I2C Interface on LPCXpresso860

[Prasanth91]

Hello,  

I just started at NXP. I picked the LPCXpresso860-MAX as my Evaluation Board and I'm learning how to develop applications with it. Right now, I'm working on connecting the LPC860-MAX microcontroller to the SHT-31 humidity and temperature sensor using I2C.

I attempted as shown below.

Hardware Setup:

LPC860-MAX connections:

SCL (P0_10)

SDA (P0_11)

SHT-31 connections:

VCC → 3.3V 

GND → Ground

SCL → LPC860-MAX SCL

SDA → LPC860-MAX SDA

Software Setup: 

/*

 * Program for SHT-31 (Temperature & Humidity sensor)

 */

#include <stdio.h>

#include "pin_mux.h"

#include "board.h"

#include "fsl_debug_console.h"

#include "i2c.h"

#include "wait.h"

#define SHT31_ADDR    0x44  // SHT-31 I2C address

enum registers {

Temp,

Conf,

T_LOW, 

T_HIGH

};

void mcu_init( void );

// Function to send command to SHT-31

void SHT31_SendCommand(uint8_t commandHigh, uint8_t commandLow) {

    uint8_t data[2];

    data[0] = commandHigh;

    data[1] = commandLow;

    // Send command to SHT-31 over I2C

    i2c_reg_w16( SHT31_ADDR, Temp, data );

}

// Function to read data from SHT-31

void SHT31_ReadData(uint8_t *buffer, uint8_t length) {

    // Read 6 bytes from SHT-31 (Temperature + Humidity)

    i2c_reg_r16( SHT31_ADDR, buffer );

}

int main( void )

{

mcu_init();

i2c_init( 100 * 1000 ); // setting I2C clock frequency in "Hz"

    uint8_t data[6];

    int16_t rawTemperature, rawHumidity;

    float temperature, humidity;

    // Send command to read temperature and humidity

    SHT31_SendCommand(0x2C, 0x06); // Command for temperature & humidity

PRINTF( "\r\nLPC860-MAX with SHT-31\r\n\r\n" );

    while ( 1 )

    {

        // Read the response (6 bytes)

        SHT31_ReadData(data, 6);

        // Calculate temperature from raw data

        rawTemperature = (data[0] << | data[1];

        temperature = -45 + (175 * rawTemperature / 65535.0);

        // Calculate humidity from raw data

        rawHumidity = (data[3] << | data[4];

        humidity = 100 * rawHumidity / 65535.0;

        // Output the results (for example, via UART or LED)

        printf("Temperature: %.2f °C\n", temperature);

        printf("Humidity: %.2f Percentage\n", humidity);

        wait_ms( 1000 );

    }

    return 0;

}

void mcu_init( void )

{

CLOCK_Select( BOARD_DEBUG_USART_CLK_ATTACH );

CLOCK_Select( kI2C0_Clk_From_MainClk );

BOARD_InitBootPins();

BOARD_BootClockFRO60M();

BOARD_InitDebugConsole();

if ( SysTick_Config( SystemCoreClock / 1000U ) )

{

PRINTF( "Fail: SysTick_Config()\r\n" );

while ( 1 );

}

}

status_t i2c_reg_w16( const uint8_t addr, const uint8_t reg, const uint16_t data )

{

uint8_t b[ 3 ] = { reg, (data >> 8), data & 0xFF };

return i2c_send( addr, b, sizeof( b ), I2C_STOP );

}

uint16_t i2c_reg_r16( const uint8_t addr, const uint8_t reg )

{

uint8_t b[ 2 ] = { reg, 0 };

i2c_send( addr, b, 1, I2C_REPEATED_START );

i2c_receive( addr, b, 2 );

return (b[ 0 ] << | b[ 1 ];

}

I received the following output:

Humidity: 0.20 Percentage

Temperature: 11.23 °C

Humidity: 0.20 Percentage

Temperature: 11.23 °C

Humidity: 0.20 Percentage

Temperature: 11.23 °C

Humidity: 0.20 Percentage

It looks like the value isn't being read correctly. Could you please help fix this by sharing a sample code that can be used for development?

[Pavel_Hernandez]

Hello, I recommend download the last IDE MCUXpresso on the next link.

MCUXpresso IDE for NXP MCUs | Linux, Windows and MacOS | NXP Semiconductors | NXP Semiconductors

On the next link you could find the SDK and the examples.

Select Board | MCUXpresso SDK Builder

Best regards,
Pavel