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Originally Posted by alexh
I was more meaning it's not probably not worth trying to do USB2.0 "High-Speed".
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Well Full Speed is only ~1.2MB/s which is well within the capabilities of the Amiga's PCMCIA port, while High Speed is up to ~48MB/s which is well beyond it. But the point is that later devices are still required to support lower speed operation so it's not necessary to support the highest speeds. A High Speed USB 2 controller might require a 30MHz 16 bit bus for maximum continuous throughput, but would still be faster than Full Speed on the Amiga even if it has to slow down to 3.5MHz.
For the zip 250 USBPCM (subject of this thread) full speed should be fast enough because the drive itself can't even manage 1MB/s.
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If you could find some Transdimension UHC124s anywhere, the Subway driver I *believe* was open-sourced together with the source code of Poseidon (the Amiga USB stack)
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That's good to know. I found a Github repository for the Poseidon driver, then discovered that during the last few days Github has become incompatible with my PC! I wonder if I can download it with IBrowse? If not then I will have to crank up the Linux box...
I am thinking an MCU solution like
this might be a better bet. Some PIC24 and PC32 MCUs have a parallel slave port that could be interfaced directly to the PCMICA bus for data transfer and commands, with the MCU taking care of low level USB stuff. Alternatively an STM32 or other MCU with USB host capability could be used with a few latch/buffer interface chips (might want to do this anyway to get 16 bit transfers). Other peripheral ports in the MCU such as SPI, I2C, and GPIO could also be brought out for other purposes. MCU firmware updates could be installed via a separate header and/or through a bootloader controlled by the Amiga.
Advantages of this solution include not being tied to a particular USB host chip that may become obsolete, and reducing CPU load on the Amiga (which only has to send high level commands and transfer data). I have been thinking about producing something like this to replace the CH376, which has a few annoying limitations and (again) may not be available forever.