3.3V limitation #3
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Hello again, First of all, hope there have been updates, as I see this repo hasn’t been updated in months… I took note of the 3.3V limitation for this project at this time, and since I see no updates about support for 5V, which apparently goes for most Roland synths, I feel it best to ask: since the official SRX cards do support 5V, is it possible to rewrite one of those cards in the meantime? I noted that 5V isn’t supported due to the modern components needed for a new card, so surely using old ones are an adequate workaround for now? I already have an XV3080 and two SRX cards for testing if this is an option. Thanks again in advance. |
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Replies: 4 comments 2 replies
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Addendum: partially but not solely because of this project, I'm considering selling my XV-3080 in favor of an XV-5050. That said, if I read the service notes correctly, the switch to 3.3V may have started as early as that unit. The internal mask ROM's definitely use the same series of chips as the known-to-work Fantom XR. Since I'm pretty sure the 5050 is also Roland's first synth to support only SRX and not SR-JV, there is a chance that the 5V aspect would only be important both for general conformance and in order to work in the earliest two SRX synths, namely, the 3080 and 5080, and part of me thinks it's related to the fact that both models DO support SR-JV80 ROM's as well. Attached is a screenshot from said 5050 service notes. 
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Yes, supporting 5V is important. I do have a XV5080 as well purchased for testing purposes. I want to do this at some point and I have looked into it somewhat, but what I need is a bit of circuitry allowing both voltages from a single pin that I don't know yet exactly how it works (basic electronic design is something I have picked up along the way, self taught). Something along the lines of a zener diode with a low breakdown voltage and small p-channel mosfets for switching between 3.3V and 5.V I think. Just putting LDOs and voltge levelers for the address and data pins on the cards for a specific 5V version won't help as the programmer is designed for 3.3V and in my opinion, it doesn't make sense to have two programmers with differing programmer firmwares. That would make things too complicated. At the moment, other projects have taken over priority unfortunately. I might pick up on this in a few months. About the 5050: on page 24 of the services notes (Circuit Diagram (Main 4/7)), there are the CN6 and CN7 connectors in more detail on the right hand side. Yes, it seems to be 3.3V for the main flash ICs. The 5V only go into that secondary microwire flash eeprom (Microchip 93LC46 I think I read my notes from earlier correctly) of which I still don't know what it's even used for. I have dumped like two of those and they were always empty. As a result, I haven't even bothered to solder them onto my card and it still works perfectly. |
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Thanks for the response, first of all. Was nervous you were so caught up with the other matters you mention that I’d need to wait longer. The explanation about the voltages does make sense, and it’s a shame that the programmer only supports 3.3V too. Does that mean it’ll have the same effect if I use an official SRX board instead? That was the question I was originally asking in a roundabout way. |
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Ah, no, you cannot use original SRX boards and reprogram them. The reason is that there is a write protect pin on the flash ICs that isn't wired to the JAE connector that connects the SRX card to the mainboard of the synth. My boards and programmers have a secondary connector on them that allows to set this write protect pin to on or off. As a result, the original SRX cards are always write protected.
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Ah, thanks for clarifying. All the more reason to save up for a 5050, or at least trade my 3080 for one, for now then. |
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Patiently waiting for 5V version as well. Just can't justify buying XR unit those days, already have 5080 and 2020. Hope, you'll have some time to work on that. I'm totally fine if it's a separate programmer for 5V logic and 5V card version won't support 3.3V operation. |
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Ah, no, you cannot use original SRX boards and reprogram them. The reason is that there is a write protect pin on the flash ICs that isn't wired to the JAE connector that connects the SRX card to the mainboard of the synth. My boards and programmers have a secondary connector on them that allows to set this write protect pin to on or off. As a result, the original SRX cards are always write protected.