined: Wed Dec 23, 2020 10:17 am
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