FDC1004EVM: MSP432 + FDC1004 over I2C; Having trouble establishing connection

Dan,

A couple of preliminary items to confirm before we take a deeper dive into your problem:

1. The FDC1004 EVM schematic shows ~5k resistors on the SDA and SCL lines.
Its hard to imagine the value differences could be the problem, but please change your board's values to 4.99k to see if it helps.

2. The data sheet gives the following:

8.5.1 Serial Bus Address
To communicate with the FDC1004, the master must first address slave devices via a slave address byte. The slave address byte consists of seven address bits and a direction bit that indicates the intent to execute a read or write operation. The seven bit address for the FDC1004 is (MSB first): b101 0000.

Are your  protocols following this?

Regards,
John

Hi John,

1) I happen to have 4.7k resistors on the right now, will these suffice? Don't think I have the exact value (4.99k).

2) I open the I2C connection with Wire.begin() and then every time I wish to communicate I do Wire.beginTransmission(0x50). This is the address from that data sheet. I wanted to be sure, so I ran the code below (simple I2C scanner) but it doesn't find the 1004 at any address. However, when I run the scanner on an Arduino Uno, it will (if I hold the wires in the breadboard juuust right). This makes me think I have something wrong wired up? But I cannot for the life find where it might be.

#include <Wire.h>

void setup() {
  Wire.begin();

  Serial.begin(9600);
  while (!Serial); // Leonardo: wait for serial monitor
  Serial.println("\nI2C Scanner");

}

void loop() {
  int nDevices = 0;

  Serial.println("Scanning...");

  for (byte address = 1; address < 127; ++address) {
    // The i2c_scanner uses the return value of
    // the Write.endTransmisstion to see if
    // a device did acknowledge to the address.
    Wire.beginTransmission(address);
    byte error = Wire.endTransmission();

    if (error == 0) {
      Serial.print("I2C device found at address 0x");
      if (address < 16) {
        Serial.print("0");
      }
      Serial.print(address, HEX);
      Serial.println("  !");

      ++nDevices;
    } 
    else{
      Serial.print("Error ");
      Serial.print(error);
      Serial.print(" at address 0x");
      if (address < 16) {
        Serial.print("0");
      }
      Serial.println(address, HEX);
    }
  }
  if (nDevices == 0) {
    Serial.println("No I2C devices found\n");
  } else {
    Serial.println("done\n");
  }
  delay(2000); // Wait 5 seconds for next scan

}

I also put LED's in place on the SCL and SDA lines to see when there is data being passed. When connected to the Arduino they seem to flash properly to indicate data is being transmitted, however they are always off when connected to the MSP432.

Dan,

Can your MSP432 to communicate with some other board via the I2C?

Hi John,

I used the arduino board to test this.

The arduino acting as a master can find the 432 as a slave. BUT the 432 acting as a master cannot find the arduino as a slave.

Dan,

After conferring with my colleagues, this sounds like an issue with the MSP432.

I will transfer this thread to that E2E forum so the experts can help get it resolved.

Thank you for your patience.

Hello, thank you for the help! I will keep checking back and try to get some more work over the weekend. Hopefully I can get something new to work.