hx711 v0.1.0

HX711 24-bit load-cell amplifier.

Application scenarios

• A kitchen or platform scale.
• A force or torque sensor.
• A tension controller.

Contract

uint8_t hx711_init(hx711_t *device, hx711_port_t port);
uint8_t hx711_ready(hx711_t *device);
uint8_t hx711_read(hx711_t *device, int32_t *value);

• read waits for DOUT low, clocks 24 bits, then sends the gain pulses.
• Gain 128 selects channel A; gain 64 selects channel A at 64; gain 32

selects channel B.

• Returns 1 on success, 0 on a timeout.
• The result is sign-extended 24-bit raw data.

Parameters

• Set gain to 128, 64, or 32 before a read; it applies to the next sample.
• The clock high time must stay below 60 us.
• A load-cell excitation of 5 V and a known mV/V rating are needed to scale.

Memory and timing

• About 8 bytes; one read takes 24 clock pulses plus 1..3 gain pulses.
• The conversion rate is 10 or 80 samples/s depending on the module.

Integration

hx711_t scale;
hx711_init(&scale, board_hx711_port());
scale.gain = 128;
int32_t raw;
if (hx711_read(&scale, &raw)) {
    weight = (raw - offset) / scale_factor;
}

Adapters

• The adapter reads DOUT and drives SCK; do not stretch a clock pulse.
• Reference: bogde/HX711 (MIT) and the Avia HX711 datasheet.
• This implementation is original.

When not to use

• A load cell with an SPI ADC; use that converter.
• A high-vibration environment without mechanical filtering.

Verification

make test covers a positive value, a negative value, gain pulses, and a

timeout.

void *context;
uint8_t (*read_dout)(void *context);
void (*set_sck)(void *context, uint8_t level);
void (*delay_us)(void *context, uint16_t microseconds);

hx711_port_t port;
uint8_t gain;