SPI between MSP430/432 and MCP3911 always got 0'S or 1's

[Sunnyback]

Hi,

I am trying to read ADC channel values from MCP3911 using MSP launchpad using SPI protocol. When i used Arduino Mega the protocol is working fine. But when i use any TI devices i am having a problem, it always gives me all 0'S or 1's.

I am using energia for MSP devices. Any i have chosen the appropriate pins as defined in the enegia pin layout.

msp430-----

static const uint8_t SS = 8; /* P2.7 */

static const uint8_t SCK = 7; /* P3.2 */

static const uint8_t MOSI = 15; /* P3.0 */

static const uint8_t MISO = 14; /* P3.1 */


Can someone help me troubleshoot where i am going wrong?

// SPI Stuff here
#include "SPI.h"
const uint8_t MCP3911_CS = SS; // Teensy SPI CS1 = MCP3911


void setup() {

  //SPI Bus setup
  digitalWrite(MCP3911_CS,HIGH); //
  pinMode (MCP3911_CS, OUTPUT); // MCP3911

 
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode(SPI_MODE0);
  SPI.setClockDivider(SPI_CLOCK_DIV8); //i.e. 6MHz on a Teensy running at 48MHz.
  SPI.begin();

  //Setup Serial Comms
  Serial.begin(115200);
  Write_MCP3911_Register (0x0D, B11000010);
}

int32_t adc;
void loop()
{
  //adc = Read_MCP3911_24bit(0x00);
  Read_MCP3911_Register(0x0D);
//  Serial.print("Ch0 :  ");
//  Serial.println(adc);
  delay(200);
}

uint8_t Write_MCP3911_Register (uint8_t MCP3911_Register_Address, uint8_t Command) {
  Serial.print("Command Register Received: ");
  Serial.print(MCP3911_Register_Address,HEX);
  Serial.print(" - Command Received: ");
  Serial.println(Command,BIN);

  MCP3911_Register_Address <<= 1;   //left shift address one digit
  MCP3911_Register_Address &= B00111110; // and ensure last digit is a zero for write command
  digitalWrite(MCP3911_CS, LOW); // now take CS low to enable SPI device
  SPI.transfer(MCP3911_Register_Address); // send address with write command to MCP3911
  SPI.transfer(Command); //now send payload
  digitalWrite(MCP3911_CS, HIGH); // deselect the CS pin.

  Serial.print(" Write Command Byte Sent: ");
  Serial.println(MCP3911_Register_Address,BIN); // verify what command was sent (i.e. address and write bit = 0)

  //Now Verify all went well. If so, have the function return value of one,
  //otherwise, alert the user that something is amiss.
  uint8_t Response = Read_MCP3911_Register (MCP3911_Register_Address>>1);
  if (Response == Command)  return 1;
  else
  {
    Serial.println("");
    Serial.print("Error for register: ");
    Serial.print(MCP3911_Register_Address>>1,BIN);
    Serial.print(" - Command Sent: ");
    Serial.print(Command,BIN);
    Serial.print(" - Response Received: ");
    Serial.println(Response,BIN);
    Serial.println("");
    return 0;
  }
}

uint8_t Read_MCP3911_Register (uint8_t MCP3911_Register_Address) {
 
  MCP3911_Register_Address <<=1; //left shift address one bit for command byte
  MCP3911_Register_Address |=1; // Ensure read bit is set
 
  Serial.print("  Read Byte Command Sent: ");
  Serial.print(MCP3911_Register_Address,BIN);
 
  digitalWrite(MCP3911_CS, LOW);
  SPI.transfer(MCP3911_Register_Address); // send address with read command to MCP3911
  uint8_t Response = SPI.transfer(0x00);
  digitalWrite(MCP3911_CS, HIGH);
 
  Serial.print(" - Response Received: ");
  Serial.println(Response,BIN);
  return Response;
}

void Reset_ADC()
{
 // Puts ADC into Reset Mode, i.e. stops ADC conversions until setup is complete.
  Write_MCP3911_Register (0x0D, B11000010);
}

int32_t Read_MCP3911_24bit( uint8_t MCP3911_Register_Address)
  {
    uint8_t HB,MB,LB=0, MCP3911_CTRL=0;;
    int32_t adc0code=0;
    MCP3911_CTRL = 0;
    MCP3911_CTRL =(MCP3911_Register_Address<<1); //left shift address one digit for write command
    MCP3911_CTRL |= 1; //Turn on Read Operation by toggling last bit on
    
    digitalWrite(MCP3911_CS, LOW);
    SPI.transfer(MCP3911_CTRL); // send command byte to MCP3911
    HB = SPI.transfer(0x0);//receive High Byte
    MB = SPI.transfer(0x0);//receive Middle Byte
    LB = SPI.transfer(0x0);//receive Low Byte
    digitalWrite(MCP3911_CS, HIGH);
    
    adc0code = HB;
    adc0code = adc0code<<8;
    adc0code |= MB;
    adc0code = adc0code<<8;
    adc0code |= LB;         //connecting the 3 bytes to one number
    
    
    return adc0code;// returning result
  }

Will there be anyother connections running between MSP and MCP other than SS, SCK, MOSI, MISO?
Where to connect GND? and is it required for the SPI?

Oscilloscope shows the MOSI line from MSP is outputting data as expected. Also will pullup, pulldown states of pins matter?

If u have a moment, it would be great if you can try the code I posted above and see if ur having any issues on your setup.

Buy the way, I am using MSP430FF5529 launchpad, energia 17..

Thanks in advance.

 

[kellys_eye]

A common ground between the devices is required.

Have you checked for logic level compatibility?

 

[Sunnyback]

Hi kellys_eye, thanks for your reply.
Sorry for my late response, i don't think it is the logic level causes trouble, in fact there is another micro controller on the board that is connected to the MCP3911 (only hoping using this to develop the model), so i am thinking if it will fight the MSP430 for control over SPI and lead to unexpected results...We'll get rid of it and develop our on Analog front end. Will check and see if i can read the values now. Will post if i see any trouble doing so. I just read the control register and its outputting the setting i write.