MSP430G2553: To MSP430G2553 I2C link

brian elliott said:

Ran program to return addresses of connected devices - all addresses from 0 to 127 were returned in a loop - How does MSP recognise itself as a Slave device ?  Or are there other issues ?

>

To answer your first question, the slave recognizes itself as a slave device when the UCMST bit is 0. It should automatically be configured properly if you've flashed the slave with the correct firmware.

The code below works on ARDUINO UNO / NANO combination.

[ On advice from 430h Forum I used ' revised ' twi.c and twi.sw.c files as supplied ( via e2e link : from ROBERT WESSELS TI EMPLOYEE )

LINK :-

http://e2e.ti.com/support/development_tools/code_composer_studio/f/81/p/529036/1924562#1924562

Below were obtained from Youtube video :- ]

MASTER :-

#include <Wire.h>
#define LED RED_LED
void setup()
{
Wire.begin(); // join i2c bus (address optional for master)
delay(2000);
pinMode(LED, OUTPUT);
}



void loop()
{
Wire.beginTransmission(4); // transmit to device #4

Wire.write('H'); // sends one byte
Wire.endTransmission(); // stop transmitting
delay(3000);
digitalWrite(LED, HIGH);


delay(1000);
Wire.beginTransmission(4); // transmit to device #4

Wire.write('L'); // sends one byte
Wire.endTransmission(); // stop transmitting
delay(3000);
digitalWrite(LED, LOW);
delay(1000);
}

SLAVE :-

#include <Wire.h>
#define LED RED_LED
void setup()
{
Wire.begin(4); // join i2c bus with address #4
Wire.onReceive(receiveEvent); // register event
// Serial.begin(9600); // start serial for output
}

void loop()
{
// delay(100);
}

// function that executes whenever data is received from master
// this function is registered as an event, see setup()
void receiveEvent(int howMany)

{
// delay(100);
digitalWrite(LED,HIGH);
delay(1000);
digitalWrite(LED,LOW);
delay(1000);

while(Wire.available()) // loop
{
char c = Wire.read(); // receive byte as a character
Serial.print(c); // print the character
if( c =='H')
{
digitalWrite(LED,HIGH);
delay(1000);
}
else if ( c =='L')
{
digitalWrite(LED,LOW);
delay(1000);

}
}
}

I also ran this :-

#include <Wire.h>

void setup()
{
  Serial.begin(9600);
  Serial.println("Start!");
  
  Wire.setModule(0);
  Wire.begin();
}

void loop()
{
  findAddress();
  delay(1000);
}

uint8_t fromAddress = 0;
uint8_t toAddress = 127;

void findAddress()
{
  for (uint8_t a = fromAddress; a < toAddress; a++)
  {
    Wire.beginTransmission(a);
    int endStatus = Wire.endTransmission();

    if (endStatus == 0)
    {
      Serial.print("Found device at: 0x");
      Serial.println(a, HEX);
    }
  }
}

This produced a loop of all addresses from 0 to 127.

Note Wire.setModule (0) crashes program !

Any suggestions - are delays too large for MSP430 ?

Regards

B. Elliott

PS Pull-ups are 4k7 , common ground used. Green LED link removed.

While the following app note is older, it still has some good discussion about something similar to what you're wanting to do.

Using the USCI I2C Slave

Also, as Caleb mentioned in one of your other threads, we offer many code examples in MSP430Ware for I2C (they're named 'msp430g2xx3_uscib0_i2c_xx.c'). Recently, he has written an excellent app note that may also help you now and in the future.

Solutions to Common eUSCI and USCI Serial Communication Issues on MSP430™ MCUs

Regards,

James

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