Interfacing Arduino MKR1000 with TDC1000 using SPI

Projects Networking, Protocols, and Devices
1

Hi,

I'm creating an ultrasonic flow-meter using the TDC1000, TDC7200, and Arduino MKR1000. Since this is my first time working with SPI, I thought I'd start by just reading and writing to and from CONFIG_0 on the TDC1000.

The arduino only reads zeros.
I've tried all the arduino's different SPI modes (0-3).

After a couple weeks I can't figure out what I'm doing wrong. I would greatly appreciate help in troubleshooting the below code.

Thanks.

#include <SPI.h>

int selectTDC1000 = 5;
int selectTDC7200 = 0;

int enableTDC1000 = 7;
int enableTDC7200 = 1;

int dataReadyPin = 4;
int channelSelect = 3;

byte CONFIG1_address = 0x00;
byte CONFIG1_instruction = 0x00;
unsigned int whatWasRead = 0x00;

unsigned int readRegister(int device, byte address, int bytesToRead);
void writeRegister(int device, byte address, byte data);

void setup()
{
  Serial.begin(9600);
  SPI.beginTransaction(SPISettings(16000000, MSBFIRST, SPI_MODE0));

  pinMode(selectTDC1000, OUTPUT);
  pinMode(selectTDC7200, OUTPUT);

  pinMode(enableTDC1000, OUTPUT);
  pinMode(enableTDC7200, OUTPUT);

  pinMode(dataReadyPin, INPUT);
  pinMode(channelSelect, OUTPUT);

  digitalWrite(selectTDC1000, HIGH);//active low
  digitalWrite(selectTDC7200, HIGH);//active low

  digitalWrite(enableTDC1000, LOW);
  digitalWrite(enableTDC7200, LOW);
  
}

void loop()
{  
  digitalWrite(enableTDC1000, HIGH);
  delayMicroseconds(350);
  
  //***Read and print register***********************************  
  whatWasRead = readRegister(1000, CONFIG1_address, 1);

  Serial.print("Before write: ");
  Serial.println(whatWasRead, BIN);
  //*************************************************************
  
  //***Write new byte to register, read byte from register*******
  writeRegister(1000, CONFIG1_address, 0x02);
    
  whatWasRead = readRegister(1000, CONFIG1_address, 1);
  
  Serial.print("After write: ");
  Serial.println(whatWasRead, BIN);
  Serial.print("\n");
  //*************************************************************
  
  digitalWrite(enableTDC1000, LOW);
  
}

void writeRegister(int device, byte address, byte data)
{

  if(device == 1000)
  {
    digitalWrite(selectTDC1000, LOW);//low active
  }
  else if(device == 7200)
  {
    digitalWrite(selectTDC7200, LOW);//low active
  }
  
  address |= 1000000;
  
  SPI.transfer(address);
  SPI.transfer(data);

  if(device == 1000)
  {
    digitalWrite(selectTDC1000, HIGH);//low active
  }
  else if(device == 7200)
  {
    digitalWrite(selectTDC7200, HIGH);//low active
  }
  
}

unsigned int readRegister(int device, byte address, int bytesToRead)
/* device: 1000 or 7200.
 * address: register address on specified device.
 * how many bytes long is the data we're reading?
 */
{

  byte inByte = 0;           // incoming byte from the SPI
  unsigned int result = 0;   // result to return
  Serial.print("Address we're reading from: ");
  Serial.print(address, BIN);
  Serial.print("\n");

  if(device == 1000)
  {
    digitalWrite(selectTDC1000, LOW);//low active
  }
  else if(device == 7200)
  {
    digitalWrite(selectTDC7200, LOW);//low active
  }
  
  byte readFromThisRegister = address;//read bit comes before address (MSBF) so 0b000000 = 0b0000000

  SPI.transfer(readFromThisRegister);
  result = SPI.transfer(0x00);

  bytesToRead --;
  
  while(bytesToRead > 0)
  {

    result = result << 8;
    inByte = SPI.transfer(0x00);    
    result = result | inByte;
    bytesToRead --;
    
  }

  if(device == 1000)
  {
    digitalWrite(selectTDC1000, HIGH);//low active
  }
  else if(device == 7200)
  {
    digitalWrite(selectTDC7200, HIGH);//low active
  }
  
  return result; 
}
2

I've tried all the arduino's different SPI modes (0-3).

According to the datasheet the device is expecting SPI mode 3.

SPI.beginTransaction(SPISettings(16000000, MSBFIRST, SPI_MODE0));

Does your application really need the highest possible frequency the chip supports?
At 16MHz the length of the SPI connections must be very short and well shielded, so a breadboard setup probably won't work. BTW I'm missing a wiring diagram. How did you connect the Arduino to the chip?

The SPI.beginTransaction() call should be in the register read/write routines and in the setup() there should be an SPI.begin() call.

3

Thanks, pylon.

I've attached the wiring diagram.

wiring-diagram.png

4

Thanks, pylon.

I've made the changes you've suggested (see below), but I'm still just reading 0's.

I also simplified the code to just read and not write.

:frowning: :frowning: :frowning:

#include <SPI.h>

int selectTDC1000 = 5;
int selectTDC7200 = 0;

int enableTDC1000 = 7;
int enableTDC7200 = 1;

int dataReadyPin = 4;
int channelSelect = 3;

byte CONFIG_0_address = 0x00;
unsigned int whatWasRead = 0x00;

unsigned int readRegister(int device, byte address, int bytesToRead);
void writeRegister(int device, byte address, byte data);

void setup()
{
  Serial.begin(9600);
  SPI.begin();

  pinMode(selectTDC1000, OUTPUT);
  pinMode(selectTDC7200, OUTPUT);

  pinMode(enableTDC1000, OUTPUT);
  pinMode(enableTDC7200, OUTPUT);

  pinMode(dataReadyPin, INPUT);
  pinMode(channelSelect, OUTPUT);

  digitalWrite(selectTDC1000, HIGH);//active low
  digitalWrite(selectTDC7200, HIGH);//active low

  digitalWrite(enableTDC1000, HIGH);
  digitalWrite(enableTDC7200, LOW);
  
}

void loop()
{  
  delayMicroseconds(350);
  
  //***Read and print register***********************************  
  whatWasRead = readRegister(1000, CONFIG_0_address, 1);

  Serial.print("CONFIG_0: ");
  Serial.println(whatWasRead, BIN);
  //*************************************************************
  
}

unsigned int readRegister(int device, byte address, int bytesToRead)
/* device: 1000 or 7200.
 * address: register address on specified device.
 * how many bytes long is the data we're reading?
 */
{

  byte inByte = 0;           // incoming byte from the SPI
  uint32_t result = 0;   // result to return
  SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE3));

  if(device == 1000)
  {
    digitalWrite(selectTDC1000, LOW);//low active
  }
  else if(device == 7200)
  {
    digitalWrite(selectTDC7200, LOW);//low active
  }

  SPI.transfer(address);
  result = SPI.transfer(address);

  bytesToRead --;
  
  while(bytesToRead > 0)
  {

    result = result << 8;
    inByte = SPI.transfer(0x00);    
    result = result | inByte;
    bytesToRead --;
    
  }

  if(device == 1000)
  {
    digitalWrite(selectTDC1000, HIGH);//low active
  }
  else if(device == 7200)
  {
    digitalWrite(selectTDC7200, HIGH);//low active
  }
  SPI.endTransaction();
  delayMicroseconds(50);
  
  return result; 
}
5

I currently don't find any error in your code. In the wiring I would remove the connection from CLKIN to pin 9 (not necessary) and connect RESET to GND (to not let it floating).

If that doesn't help I would check with a logic analyzer.

6

Thanks, pylon.
Well, I can read and write from the TDC7200 now, but not the TDC1000, which is weird as the chips are similar and made to work together. :frowning:

7

Are you sure your TDC1000 is working correctly?

8

I've tried it with two different TDC1000s, so the fault is probably mine.

9

Hello, NikBruce

Your code is helpful to me. Have you completed this project? I have some problems that cannot be solved.