Nanoshield_LoadCell

This is an Arduino library to measure weight using load cells reawith the ADS1230 IC from Texas Instruments.

• Source code: https://github.com/circuitar/Nanoshield_LoadCell
• Documentation: http://nanoshield-loadcell.readthedocs.org/
• Reference board: LoadCell Nanoshield from Circuitar

Library features include:

• Conversion to weight units, based on load cell capacity and sensitivity
• Moving average filter, with configurable number of samples
• Set zero weight point (tare)
• Get measurement in weight units or raw 20-bit value
• Continuous sampling using hardware timer (Timer 2)
• ADS1230 offset calibration

Note: this library uses Timer 2 on the ATmega microcontroller, or Timer 5 on ATmega2560 and ATmega1280. On ATmega168 and ATmega328 (i.e. Arduino UNO or similar), usage of this library will interfere with the tone() function.

To install, just click Download ZIP and install it using Sketch > Include Library... > Add .ZIP Library in the Arduino IDE.

The following examples are provided:

• ReadWeight shows how to do a simple weight measurement using a load cell.
• LcdDigitalWeightScale a digital weight scale using a load cell and an LCD display.
• MultiWeight shows how to read more than one weight using multiple load cells.
• ReadRawValue reads the raw 20-bit integer value from the ADS1230 IC.
• ReadWeightNoAveraging reads weight without averaging (default is to average the last 10 samples).
• ReadWeightLowGain uses low gain to measure a wider weight range.
• OffsetCalibration shows how to use offset calibration.

Class Documentation

class Nanoshield_LoadCell

A LoadCell Nanoshield or similar module using the ADS1230 IC.

Public Functions

Nanoshield_LoadCell(float capacity, float sensitivity, int cs = 8, bool hiGain = true, int numSamples = LOADCELL_MAX_SAMPLES)

Constructor.

Creates an object to access one LoadCell Nanoshield. The constructor parameters must match the hardware configuration used.

See

begin()

Parameters

• capacity: load cell capacity. Any measurement unit can be used.
• sensitivity: load cell sensitivity, in mV/V.
• cs: chip select pin matching the jumper selected on the board (D4, D7, etc.).
• hiGain: true if operating in high gain mode (GAIN jumper closed), false if in low gain mode (GAIN jumper open).
• numSamples: number of samples used in moving average filter. Minimum is one (no filtering) and maximum is LOADCELL_MAX_SAMPLES.

void begin(bool calibrate = true)

Initializes the module.

Initializes SPI, CS pin, Timer 2 interrupts and moving average circular buffer. Performs initial self-calibration if requested via the calibrate parameter.

Parameters

• calibrate: if true, performs ADS1230 offset calibration during initialization.

bool updated()

Checks if a new load cell reading is available.

Return

true if a new load cell reading is available.

int32_t getValue()

Gets the current 20-bit value, filtered and offset-corrected.

Return

current load cell value.

int32_t getRawValue()

Gets the current 20-bit value, filtered but not offset-corrected.

Return

current load cell value without offset correction.

int32_t getLatestValue()

Gets the latest reading (unfiltered 20-bit value), offset-corrected.

Return

latest load cell value.

int32_t getLatestRawValue()

Gets the latest reading (unfiltered 20-bit value), offset-corrected.

Return

latest load cell value, without offset correction.

float getWeight()

Gets the weight, filtered and offset-corrected.

Return

current weight reading.

void setZero()

Sets the current value to be the zero-weight value (offset or tare).

void calibrate()

Performs ADS1230 offset calibration.

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