ADS1296 register configuration

Kaspars said:

while (!(IFG1 & UTXIFG0));           
  TXBUF0 = 0x41;                             // WHAT IS THIS?
 
  while (!(IFG1 & UTXIFG0));
  TXBUF0 = 0x03;                             // WHAT IS THIS?

Kaspars,

Please see page 40 of the data sheet.  TXBUF = 0x41 loads the 8-bit shift register of the transmitter.  The WREG command is 010r rrrr followed by 000n nnnn so the two transmit operations above are sending WREG starting at address 1 with the intention to modify four registers in total.  If you wanted to write to CH4SET (address eight) and only modify that register, you would WREG 0x48, 0x00, 0x(8-bit desired value).

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OK, lets try that!

1. You understand the SDATAC command correctly.
2. Yes, you understand the beginning of WREG command.  TXBUF = 0x41 tells the device you want to start writing at CONFIG1.
3. After WREG, the 0x03 defines the number of registers to be written to minus one.  Please review note(2) under Table 11 on page 40.  Sending 0x03 therefore assumes you are writing four registers, CONFIG1, CONFIG2, CONFIG3 and LOFF.
4. In the example above, CONFIG1 receives 0xE5, CONFIG2 receives 0x00, CONFIG3 receives 0xC0and LOFF receives 0x00.
5. From the sample code, the next line with 0x45 re-starts the WREG, beginning at address five, writing to the (0x07) eight channel registers.  These two lines could have been avoided if in (3) above 0x0B was written instead of 0x03.  If the intention was to skip the LOFF register, 0x02 should have been transmitted in (3).
6. Here we have a FOR LOOP which runs eight times.  Assuming (5) came just ahead of this loop, this would write 0x10 to each CHx register, the for (i=0; i<3;i++) followed by everything between the curly brackets{} makes that happen.  The //RDATAC comment does not make sense to me, you would not need to send that command 8 times.  The second FOR LOOP is simply a delay, the semicolon after for (i=0; i<3;i++); just forces the code to essentially pause.

I hope that helps clarify things for you!

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Kaspars,

Ports P3.5 and P3.6 do not match your code where you used P3.6 and P3.7.  But I think the bigger issue is in how you use CS assignment in your code.  It appears that you never actually change CS.  To set low it should be '&= CS' and to set high it should be '|= ~CS'.  You do not want to use '~' operator is every case.

Best regards,

Bob B

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Kaspars,

Lots of good pictures.  Let's work some more on troubleshooting, and we'll look at just the first scope picture for now.  The first thing is not all the plots are at the same voltage level.  So DIN and DOUT are really just noise.  What might be causing the noise?  Maybe a bad scope ground, or maybe a bad connection from the micro.  Is this a PCB layout?  Or are you using a bunch of wires to connect to the EVM?

Another thing to notice is the CS.  CS goes low for the first set of SCLKs and stays high for the remainder.  CS must always be low when trying to communicate to the device.  In other words, if you send SCLKs to the device to read or write, CS must be low.

Another thing to note is that if the first SCLK set is supposed to be a command, then DIN is not really sending any data.  The problem on my end is that I have no idea what you are trying to do at this point.  Nor do I know if START is high if you are trying to read data.  So, what does this first scope shot supposed to be showing me?

Best regards,

Bob B

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Kaspars,

The supply voltage connections you have specified is acceptable.

For the software command you are writing 0x03 to the TXBUF0 buffer.  This buffer is specified in the header file for the MSP430 device.  For the MSP430F1611, this would relate to the '0' peripheral (SIMO0-pin 30).

So for the 'while' you are waiting for anything that may still be in the TX buffer to clear before assigning something new to the buffer.  When you assign a value to the TX buffer, the value will be clocked out of the peripheral.

Best regards,

Bob B

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Kaspars,

Great job of showing your setup!  You must have cleaned up a lot of your noise issues as the scope shots appear much cleaner.  It also appears that you now have data coming out of the micro.

As far as the code is concerned, as I've mentioned before it is always difficult to follow someone else's code and interpret what is trying to be done.  It appears to me that perhaps someone is reading data and then transmitting data out the UART (perhaps to a Serial-to-USB converter that can be written/read by a PC.)  Is this what you are trying to do?  It would appear so from the PS in your previous post (at least the write to PC part.)

The variable 'rx_on' appears to be a sort of flag set by the UART communication.  The program will sit in the while loop until a character has been received by the UART.  The received character is 'rx_data' and the program will jump back to the initial while loop and set 'rx_on' back to zero unless the received character is 0xFF (Start command).  The program then reads the data and then transmits the data out the UART serial port.

My problem with this scenario is that it keeps changing the peripheral port '0' from SPI to UART modes and then back again.  I would have assigned my ports differently so that I could have used the '0' peripheral for SPI and the '1' peripheral for the UART.  Perhaps the original MSP430 used by the code author only had one peripheral.

So the reason the single step fails is 'rx_on' never goes to something other than '0' and the single step keeps trying to evaluate it and cannot execute the step.  If you don't want to use the PC to start the program, then you need to eliminate the parts of the code that deal with the UART receive.  The following code may work to start reading the data (note I commented out the lines I believe are related to receive UART start command):

while(1)                               
 {
  // while(rx_on==0);                                   // What is this? Why I need this? And what it do?
  // rx_on = 0;                                             // What is this? Why I need this? And what it do?
  // if(rx_data==0xff) goto NOSTOP;          // What is this? Why I need this? And what it do?
  // goto STOP_AD;                                    // What is this? Why I need this? And what it do?
    
// NOSTOP:
  configure_spi();                                    // Setup SPI
 
  P2OUT &= ~CS_0;                              // SET CS "low"
 
  P3OUT |= START;                                // SET START "high"
 
  while (!(IFG1 & UTXIFG0));                 // RDATAC (Read Data Continuosly)
  TXBUF0 = 0x10;
 
  while (!(IFG1 & UTXIFG0));              
  TXBUF0 = 0x00;                                 // What is this? Why I need this? And what it do? I have no idea why this is done, but it should not hurt anything as it is a NOP
  while (!(IFG1 & UTXIFG0));
 
  P2OUT |= ~CS_0;                               // SET CS "high"  conversation ends
 
  while(1)                               
  {
   P2OUT &= CS_0;                             // Set CS "low"
   while((P2IN & 0x02));                        // What is this? Why I need this? And what it do? Important This is waiting for P2.2 to go low...perhaps this port pin was assigned to DRDY at some point by the author of the code
  
   for (i = 0; i < 3; i++)                           // Read Status register // What is this?  What it do? This for loop reads three bytes of STATUS data....read is initiated when the NOP is transmitted
   {
    while (!(IFG1 & UTXIFG0));
    TXBUF0 = 0x00;                             // What is this? Why I need this? And what it do?  This initiates the SCLK
 
    while (!(IFG1 & URXIFG0));
    STAT0[i] = RXBUF0;                       // What is this? Why I need this? And what it do? sending? STAT0 is a 3 character array, and the SPI RX buffer is stored to the array
   }
 
   for (i = 0; i < 24; i++)                        // Read Channel data // What is this? And what it do? This loop reads 24 bytes of data and stores to the RES0 character array
   {
    while (!(IFG1 & UTXIFG0));
    TXBUF0 = 0x00;                            // What is this? Why I need this? And what it do?
 
    while (!(IFG1 & URXIFG0));
    RES0[i] = RXBUF0;                      // What is this? Why I need this? And what it do? sending?
   }
  
   P2OUT |= ~CS_0;                       // Set CS "high"
  
   configure_uart();                         //config UART
 
   for (i = 15; i < 18; i++)               // Send Channel data to BT // What is this? Why I need this? And what it do? Apparently the original author of the code was communicating to more than one device, in this code snippet you don't see it here, but apparently the second device data was captured and they only transmitted data from channel 6 out the UART
   {
    while (!(IFG1 & UTXIFG0));
    TXBUF0 = RES1[i];                   // What is this? Why I need this? And what it do? This transmits channel 6 out the UART...but in your case it should be RES0[i] 
   // if(rx_on>1 && rx_data==0x00) goto STOP_AD;  // What is this? Why I need this? And what it do? important This is the UART RX command to abort the reading
   }
  
  // rx_on = 0;                               // What is this? Why I need this? And what it do?
   configure_spi();                      // Setup SPI
  }
  
// STOP_AD:                               // What is this? Why I need this? And what it do?
//  rx_on = 0;                               // What is this? Why I need this? And what it do?
 }
}

Best regards,

Bob B

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Dear Kaspars,

                       You can see the content of http://e2e.ti.com/support/data_converters/precision_data_converters/f/73/p/73715/268346.aspx#268346 . Please wait a minute, I will give you the modified code for you.

Hi Kaspars,

                   See th attached files please. 5543.Kaspars.rar

                   The Labview files is for LabVIEW 2009.

Sheng-Fu Chen

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