next topic »

[on:]

Could please help me. I am using the Arduino UNO and a Maxim MAX9611, the communication is i2C with the Wire.h I am confused where to start. I understand I2c but need getting communication correct between UNO & MAX9611. How to I start talking to the MAX9611 and reading the information? The datasheet is at the following website http://datasheets.maximintegrated.com/en/ds/MAX9611-MAX9612.pdf

[Reply #1 on:]

http://www.gammon.com.au/i2c

[Reply #2 on:]

I do understand i2c, but my difficulty is the structure talking to the MAX9611

[Reply #3 on:]

Have you tried anything? What is "my difficulty" exactly?

What have you tried?

I would expect at this stage to see a bit of code where you initialize I2C, try to communicate with the device at the documented address, try to read a register, that sort of thing.

[Reply #4 on:]

I have tried. Following is my program: (My result is "Temp is 31.14" on the LCD, which is incorrect and does not track the temperature)

Code:

#include <TimerOne.h>
/*
 Analog pins 4 (SDA),5(SCL)
 */
#include <Wire.h>
#include <Adafruit_MCP23017.h>
#include <Adafruit_RGBLCDShield.h>
// The LCD and DS3132 use the I2C SCL on analog pin 5 and SDA on analog pin 4.
Adafruit_RGBLCDShield lcd = Adafruit_RGBLCDShield();

int temp_MSB;
int temp_LSB;
double tempresolution = 0.48;

void setup()
{
  lcd.begin(16, 2);
  Serial.begin(9600);
  Wire.begin();
}

void loop()
{
  int i, sign, temp1; //added sign and temp1. JZ 05/21/2012
  double temperature;
  lcd.setCursor(0,1);
  while (1) {
    Wire.write(0xE0);
    Wire.write (0x08);
    Wire.requestFrom(0xE1, 1);
    temp_MSB = Wire.read();

    Wire.write(0xE0);
    Wire.write (0x09);
    Wire.requestFrom(0xE1, 1);
    temp_LSB = Wire.read();

    // changed for MAX9611 internal temperature output (9 bits with sign). JZ 05/21/2012
    sign = (temp_MSB>>8 & 0x1); //extract sign bit
    temp1 = (((temp_MSB<<1) & 0xFE)|((temp_LSB>>8)&0x1)); //extract internal temperature ADC steps
    if(sign)
    {
      temperature = (-1)*((~temp1 & 0xFF) + 1)*tempresolution; //sign bit=1, temperature is negative (two's compliment)
    }
    else
    {
      temperature = temp1 * tempresolution; //otherwise, the temperature is a positive number
    }
    temperature = ((temperature * 1.8) + 32); //convert to degree F

  lcd.setCursor(0,1);
  lcd.print("Temp is ");
  if (sign==0)
  {
    lcd.print("-");
  }
  lcd.print(temperature);
  }

}

[Reply #5 on:]

Oh, right! You have code. It was a secret, though.

Read this before posting a programming question


Please edit your post, select the code, and put it between [code] ... [/code] tags.

You can do that by hitting the # button above the posting area.

[Reply #6 on:]

You would have got a much faster response if you had read the sticky, and posted your code, in the first place. A day has been gone because you didn't.

[Reply #7 on:]

My apologies, I made a mistake.  Can someone help?

[Reply #8 on:]

Code:

  while (1) {
    Wire.write(0xE0);
    Wire.write (0x08);
    Wire.requestFrom(0xE1, 1);
    temp_MSB = Wire.read();

    Wire.write(0xE0);
    Wire.write (0x09);
    Wire.requestFrom(0xE1, 1);
    temp_LSB = Wire.read();

I do understand i2c,  ...

OK, now go read my page, which you obviously haven't so far:

http://www.gammon.com.au/i2c

Things that jump out at me:

• You need Wire.beginTransmission
• You need Wire.endTransmission
• I2C device addresses go up to 119 (x77) but you are using 0xE1

[Reply #9 on:]

I am reading your I2c instructions. I have changed my program to include:
    Wire.beginTransmission(0xE0);
    Wire.write(0x08);
    Wire.endTransmission(); // This function sets the pointer to the registerLocation from where we want to read the data
    Wire.requestFrom(0xE1,1);
    temp_MSB = Wire.read();

Also the address of the MAX9611 starts at 0xE0 thru 0xEF

[Reply #10 on:]

Also the address of the MAX9611 starts at 0xE0 thru 0xEF

The library shifts the address left one and adds in the read/write bit. You want to use 0x70 (half of 0xE0) and leave that part to the library. In other words use 0x70 for both reading and writing.

[Reply #11 on:]

Run this scanner to prove that point, and to check your wiring is correct:

http://www.gammon.com.au/forum/?id=10896&reply=6#reply6

[Reply #12 on:]

That worked, and yes something showed up on 70, although it still does not function correctly. I will work on it further and get back to you. Thank you for all your help

[Reply #13 on:]

Thanks for your help. Following is my code and so far it is working. Next I will add power supply and load.

Code:

#include <TimerOne.h>
/*
 Analog pins 4 (SDA),5(SCL)
 */
#include <Wire.h>
#include <Adafruit_MCP23017.h>
#include <Adafruit_RGBLCDShield.h>
// The LCD and DS3132 use the I2C SCL on analog pin 5 and SDA on analog pin 4.
Adafruit_RGBLCDShield lcd = Adafruit_RGBLCDShield();

int temp_MSB;
int temp_LSB;
double tempresolution = 0.50;

void setup()
{
  lcd.begin(16, 2);
  Serial.begin(9600);
  Wire.begin();
}

void loop()
{
  int i, sign, temp1; //added sign and temp1. JZ 05/21/2012
  double temperature;
  lcd.setCursor(0,1);
  while (1) {
    Wire.beginTransmission(0x70);
    Wire.write(0x08);
    Wire.endTransmission();

    Wire.requestFrom(0x70,2);
    temp_MSB = Wire.read();
    temp_LSB = Wire.read();
 
    // changed for MAX9611 internal temperature output (9 bits with sign). JZ 05/21/2012
    sign = (temp_MSB>>8 & 0x1); //extract sign bit
    temp1 = (((temp_MSB<<1) & 0xFE)|((temp_LSB>>8)&0x1)); //extract internal temperature ADC steps
    if(sign)
    {
      temperature = (-1)*((~temp1 & 0xFF) + 1)*tempresolution; //sign bit=1, temperature is negative (two's compliment)
    }
    else
    {
      temperature = temp1 * tempresolution; //otherwise, the temperature is a positive number
    }
    temperature = ((temperature * 1.8) + 32); //convert to degree F

  lcd.setCursor(0,0);
  lcd.print("Temp is ");
  if (sign==1)
  {
    lcd.print("-");
  }
  lcd.print(temperature);
  }
}

[Reply #14 on:]

I have written a program (see following) to read the MAX9611 Data and display it on an LCD. I will be changing the program to output to a screen and also have the ability to have up to 16 different addressed MAX9611 ICS reporting.  The problem this I have is that the Arduino  used a 7 bit i2c address and assumes that the 8th bit is either a one or a zero. In the case of the MAX9611, the write and read addresses are E0/E1, E2/E3, E4/E5, E6/E7, ..... FE/FF. My question is, how do I tell the Arduino  that the write/read bit is not necessarily a one or a zero?

Code:

/*********************************************************************
 * FileName: MAX9611.h
 * Dependencies: None
 * Overview: Defines function prototypes, I2C address, global
 * variables.
 ********************************************************************/


// ***************** User-configurable parameters ********************


// main voltage range
#define voltage_max 56.3
#define main_voltage_min 1.0

// main current range
#define current_max 10000
#define current_min 0

// I2C address
#define MAX9611_address 0x70 //0x70 is the Arduino MAX9611 address actual address is 0xE0

// Sense resistor values

// *******************************************************************

// Function prototypes

double get_MAX9611_voltage(void);
double get_MAX9611_current(void);

//void init_MAX9611 ();

Code:

/*********************************************************************
 * FileName: MAX9611.cpp
 * Dependencies: MAX9611.h (include here and in main)
 * Wire.h (include here and in main)
 ********************************************************************/


/*********************************************************************
 * Function:        void get_MAX9611_voltage (void),
 * void get_MAX9611_current (void)
 * PreCondition:    None.
 * Input:            None.
 * Output:          None.
 * Side Effects:    None.
 * Overview:        Function for obtaining MAX9611 voltage via I2C
 * bus.
 *
 ********************************************************************/

#include "MAX9611.h"
#include "Wire.h"

double MAX9611_voltage;
double MAX9611_current;

double get_MAX9611_voltage (void){
int msb;
int lsb;


    Wire.beginTransmission(0x70);
    Wire.write(0x0A);
    Wire.write(0x03);
    Wire.endTransmission();
   
    Wire.beginTransmission(0x70);
    Wire.write(0x02);
    Wire.endTransmission();

    Wire.requestFrom(0x70,2);
    msb = Wire.read();
    lsb = Wire.read();
    Wire.endTransmission();

    MAX9611_voltage = ((msb)<<4)+(lsb>>4);
    MAX9611_voltage = ((MAX9611_voltage/4096)*57.3);

return MAX9611_voltage;
}

double get_MAX9611_current (void){
int msb;
int lsb;
int result;

    Wire.beginTransmission(0x70);
    Wire.write(0x0A);
    Wire.write(0x00);
    Wire.endTransmission();
   
    Wire.beginTransmission(0x70);
    Wire.write(0x00);
    Wire.endTransmission();

    Wire.requestFrom(0x70,2);
    msb = Wire.read();
    lsb = Wire.read();
    Wire.endTransmission();

    result = ((msb)<<4)+(lsb>>4);
    MAX9611_current = (((result/4096)*440)/.05);

    return MAX9611_current;
}

Code:

#include <MAX9611.h>
#include <Wire.h>
/*
 Analog pins 4 (SDA),5(SCL)
 */
#include <Adafruit_MCP23017.h>
#include <Adafruit_RGBLCDShield.h>
Adafruit_RGBLCDShield lcd = Adafruit_RGBLCDShield();

int msb;
int lsb;

void setup()
{
  lcd.begin(16, 2);
  Serial.begin(9600);
  Wire.begin();
}

void loop()
{
  double volts;
  double current;
 
  lcd.setCursor(0,1);
  while (1) {

 
  volts = get_MAX9611_voltage();
 
  lcd.setCursor(9,0);
  lcd.print(volts, 3);
  lcd.print(" V");
 
    current = get_MAX9611_current();

  lcd.setCursor(0,0);
  lcd.print(current, 3);
  lcd.print(" A");

 
  lcd.setCursor(2,1);
  lcd.print((current * volts), 6);
  lcd.print(" Watts");
  }
}