# Bus Debugging

> Diagnose SPI, UART, CAN and I2C protocol failures using transaction evidence and electrical const…

Diagnose SPI, UART, CAN and I2C protocol failures using transaction evidence and electrical constraints. Use when requests involve corrupt bytes, wrong SPI mode, framing, bus-off, chip-select timing or DMA transfers; use I2C bring-up for basic discovery.

- Page: https://ss33.ai/skills/wedsamuel1230/bus-debugging-67209378474
- Publisher: wedsamuel1230
- Category: [Software Development](https://ss33.ai/skills/category/software-development-t44z8z) › [Misc](https://ss33.ai/skills/category/software-development-t44z8z/misc-0pfo0b)
- License: MIT
- Source: https://github.com/wedsamuel1230/embedded-engineering-skills/blob/869710ec3b9a40a4f14615b68ca1f1d3dfc88323/skills/bus-debugging/SKILL.md

## Skill

SKILL.md: https://ss33.ai/api/v1/ss33/download/wedsamuel1230/bus-debugging-67209378474

# Bus Debugging

Read [the shared embedded contract](../../docs/arduino-skill-contract.md) and
keep source/build, device and physical evidence separate.

Read [protocol branches](references/workflow.md). Identify exact controller,
peripheral, voltage domain, pins/mux, clock, transfer mode, payload and capture
point. Separate electrical, framing, driver and application interpretation.
Do not assume a decoded analyzer trace proves voltage margin or signal quality.

Choose a minimal transaction with a datasheet-defined response. Compare the
actual wire capture with the requested byte order, edges, framing and timeout.
For I2C discovery/pull-ups route to `i2c-bringup-diagnostician`; use this skill
for transaction framing and cross-layer diagnosis. Scans/transfers can write
or trigger devices, so keep attached actuators in the required safe state.

For DMA inspect buffer lifetime, alignment/cache coherency where applicable,
completion/error path and concurrent ownership before adding arbitrary delays.
Compare a bounded polling transfer to DMA only when the test is appropriate
and authorized. Keep the failing configuration and change one causal variable.

Deliver annotated expected/observed transaction, evidence location and next
check. Distinguish MCU peripheral errors, analyzer decoding assumptions and
what remains electrically unmeasured.

See [platform coverage](../../docs/platform-support.md) for the exact tested
combination. A source procedure is not a claim that every target was tested.