# embedded-patterns

> Embedded C firmware patterns for HAL/driver layering, state machines, ring buffers, and low-level safety practices. Use for MCU firmware architecture and device driver design.

- Author: establers
- Repository: Establers/claude_skills_for_our_team
- Version: 20260124205403
- Stars: 0
- Forks: 0
- Last Updated: 2026-02-06
- Source: https://github.com/Establers/claude_skills_for_our_team
- Web: https://mule.run/skillshub/@@Establers/claude_skills_for_our_team~embedded-patterns:20260124205403

---

---
name: embedded-patterns
description: Embedded C firmware patterns for HAL/driver layering, state machines, ring buffers, and low-level safety practices. Use for MCU firmware architecture and device driver design.
---

# Embedded Firmware Patterns

## HAL / Driver Layering

```c
// hal_spi.h
typedef struct {
  status_t (*write)(const uint8_t *data, size_t len);
  status_t (*read)(uint8_t *data, size_t len);
} hal_spi_t;

// driver uses HAL only
status_t sensor_read_id(const hal_spi_t *spi, uint8_t *out_id) {
  uint8_t cmd = 0x9FU;
  status_t st = spi->write(&cmd, 1U);
  if (st != STATUS_OK) return st;
  return spi->read(out_id, 1U);
}
```

## Finite State Machine

```c
typedef enum { ST_INIT, ST_READY, ST_RUN, ST_FAULT } app_state_t;
static app_state_t state = ST_INIT;

void app_tick(void) {
  switch (state) {
    case ST_INIT:
      if (app_init_ok()) state = ST_READY;
      break;
    case ST_READY:
      if (app_start_requested()) state = ST_RUN;
      break;
    case ST_RUN:
      if (app_fault()) state = ST_FAULT;
      break;
    case ST_FAULT:
      app_handle_fault();
      break;
    default:
      state = ST_FAULT;
      break;
  }
}
```

## Ring Buffer for UART/Logging

```c
typedef struct {
  uint8_t *buf;
  size_t size;
  size_t head;
  size_t tail;
} ringbuf_t;

bool ringbuf_push(ringbuf_t *rb, uint8_t v);
bool ringbuf_pop(ringbuf_t *rb, uint8_t *out);
```

## Error Codes (No Exceptions)

```c
typedef enum {
  STATUS_OK = 0,
  STATUS_INVALID_ARG,
  STATUS_TIMEOUT,
  STATUS_IO_ERROR,
  STATUS_BUSY
} status_t;
```

## Low-Power Pattern

```c
void app_idle_hook(void) {
  // Enter sleep when no work is pending
  if (can_sleep()) {
    enter_sleep_mode();
  }
}
```

**Remember**: Keep ISRs tiny, validate all inputs, and separate hardware access from application logic.