topic Re: GT16A I2C interface with MAX1069 in 8-bit Microcontrollers

GT16A I2C interface with MAX1069

woohoo — Tue, 16 Apr 2013 16:45:01 GMT

Hi,

I am trying to use the I2C interface for the first time and am unsure of my code. I am using the GT16A as a master and am attempting to read data from the MAX1069 14 bit ADC IC. Below is my I2C initialising function and the read function. I am not getting the results I expected and I am unsure why. Any help will be greatly appreciated! edit->Turns out I forgot the pull-up resistors, but I still can't get the ADC to function correctly..

   int receiveIIC (void) // Thermistor ADC - MAX1069    {     byte dataADC[2] ;     int result;     unsigned char MAX_delay = 100;     unsigned int count;          IICC_IICEN = 1; // IIC enabled     IICC_TX = 1; // Set Transmit     IICC_MST = 1; // Set START          // Send address. LSB decides on R or W     while(IICS_TCF == 0);     IICD = 0x61;  // Address -> 0110000, LSB for receive -> 1 = 0x61          // Address -> 0110000, LSB for receive -> 0 = 0x60    for (count=0;count<MAX_delay;count++) asm("nop");           while(IICS_TCF == 0);     IICC_TX = 0;          dataADC[0] = IICD; // Receive first byte      for (count=0; count<MAX_delay;count++) asm("nop");     while(IICS_TCF == 0);          IICC_TXAK = 1;  // Send No Acknowledge     dataADC[1] = IICD; // receive second byte     for (count=0; count<MAX_delay;count++) asm("nop");     while(IICS_TCF == 0);          IICC = 0x80;              result = dataADC[0] << 8;          result += dataADC[1];                            return result;     }

Re: GT16A I2C interface with MAX1069

woohoo — Wed, 17 Apr 2013 10:19:03 GMT

So I started to attempt to write the I2C send routine that will communicate with a 14 bit, AD5647R DAC. I have encountered a problem where the high bit for the data is missing the front 2 zeroes after I split the incoming value. I have done this as shown below. Any ideas? Also still haven't managed to get the read function to work... edit->It is working with the code below now

void sendIIC (int output)
{
  byte dataDAC[2];
  unsigned char MAX_delay = 100;
  unsigned int count;

  dataDAC[0] = (output>>8) & 0x00FF; // High
  dataDAC[1] = (output) & 0x00FF; // Low

  IICC_IICEN = 1; // IIC enabled
  IICC_TX = 1; // Set Transmit
  IICC_MST = 1; // Set START

  // Send address. LSB decides on R or W
  while(IICS_TCF == 0);
  IICD = 0x1E; // Address -> 0001111, LSB for receive -> 0
  for (count=0; count<MAX_delay;count++) asm("nop");

  // Send Command byte
  while(IICS_TCF == 0);
  IICD = 0x1F; // Command: R->0 ,S->0 ,Command->011 (Write to and update DAC n) ,DAC Address->111 (Both DACs)
  for (count=0; count<MAX_delay;count++) asm("nop");

  // Send high data byte
  while(IICS_TCF == 0);
  IICD = dataDAC[0]; // Send the high bits
  for (count=0; count<MAX_delay;count++) asm("nop");

  // Send low data byte
  while(IICS_TCF == 0);
  IICD = dataDAC[1]; // Send the low bits
  for (count=0; count<MAX_delay;count++) asm("nop");

  IICC = 0x80;
}

Re: GT16A I2C interface with MAX1069

weapon — Fri, 24 May 2013 07:48:44 GMT

Hi Hobson,

There is a AN to show you how to use IIC in hcs08, hope it is useful.

http://cache.freescale.com/files/microcontrollers/doc/app_note/AN3291.pdf

And just take a look at your code, I think there are three problems.

1. You didn't check ACK from slave.

2. There are some problems after transimiting slave address

// Send address. LSB decides on R or W
while(IICS_TCF == 0);
IICD = 0x61;
// Address -> 0110000, LSB for receive -> 1 = 0x61
// Address -> 0110000, LSB for receive -> 0 = 0x60
for (count=0;count<MAX_delay;count++) asm("nop");
while(IICS_TCF == 0); // waiting the slave address sending out
while(IICS_RXAK == 1); // wait ack
IICC_TX = 0;
(void)IICD; // dummy read to clear TCF flag; this step is important,becuase TCF was set after the slave address was sent.
while(IICS_TCF == 0); // then wait for the first byte coming
dataADC[0] = IICD;

3. result = dataADC[0] << 8; I don't think that is a good practice to shift like that. dataADC[0] is a 8-bit data, your practice is depending on compiler's implicit cast. the good practice is to do cast by ourselves. like that:

result = (int)dataADC[0] << 8;

Hope my answers is helpful.

Re: GT16A I2C interface with MAX1069

weapon — Fri, 24 May 2013 07:59:07 GMT

Hi Hobson,

The send function's problem is just like receving function. you didn't wait slave's ACK. and at the last, you'd better polling IICS_TCF to confirm dataDAC[1]'s transfer is completed.

IICD = dataDAC[1]; // Send the low bits

for (count=0; count<MAX_delay;count++) asm("nop");

while(IICS_TCF == 0);

IICC = 0x80;

Re: GT16A I2C interface with MAX1069

Monica — Wed, 12 Jun 2013 23:57:06 GMT

Hello Oliver!

How is the project going?

We'd like to know if this suggestion was helpful throughout your problem, would you share with us?

Best regards,

Monica.