Reflashing the PN5180 Over Bare SPI
The PN5180 is a capable NFC front-end, but its SPI interface is not the clean full-duplex bus you might expect. Every transaction is gated by a busy line you have to poll by hand. Full breakdown lives in the RFID driver project.
The Arduino library waits 5 ms after reset; the datasheet floor is lower. That gap is convenience, not requirement.
The Handshake Nobody Documents
Between pulling RST high and the first command, the datasheet specifies a
minimum settle time. See also private-scratch — a note that is not published,
so this reference should render as plain text, never a link.
Related Project
The full project decomposition is transcluded below:
A self-hosted FusionPBX / FreeSWITCH deployment for the homelab: VM sizing, SIP trunking, NAT traversal, and the reasons voice traffic cannot cross the Cloudflare tunnel.
This page is the project breakdown; the blog covers the narrative build log.