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Optional XIAO CAN interface

Hardware: official Seeed XIAO CAN Bus Expansion Board, SKU 105100001, MCP2515 controller with 16 MHz crystal and SN65HVD230 3.3 V transceiver.

XIAO pin ESP32-S3 GPIO CAN function IR conflict
D6 43 MCP2515 INT none
D7 44 MCP2515 CS none
D8 7 SPI SCK none
D9 8 SPI MISO none
D10 9 SPI MOSI none
D0 1 IR RMT TX CAN unused
D1 2 IR RMT RX CAN unused

Default CAN bitrate: 500 kbit/s. SPI: 10 MHz, mode 0. Compile-time _Static_assert checks prevent future IR/CAN pin overlap.

Interfaces:

  • ir_spoke_can: portable frame encoding and caller-supplied send callback.
  • ir_spoke_can_mcp2515_adapter: ESP-IDF spi_master and MCP2515 register protocol for the official board.
  • ir_spoke_rmt_adapter: publishes one estimate frame after each accepted blockage when the CAN publisher is enabled.

Standard ID 0x180 payload:

Byte Field Encoding
0 inferred spoke count unsigned
1 current spoke index unsigned
2–3 wheel frequency little-endian mHz
4–5 blockage duration little-endian µs
6–7 confidence little-endian per mille

config/system.json is authoritative. tools/generate_constants.py writes the pin map, oscillator, bitrate, SPI clock, enable default and CAN ID into firmware and SPICE constants. The localhost simulator exposes CAN enable and bus-duty inputs and plots can_current_ma.

Official sources and Zotero keys are recorded in docs/zotero_links.json.