On Donnerstag, 17. März 2022 21:52:07 CET Shawn Walker wrote: > Thanks for the links, but based on information in those links it appears > that in USB1.1 the Bulk Endpoints only support 64B transfers (you need USB > 2.0 to reach 512). The rp2040 indicates 1023B for Isoch and 64B for all > others but I could be misreading things... > > I think I'm already getting 64B transfers with serial CDC because when I > send >64B to the TUD interface I see the available bytes go down in groups > of 64 bytes at a time. > I have demonstrated sustained 600KB/sec (4.8Mbps) transfer rates using > serial CDC. USB 1.1 will at best be 9.6Mbit/sec due to 8b/10b encoding, > and likely much worse when you account for delays in switching between > host/device etc.
USB uses Bitstuffing, not 8b10b encoding. Significant parts of the bandwidth are used by the protocol overhead: - BULK IN request from the host (35 bit + interpacket gap) - DATA from the device (35 bit + Payload + interpacket gap) - ACK from the host (19 bit) This sums up to ~12 bytes of protocol overhead for a transfer of up to 64 byte. Regards, Stefan -- Stefan Brüns / Bergstraße 21 / 52062 Aachen home: +49 241 53809034 mobile: +49 151 50412019
signature.asc
Description: This is a digitally signed message part.
_______________________________________________ sigrok-devel mailing list sigrok-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/sigrok-devel
