I've been contemplating trying to create a point to point network link between a pair of Pi 4 boards over SPI, as a private network link for a two node cluster. I'm aware of the SPI 10 base T Ethernet interfaces, but was thinking it might be possible to just do it directly over SPI. If I'm reading the BCM2835 SPI chapter correctly, only SPI master is supported on that controller; so I was thinking of possibly implementing it as a Pi-Pico-Pi link, with a Pico in the middle as a dual SPI slave buffering between the two SPI busses. That would also potentially let me use the Pico as a cluster STONITH device to allow each Pi to interrupt power to the other Pi. (This is for a corosync/pacemaker type cluster.)
I thought about using HDLC (ISO/IEC 13239), but it has some requirements to handle data at the bit level, to escape flag sequences in the bitstream, where the BCM2835 SPI controller seems to be primarily byte oriented. PPP has a suitable alternative (RFC1662), offering HDLC-like synchronous full duplex operation with the option to use octet-stuffing instead of bit-stuffing (thereby making it more suitable for a byte-oriented controller).
I'm just curious if anyone has attempted such a thing, or seen such a thing being done? I.e. linking a pair of Pi boards over SPI, and running something like HDLC or PPP over the serial link, without resorting to just using SPI-to-Ethernet interfaces.
I thought about using HDLC (ISO/IEC 13239), but it has some requirements to handle data at the bit level, to escape flag sequences in the bitstream, where the BCM2835 SPI controller seems to be primarily byte oriented. PPP has a suitable alternative (RFC1662), offering HDLC-like synchronous full duplex operation with the option to use octet-stuffing instead of bit-stuffing (thereby making it more suitable for a byte-oriented controller).
I'm just curious if anyone has attempted such a thing, or seen such a thing being done? I.e. linking a pair of Pi boards over SPI, and running something like HDLC or PPP over the serial link, without resorting to just using SPI-to-Ethernet interfaces.
Statistics: Posted by Murph9000 — Wed Aug 14, 2024 12:31 pm — Replies 0 — Views 27