Load Cell 2 Click

How does it work?

The NAU7802 is a precision low-power 24-bit analog-to-digital converter (ADC), with an onboard low-noise programmable gain amplifier (PGA), onboard RC or Crystal oscillator, and a precision 24-bit sigma-delta (Σ-Δ) analog to digital converter (ADC). The NAU7802 device is capable of up to 23-bit ENOB (Effective Number Of Bits) performance. This device provides a complete front-end solution for bridge/sensor measurement such as in weigh scales, strain gauges, and many other high resolution, low sample rate applications.

The NAU7802 have many built-in features, which enable high performance applications with very low external parts count. Additionally, both operating current and standby current are very low, and many power management features are included. These enable powering only those elements of the chip that are needed, and also, to operate at greatly reduced power if the full 23-bit ENOB performance is not required.

The Programmable Gain Amplifier (PGA) provides selectable gains from 1 to 128. The A/D conversion is performed with a Sigma-Delta modulator and programmable FIR filter that provides a simultaneous 50Hz and 60Hz notch filter to effectively improve interference immunity. Also, this device provides a standard 2-wire interface compatible with I2C protocol for simple and straightforward connection to and interoperation with a wide range of possible host processors.

Calibration is not required for low accuracy applications, but may be needed in sensitive applications. When calibration is used the system designer has three options (details in NAU7802 datasheet).

The power supply is 3.3V and this allows only 3.3V MCUs to be interfaced with the Click boards™ directly.

Specifications

Pinout diagram

This table shows how the pinout on Load Cell 2 Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
	NC	2	RST	INT	15	RDY	Data Ready
	NC	3	CS	RX	14	NC
	NC	4	SCK	TX	13	NC
	NC	5	MISO	SCL	12	SCL	I2C Clock
	NC	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

Software Support

We provide a library for the Load Cell 2 Click on our LibStock page, as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Library Description

The library covers all the necessary functions to control Load Cell 2 click board. Library performs a standard I2C interface communication.

Key functions:

• float loadcell2_get_weight ( loadcell2_data_t *cell_data ) – Get weight function.
• uint32_t loadcell2_get_result ( void ) – Get results function.
• void loadcell2_set_default_config ( void ) – Set default sensor configuration function.

Examples description

The application is composed of three sections :

• System Initialization – Initializes I2C, set INT pin as input and stert to write log.
• Application Initialization – Initializes I2C driver and performs the device reset, set power on and default configuration. Sets tare the scale, calibrate scale and start measurements.
• Application Task – (code snippet) – This is an example which demonstrates the use of Load Cell 2 Click board. Display the measurement of scales in grams [g]. Results are being sent to the Usart Terminal where you can track their changes. All data logs write on USB uart changes for every 1 sec.

void application_task ( )
{
    weight_val = loadcell2_get_weight( &cell_data );

    log_display( weight_val );

    Delay_ms( 1000 );
}

Additional Functions :

• void log_display ( float display_val ) – Function displays readings as floating point value with two decimal places.

The full application code, and ready to use projects can be found on our LibStock page.

Other mikroE Libraries used in the example:

• I2C
• UART
• Conversions

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.