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spi-i2c-baremetal

Use when implementing SPI/I2C master transfers, register read/write protocols, I2C START/STOP, clock phase/polarity, or bus stalls on bare-metal MCUs. Not for Linux drivers: use device-drivers.

.devin/skills/spi-i2c-baremetal/SKILL.md

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Last checked
Nov 4, 2026

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Repository last updated
Sep 28, 2026
License
Apache-2.0

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# SPI and I2C on bare metal

## Contract

| Field | Bound contract |
|---|---|
| Trigger | A sensor, flash, or display must be driven over SPI or I2C without a HAL, a device NACKs or the bus sticks, or a HAL transfer is being replaced with register-level code. |
| Authority | Read-only: emits configuration, transaction sequences, and recovery procedures to chat; the user places them in the firmware. Rollback is not needed because no file is written. No remote mutation. |
| Side effect | Chat output only. |
| Done | The bus clock, mode (SPI phase and polarity or I2C speed), and pin configuration match the slave datasheet, one register read transaction is written flag by flag from the MCU reference manual, and the bus-stuck recovery is stated. |

## Inputs

- Target MCU and its SPI or I2C peripheral version (STM32 I2C v1 on F1 and F4 with `SR1`/`SR2`; I2C v2 on F0, F3, L4, G0, G4 with `CR2` and `ISR`).