> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/vedderb/bldc/llms.txt
> Use this file to discover all available pages before exploring further.

# Supported encoders

> Reference for all encoder types supported by the VESC firmware, including interface details and diagnostic fields.

The VESC firmware supports ten encoder driver families, each implemented as a standalone module under `encoder/`. All drivers expose at minimum an `init`, `deinit`, and angle-read function. The encoder core in `encoder.c` selects and wraps the active driver based on the motor configuration.

The active driver is identified by the `encoder_type_t` enum defined in `encoder_datatype.h`:

```c theme={null}
typedef enum {
    ENCODER_TYPE_NONE = 0,
    ENCODER_TYPE_AS504x,
    ENCODER_TYPE_MT6816,
    ENCODER_TYPE_TLE5012,
    ENCODER_TYPE_AD2S1205_SPI,
    ENCODER_TYPE_SINCOS,
    ENCODER_TYPE_TS5700N8501,
    ENCODER_TYPE_ABI,
    ENCODER_TYPE_AS5x47U,
    ENCODER_TYPE_BISSC,
    ENCODER_TYPE_CUSTOM,
    ENCODER_TYPE_PWM,
    ENCODER_TYPE_PWM_ABI,
    ENCODER_TYPE_MA782,
} encoder_type_t;
```

***

## ABI — `enc_abi`

ABI (A/B/Index) is the standard incremental quadrature encoder interface. Channels A and B produce 90°-offset square waves; counting transitions gives position. The optional Index (I) pulse fires once per revolution and is used to establish an absolute reference.

| Property         | Value                                      |
| ---------------- | ------------------------------------------ |
| Interface        | GPIO (hardware timer quadrature decode)    |
| Resolution       | Configurable (counts per revolution)       |
| Absolute         | No — relative only until index pulse       |
| `encoder_type_t` | `ENCODER_TYPE_ABI`, `ENCODER_TYPE_PWM_ABI` |

**Key state fields** (`ABI_state`):

```c theme={null}
typedef struct {
    volatile bool     index_found;
    volatile uint32_t cnt_at_ind_last;
    volatile int      bad_pulses;
    volatile uint32_t index_pulse_cnt;
} ABI_state;
```

<Tip>
  Call `encoder_index_found()` to check whether the firmware has seen the index pulse after power-on. FOC accuracy improves once the index is found.
</Tip>

***

## AS504x — `enc_as504x`

The AS504x family (AS5040, AS5045, AS5047, AS5048) from ams-OSRAM are contactless magnetic rotary position sensors that communicate over SPI using a bit-bang software SPI (`spi_bb`).

| Property         | Value                   |
| ---------------- | ----------------------- |
| Interface        | SPI (software bit-bang) |
| Resolution       | Up to 14-bit (AS5048)   |
| Absolute         | Yes — single-turn       |
| `encoder_type_t` | `ENCODER_TYPE_AS504x`   |

**Diagnostic fields** (`AS504x_diag`):

```c theme={null}
typedef struct {
    uint8_t  is_connected;
    uint8_t  AGC_value;       // Automatic gain control
    uint16_t magnitude;       // Field magnitude
    uint8_t  is_OCF;          // Offset compensation finished
    uint8_t  is_COF;          // Cordic overflow — magnet too close/far
    uint8_t  is_Comp_low;     // AGC at maximum — magnet too far
    uint8_t  is_Comp_high;    // AGC at minimum — magnet too close
    ...
} AS504x_diag;
```

Monitor `is_COF`, `is_Comp_low`, and `is_Comp_high` to verify correct airgap between the sensor and the diametrically magnetised target magnet.

***

## AS5x47U — `enc_as5x47u`

The AS5x47U family (e.g., AS5047U, AS5147U) are high-speed magnetic rotary encoders from ams-OSRAM with hardware SPI and an extended diagnostic register set.

| Property         | Value                  |
| ---------------- | ---------------------- |
| Interface        | SPI (hardware)         |
| Resolution       | Up to 14-bit           |
| Absolute         | Yes — single-turn      |
| `encoder_type_t` | `ENCODER_TYPE_AS5x47U` |

**Diagnostic fields** (`AS5x47U_diag`) include watchdog test status (`is_wdtst`), CRC error flag (`is_crc_error`), broken Hall flag (`is_broken_hall`), and field half-strength flag (`is_mag_half`), in addition to the same AGC and magnitude fields as the AS504x.

***

## BiSS-C — `enc_bissc`

BiSS-C (Bidirectional Serial Synchronous Communication) is an open-standard serial interface for absolute encoders and other sensors. The firmware uses hardware SPI and a 6-bit CRC to validate each frame.

| Property         | Value                                          |
| ---------------- | ---------------------------------------------- |
| Interface        | SPI (hardware)                                 |
| Resolution       | Configurable (`enc_res` field)                 |
| Absolute         | Yes — single or multi-turn depending on sensor |
| `encoder_type_t` | `ENCODER_TYPE_BISSC`                           |

**Key state fields** (`BISSC_state`):

```c theme={null}
typedef struct {
    float    spi_data_error_rate;
    uint32_t spi_data_error_cnt;
    float    spi_comm_error_rate;
    uint32_t spi_comm_error_cnt;
    float    last_enc_angle;
    uint32_t spi_val;
    uint32_t last_update_time;
    uint8_t  decod_buf[8];
} BISSC_state;
```

***

## MA782 — `enc_ma782`

The MagAlpha MA782 from Monolithic Power Systems is a high-speed contactless angle sensor with an SPI interface and an internal angle tracking register.

| Property         | Value                                      |
| ---------------- | ------------------------------------------ |
| Interface        | SPI (hardware)                             |
| Resolution       | 8-bit to 16-bit depending on configuration |
| Absolute         | Yes — single-turn                          |
| `encoder_type_t` | `ENCODER_TYPE_MA782`                       |

The driver uses an asynchronous state machine (`ma782_substate_t`) with `MA782_IDLE` and `MA782_READ_ANGLE_REQ` states to pipeline SPI transfers with the FOC interrupt.

**Error flags** (`ma782_error_t`):

```c theme={null}
typedef enum {
    MA782_CALLBACK_IN_IDLE   = 1 << 0,
    MA782_SPI_ERROR          = 1 << 1,
    MA782_READ_NOT_IDLE      = 1 << 2,
    MA782_SPI_NOT_READY      = 1 << 3,
    MA782_ANGLE_NOT_IDLE     = 1 << 4,
    MA782_UNKNOWN_STATE      = 1 << 5,
    MA782_WRITE_NOT_IDLE     = 1 << 6,
    MA782_WRITE_REG_FAIL     = 1 << 7,
    MA782_WRITE_READOUT_FAIL = 1 << 8,
} ma782_error_t;
```

***

## MT6816 — `enc_mt6816`

The MT6816 from MagnTek is a 14-bit contactless magnetic angle sensor with hardware SPI and a no-magnet detection flag.

| Property         | Value                 |
| ---------------- | --------------------- |
| Interface        | SPI (hardware)        |
| Resolution       | 14-bit                |
| Absolute         | Yes — single-turn     |
| `encoder_type_t` | `ENCODER_TYPE_MT6816` |

**Key state fields** (`MT6816_state`):

```c theme={null}
typedef struct {
    float    spi_error_rate;
    float    encoder_no_magnet_error_rate;
    uint32_t encoder_no_magnet_error_cnt;  // Magnet absent or too weak
    float    last_enc_angle;
    uint32_t spi_error_cnt;
    uint32_t spi_val;
    uint32_t last_update_time;
} MT6816_state;
```

<Warning>
  Non-zero `encoder_no_magnet_error_cnt` indicates the target magnet is missing or the airgap is too large. Do not run FOC in this condition.
</Warning>

***

## PWM — `enc_pwm`

Some encoder and position-sensor modules output angle as a PWM duty cycle (e.g., AS5600 in PWM mode). The `enc_pwm` driver captures the duty cycle using a timer input-capture peripheral and converts it to degrees.

| Property         | Value                                         |
| ---------------- | --------------------------------------------- |
| Interface        | PWM input (hardware timer)                    |
| Resolution       | Duty-cycle resolution of the source sensor    |
| Absolute         | Yes — single-turn (limited by PWM resolution) |
| `encoder_type_t` | `ENCODER_TYPE_PWM`, `ENCODER_TYPE_PWM_ABI`    |

The `ENCODER_TYPE_PWM_ABI` variant combines PWM absolute position with ABI quadrature for higher update rates.

***

## SinCos — `enc_sincos`

Analogue sine/cosine encoders output two 90°-phase-shifted analogue signals. The firmware reads these on ADC channels, applies gain and offset calibration, and computes the angle with `atan2`.

| Property         | Value                                             |
| ---------------- | ------------------------------------------------- |
| Interface        | Analogue (ADC)                                    |
| Resolution       | Determined by ADC resolution and signal quality   |
| Absolute         | Within one period — multi-pole pairs expand range |
| `encoder_type_t` | `ENCODER_TYPE_SINCOS`                             |

**Configuration** (`ENCSINCOS_config_t`) exposes gain (`s_gain`, `c_gain`), offset (`s_offset`, `c_offset`), a low-pass `filter_constant`, and a `phase_correction` angle to compensate for mechanical misalignment between the sine and cosine tracks.

***

## TLE5012 — `enc_tle5012`

The TLE5012B from Infineon is a magnetic angle sensor with a proprietary SSC (Synchronous Serial Communication) interface that is compatible with software SPI.

| Property         | Value                         |
| ---------------- | ----------------------------- |
| Interface        | SSC / SPI (software bit-bang) |
| Resolution       | 15-bit                        |
| Absolute         | Yes — single-turn             |
| `encoder_type_t` | `ENCODER_TYPE_TLE5012`        |

**Error types** (`tle5012_errortypes`):

```c theme={null}
typedef enum tle5012_errortypes {
    NO_ERROR               = 0x00,
    SYSTEM_ERROR           = 0x01,  // Over/under voltage, no magnet, ROM defect
    INTERFACE_ACCESS_ERROR = 0x02,  // Wrong address or lock
    INVALID_ANGLE_ERROR    = 0x04,  // GMR element failure
    ANGLE_SPEED_ERROR      = 0x08,  // Angular speed calculation error
    CRC_ERROR              = 0xFF,  // CRC mismatch
} tle5012_errortypes;
```

***

## TS5700N8501 — `enc_ts5700n8501`

The TS5700N8501 from Tamagawa Seiki is a serial absolute encoder commonly found on industrial servo motors. It communicates over a UART-based serial interface and provides both single-turn and multi-turn (ABM) position.

| Property         | Value                                          |
| ---------------- | ---------------------------------------------- |
| Interface        | UART (serial)                                  |
| Resolution       | 17-bit single-turn                             |
| Absolute         | Yes — single-turn and multi-turn (ABM counter) |
| `encoder_type_t` | `ENCODER_TYPE_TS5700N8501`                     |

The multi-turn counter is readable via `enc_ts5700n8501_get_abm()` and can be reset with `enc_ts5700n8501_reset_multiturn()`.

```c theme={null}
// Read the 16-bit multi-turn (ABM) counter
int16_t abm = enc_ts5700n8501_get_abm(&cfg);

// Reset multi-turn counter
enc_ts5700n8501_reset_multiturn(&cfg);
```

<Note>
  The TS5700N8501 runs its communication in a dedicated ChibiOS thread due to the UART timing requirements. The raw 8-byte status frame is available at `cfg.state.raw_status` for advanced diagnostics.
</Note>

***

## Implementing a custom encoder

If none of the built-in drivers match your hardware, the encoder system supports a custom callback interface:

```c theme={null}
// encoder.h
void encoder_set_custom_callbacks(
    float  (*read_deg)(void),
    bool   (*has_fault)(void),
    char * (*print_info)(void)
);
```

Set `encoder_type_t` to `ENCODER_TYPE_CUSTOM` in the motor configuration and register your three callbacks. The FOC loop will call `read_deg()` on every current-control cycle.