PSA: MiSTer Analog IO Boards with broken SNAC compatibility in the wild
Posted by Michael Flisowski on
For our first ever blog post we're putting out a bit of a PSA regarding SNAC compatibility with certain Analog IO boards being sold on eBay and Aliexpress.
Recently we sold a SNAC adapter with NES/SNES connectors to a customer who intended to use it with their Analog IO board. Unfortunately after much troubleshooting they contacted us saying they couldn't get our SNAC board to work.
We sent out another SNAC board and corresponding NES/SNES adapters in the very unlikely scenario that the components that were sent to this customer were faulty (as we make sure we test everything before sending to our customers). We also went to the effort of sending out a power supply in case the customer's one was at fault.
We also requested some photos of the customer's IO board and what we saw shocked us - a set of header pins were completely missing! We've marked this in the photo below with a red rectangle:
By reviewing the circuit schematic on Github it became obvious what had happened. The USB port where the SNAC board plugs into the IO Board (marked by J4) was not electrically being connected to the female header on the DE-10 Nano (marked by P7). We've highlighted the relevant connections in an excerpt from the schematic below:
Now, we're not ones to slander other creators but in this instance the customer purchased their Analog IO board from AliExpress. Take a close look at the first picture on this listing - note that there are no header pins soldered at all right next to the User USB Port. At the time of writing this post, here's another example on eBay.
Put quite simply:
SNAC Boards will NOT work without those pins being there!
After reviewing listings on eBay and AliExpress it appears that only version 6.0 Analog IO Boards from some sellers are being sold without this header. It's hard to be sure because it is very easy to steal photos from another seller and use them on your listings - we have had this very issue happen on our own eBay store and unfortunately we don't have any solutions to stop this - if you guys have any suggestions we are all ears!
We're not saying that every version 6.0 Analog IO board out there has this issue; far from it. There are plenty of awesome sellers out there in the community who do this as a labour of love, much like us. We understand that sometimes its not possible to have stock of the absolute latest version of each board, but regardless of what version being sold we think its important that it is built properly, by a reputable seller.
If you are specifically needing SNAC compatibility, please double check that the IO Board you are buying has the P7 header soldered on, especially if you are importing a board from overseas where returns may be difficult, and all you have are photos from an advertisement to go off.
In the end the customer purchased a 6.1 Analog IO board from us and this resolved their SNAC issues, so we're happy.
We've got some more material to share but please reach out if you've got any questions - we're here to help!
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The boards being sold on Aliexpress and eBay do not match the official Mister FPGA specifications. You only have to look at the USB v2.1 hubs being sold on these sites to realise this. They are marked as v2.1 but there is no USB port on the pwr1 location on the board.