ADC application

Use analog voltage inputs to control the motor with a physical throttle or brake lever.

The ADC application reads analog voltages from the COMM header’s ADC1 and ADC2 pins and maps them to a motor output level. It is the standard choice for physical throttle and brake levers that output a voltage proportional to position.

Voltage range

Default voltage mapping from appconf_default.h:

Parameter	Default	Description
voltage_start	0.9 V	Voltage at which throttle output begins.
voltage_end	3.0 V	Voltage at which throttle reaches maximum.
voltage_center	2.0 V	Center voltage for bidirectional control types.
voltage_min	0.0 V	Below this voltage the signal is treated as a fault.
voltage_max	3.5 V	Above this voltage the signal is treated as a fault.
voltage2_start	0.9 V	Start voltage for the second ADC channel (brake).
voltage2_end	3.0 V	End voltage for the second ADC channel (brake).

If the measured voltage falls outside voltage_min–voltage_max, the application treats it as a disconnected sensor and cuts motor output. Ensure your sensor voltage never exceeds 3.3 V on standard VESC hardware.

Control types

typedef enum {
    ADC_CTRL_TYPE_NONE = 0,
    ADC_CTRL_TYPE_CURRENT,
    ADC_CTRL_TYPE_CURRENT_REV_CENTER,
    ADC_CTRL_TYPE_CURRENT_REV_BUTTON,
    ADC_CTRL_TYPE_CURRENT_REV_BUTTON_BRAKE_ADC,
    ADC_CTRL_TYPE_CURRENT_REV_BUTTON_BRAKE_CENTER,
    ADC_CTRL_TYPE_CURRENT_NOREV_BRAKE_CENTER,
    ADC_CTRL_TYPE_CURRENT_NOREV_BRAKE_BUTTON,
    ADC_CTRL_TYPE_CURRENT_NOREV_BRAKE_ADC,
    ADC_CTRL_TYPE_DUTY,
    ADC_CTRL_TYPE_DUTY_REV_CENTER,
    ADC_CTRL_TYPE_DUTY_REV_BUTTON,
    ADC_CTRL_TYPE_PID,
    ADC_CTRL_TYPE_PID_REV_CENTER,
    ADC_CTRL_TYPE_PID_REV_BUTTON
} adc_control_type;

Suffix	Meaning
(none)	Forward only, no brake.
REV_CENTER	Reverse when ADC1 is below center voltage.
REV_BUTTON	Reverse when a dedicated button is pressed.
BRAKE_ADC	Braking current set by ADC2 voltage.
BRAKE_CENTER	Braking when ADC1 is below center voltage.
BRAKE_BUTTON	Braking when a dedicated button is pressed.
NOREV	Forward-only mode regardless of input.

Configuration struct

typedef struct {
    adc_control_type ctrl_type;
    float hyst;
    float voltage_start;
    float voltage_end;
    float voltage_min;
    float voltage_max;
    float voltage_center;
    float voltage2_start;
    float voltage2_end;
    bool use_filter;
    SAFE_START_MODE safe_start;
    uint8_t buttons;
    bool voltage_inverted;
    bool voltage2_inverted;
    float throttle_exp;
    float throttle_exp_brake;
    thr_exp_mode throttle_exp_mode;
    float ramp_time_pos;
    float ramp_time_neg;
    bool multi_esc;
    bool tc;
    float tc_max_diff;
    uint32_t update_rate_hz;
} adc_config;

Key parameters

Field	Default	Description
hyst	0.15	Deadband around center/off point (normalised).
use_filter	true	Applies a moving-average filter over FILTER_SAMPLES (5) readings.
safe_start	SAFE_START_REGULAR	Requires voltage to return to idle range before output is allowed.
update_rate_hz	500 Hz	ADC polling rate.
ramp_time_pos	0.3 s	Positive output ramp time.
ramp_time_neg	0.1 s	Negative output ramp time.
voltage_inverted	false	Inverts ADC1 mapping (full voltage = idle).
voltage2_inverted	false	Inverts ADC2 mapping.
multi_esc	true	Forwards command over CAN bus.

Throttle curve

The throttle_exp and throttle_exp_brake fields tune the exponential response curve, controlled by throttle_exp_mode:

typedef enum {
    THR_EXP_EXPO = 0,
    THR_EXP_NATURAL,
    THR_EXP_POLY
} thr_exp_mode;

A value of 0.0 gives a linear response. Positive values make the initial part of the throttle softer.

Runtime API

void app_adc_start(bool use_rx_tx);
void app_adc_stop(void);
void app_adc_configure(adc_config *conf);
float app_adc_get_decoded_level(void);
float app_adc_get_voltage(void);
float app_adc_get_decoded_level2(void);
float app_adc_get_voltage2(void);
bool app_adc_range_ok(void);
void app_adc_detach_adc(int detach);
void app_adc_adc1_override(float val);
void app_adc_adc2_override(float val);

app_adc_range_ok returns false when either ADC channel voltage is outside the configured min/max bounds, which can be polled to detect a disconnected sensor.