encoder_driver.c File Reference

High-level routines for initializing and reading a rotary encoder. More...

#include "encoder_driver.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include "stm32f4xx_hal.h"

Macros
#define	STALL_THRESHOLD   5
#define	STALL_COUNT   20
#define	STALL_DELAY_MS   10

Functions
void	setup_encoder (encoder_t *p_enc)
	Initialize encoder state.
void	read_encoder (encoder_t *p_enc)
	Read and accumulate encoder ticks since last call.
void	wait_for_stall (encoder_t *p_enc)
	Waits until the encoder motion stalls (no significant ticks change).

Detailed Description

High-level routines for initializing and reading a rotary encoder.

Created on: Jun 7, 2025 Author: Andrew Carr and Kai De La Cruz

Function Documentation

read_encoder()

void read_encoder

(

encoder_t *

p_enc

)

Read and accumulate encoder ticks since last call.

Reads encoder ticks and applies wrap-around correction.

Parameters

p_enc

Pointer to an encoder_t instance.

Computes the difference between the current timer count and the zero reference, applies wrap-around correction based on the encoder’s auto-reload value (p_enc->ar), and updates:

• last_ticks: snapshot of this read
• ticks: cumulative total (signed)

Wrap-around logic: If the delta exceeds half the auto-reload range, it is adjusted by ±(ar+1) to account for rollover.

setup_encoder()

void setup_encoder

(

encoder_t *

p_enc

)

Initialize encoder state.

Initializes the encoder by setting its zero reference.

Parameters

p_enc

Pointer to an encoder_t instance.

Captures the current hardware timer counter as the zero reference, and clears both the cumulative tick count and the last-read snapshot.

wait_for_stall()

void wait_for_stall

(

encoder_t *

p_enc

)

Waits until the encoder motion stalls (no significant ticks change).

Parameters

p_enc

Pointer to encoder_t instance