adc-sampler v0.1.0

Average N ADC reads on a channel.

Application scenarios

• Battery voltage and temperature measurements.
• A sensor channel with white noise where one average is enough.
• A low-end MCU that has no hardware oversampling.

Contract

typedef struct {
    void *context;
    uint16_t (*read)(void *context, uint8_t channel);
} adc_port_t;

void adc_sampler_init(adc_sampler_t *adc, adc_port_t port, uint8_t samples);
uint16_t adc_sampler_read(adc_sampler_t *adc, uint8_t channel);
uint32_t adc_sampler_mv(const adc_sampler_t *adc, uint16_t raw, uint8_t bits, uint32_t vref_mv);

• samples is 1..255; zero becomes one.
• The average is rounded to the nearest integer.
• adc_sampler_mv converts a raw code to millivolts.
• No allocation.

Parameters

• More samples: less noise, more time. 4..16 is common.
• Pair with median or trimmed-mean when spikes exist.

Memory and timing

• 12 bytes of state plus the port context.
• N reads plus one divide; the adapter decides sample time.

Integration

adc_sampler_t battery;
adc_sampler_init(&battery, board_adc_port(), 8);
uint16_t raw = adc_sampler_read(&battery, 0);
uint32_t mv = adc_sampler_mv(&battery, raw, 12, 3300);

Adapters

• Keep channel setup, reference selection, and sample timing in the adapter.
• Reference examples: vendor ADC demos.
• Do not put vendor SFR writes in the core.

When not to use

• Impulses matter; use median or trimmed-mean before averaging.
• A hardware oversampling unit already does this; read its result directly.

Verification

make test covers averaging, rounding, zero samples, and millivolt conversion.

adc_port_t port;
uint8_t samples;