steami: Add config zone in F103 internal flash gap

[nedseb]

Summary

Closes #2

Adds 3 new I2C commands to read/write a 1 KB config zone stored in the STM32F103 internal flash (gap between bootloader and interface firmware at 0x0800BC00).

Command	Code	Payload	Description
WRITE_CONFIG	0x30	offset(2) + len(1) + data(N)	Write to config zone (read-modify-write)
READ_CONFIG	0x31	offset(2)	Read 256 bytes from config zone
CLEAR_CONFIG	0x32	none	Erase the entire 1 KB config zone

Key properties

• Survives firmware updates: the gap is between bootloader (never touched) and interface (reflashed by user)
• Survives clear_flash: data file erase does not affect the config zone
• No USB crash risk: uses internal flash (not W25Q64 SPI), no bus contention with DAPLink VFS
• Instant reads: config zone is memory-mapped, read is a simple memcpy
• Atomic writes: erase + program in a single operation with shadow buffer to preserve existing data

Files changed

• steami_config.c/.h — new: internal flash config zone driver
• steami_i2c.c/.h — register new commands in is_command_valid() and get_argument_byte_number()
• steami32.c — add task handlers and I2C command documentation

Use cases

• Board revision number (for screen driver selection)
• Board name (classroom identification)
• Sensor calibration data (temperature, magnetometer, accelerometer)
• Boot counter

Test plan

• CLEAR_CONFIG erases zone (all 0xFF)
• WRITE_CONFIG + READ_CONFIG round-trip
• Write at arbitrary offset
• Write preserves existing data (read-modify-write)
• clear_flash does NOT erase config
• Read second 256-byte page
• Large write (28 bytes)
• Multiple sequential writes
• Existing flash operations (READ_SECTOR, WHO_AM_I) still work
• USB stability after 10 write/read stress cycles

[Copilot]

Pull request overview

Adds an internal-flash “config zone” for the STeaMi STM32F103 interface firmware and exposes it over the existing I2C command protocol, using the 1KB BL/IF gap at 0x0800BC00.

Changes:

• Introduces a new internal-flash config driver (steami_config_*) to read/write/erase a 1KB page.
• Adds three new I2C commands (WRITE_CONFIG/READ_CONFIG/CLEAR_CONFIG) to the command enum, validation, and argument sizing.
• Implements new task handlers and updates the I2C command documentation in steami32.c.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
source/board/steami/steami_i2c.h	Adds new I2C command IDs for config operations.
source/board/steami/steami_i2c.c	Registers new commands as valid and defines their fixed argument lengths.
source/board/steami/steami_config.h	Defines config zone address/size and the public read/write/erase API.
source/board/steami/steami_config.c	Implements internal flash read-modify-write and page erase for the config zone.
source/board/steami/steami32.c	Wires new commands into the command handler/task loop and documents them.

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[nedseb]

All 4 review comments addressed in 9bc76dd:

1. Command table — Updated WRITE_CONFIG to document fixed 31-byte payload (offset 2B + len 1B + data max 28B, zero-padded).

2. Silent truncation — WRITE_CONFIG now rejects with bad_parameter error when data_len exceeds available payload instead of silently truncating.

3. Hard-coded constants — STEAMI_CONFIG_ADDR and STEAMI_CONFIG_SIZE now derived from daplink_addr.h macros (DAPLINK_ROM_BL_START + DAPLINK_ROM_BL_SIZE and DAPLINK_SECTOR_SIZE). Added _Static_assert to verify no overlap with interface firmware.

4. Issue steami: Add config zone in F103 internal flash gap. #2 mismatch — Issue steami: Add config zone in F103 internal flash gap. #2 has been updated to reflect the internal flash implementation instead of W25Q64.

[nedseb]

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[nedseb]

Fixed in 76ace49. Replaced _Static_assert (C11) with COMPILER_ASSERT macro from compiler.h for C99 compatibility.