ADS1291 have problem retrieving converted data

wang po shen

Intellectual 260 points

Other Parts Discussed in Thread: ADS1291, MSP430F5529, MSP430F5522

hello everyone.

i have problem retrieving converted data from ADS1291.

this is my ADS1291 Circuit.

and i have already test this ADS1291 Circuit on bread board with MSP430F5529 development board.

and it's can work perfectly.

But now. i am using ADS1291 external CLK=2.048MZ and SPI CLOCK=4MHZ with MSP430F5522 , and i have MSP430F5522 external CLK=8MHZ.

and i found that i can't read/write ADS1291 correctly.

and after some try and error.

i found that i can write/read ADS1291 register correctly if i add a delay when i write ADS1291 register.

here is my MSP430F5522 source code

#include <msp430f5529.h>
#include <math.h>

#define   START            0x80         // P2.7
#define   PWDN             0xFE         // P2.0
#define   RESET_BT         0xBF         // P2.6
#define   DRDY_0           0x02         // P2.1
#define   CS_0             0xEF         // P4.4

char STAT0[3], RESU0[24], STAT1[3], RESU1[24];
char LOFF_P0, LOFF_N0, LOFF_P1, LOFF_N1, header, rx_data, rx_on=0, tx_on=0;

void configure_uart(void)
{
P3SEL |= BIT3 + BIT4;                     // P3.3,4 = USCI_A0 TXD/RXD
UCA0CTL1 |= UCSWRST;                      // **Put state machine in reset**
UCA0CTL1 |= UCSSEL_2;                     // SMCLK
UCA0BR0 = 0x08;                           // 8MMHz 921600 (see User's Guide)
UCA0BR1 = 0x00;                           // 8MMHz 921600
UCA0MCTL |= UCBRS_6 + UCBRF_8;            // Modulation UCBRSx=1, UCBRFx=0
UCA0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine**
UCA0IE |= UCRXIE;                         // Enable USCI_A0 RX inter
}

void configure_spi(void)                    //在這邊設定port4(解多工器) P4DIR P4OUT
{
                                            // P1DIR |= 0x80 P1.7 for RESET_ADS
P2DIR |= 0XC1;                            // P2.0, 6, 7 for PWDN, RESET_BT, START
P3SEL |= BIT0 + BIT1 + BIT2;              // P3.0, 1, 2 SPI option select
P4DIR |= 0X1F;
P4OUT |= ~CS_0 ;

UCB0CTL1 |= UCSWRST;                      // **Put state machine in reset**
UCB0CTL0 |= UCMST+UCSYNC+UCMSB;           // 3-pin, 8-bit SPI master, MSB
UCB0CTL1 |= UCSSEL_2;                     // SMCLK
UCB0BR0 = 0x02;                           // /2
UCB0BR1 = 0x00;                           //
UCB0CTL1 &= ~UCSWRST;                     // **Initialize USCI state machine*
}

void main(void)
{
char i;

WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT

P5SEL |= BIT2+BIT3;                       // Port select XT2

UCSCTL6 &= ~XT2OFF;                       // Enable XT2
UCSCTL3 |= SELREF_2;                      // FLLref = REFO
                                            // Since LFXT1 is not used,
                                            // sourcing FLL with LFXT1 can cause
                                            // XT1OFFG flag to set
UCSCTL4 |= SELA_2;                        // ACLK=REFO,SMCLK=DCO,MCLK=DCO

// Loop until XT1,XT2 & DCO stabilizes - in this case loop until XT2 settles
do
{
    UCSCTL7 &= ~(XT2OFFG + XT1LFOFFG + DCOFFG);
                                            // Clear XT2,XT1,DCO fault flags
    SFRIFG1 &= ~OFIFG;                      // Clear fault flags
}while (SFRIFG1&OFIFG);                   // Test oscillator fault flag

UCSCTL6 &= ~XT2DRIVE0;                    // Decrease XT2 Drive according to
                                            // expected frequency
UCSCTL4 |= SELS_5 + SELM_5;               // SMCLK=MCLK=XT2

configure_uart();
configure_spi();                      // Setup SPI

P2OUT &= PWDN;                           //PWDN = 0
P2OUT &= RESET_BT;                     // P2.6 RESET_BT
P2OUT &= ~START;                         //START = 0
P2OUT |= ~PWDN;                          //PWDN = 1


P4OUT &= CS_0;                        // CS=0 CS Enable

while (!(UCB0IFG&UCTXIFG));            // SDATAC
UCB0TXBUF = 0x11;

while (!(UCB0IFG&UCTXIFG));             //從01h開始寫
UCB0TXBUF = 0x41;

while (!(UCB0IFG&UCTXIFG));             //寫3個暫存器
UCB0TXBUF = 0x02;

for (i = 0; i < 10; i++);

while (!(UCB0IFG&UCTXIFG));       // WREG CONFIG1 0x03   00000011 continuous mode, Data rate = 1KSPS
UCB0TXBUF = 0x03;

for (i = 0; i < 10; i++);

while (!(UCB0IFG&UCTXIFG));             // WREG CONFIG2 0xA0   10100000 internal reference 2.4 V
UCB0TXBUF = 0xA0;

while (!(UCB0IFG&UCTXIFG));             // WREG Lead-Off Control Register 0x10   00010000
UCB0TXBUF = 0x10;

while (!(UCB0IFG&UCTXIFG));            //從04h開始寫
UCB0TXBUF = 0x44;

while (!(UCB0IFG&UCTXIFG));            //寫兩個暫存器
UCB0TXBUF = 0x01;

while (!(UCB0IFG&UCTXIFG));             // WREG CH1     0x10   00010000
UCB0TXBUF = 0x10;

while (!(UCB0IFG&UCTXIFG));             // WREG CH2     0x81   10000001   power down CH2
UCB0TXBUF = 0x81;

while (!(UCB0IFG&UCTXIFG));             //從08h開始寫
UCB0TXBUF = 0x48;

while (!(UCB0IFG&UCTXIFG));            //寫一個暫存器
UCB0TXBUF = 0x00;

while (!(UCB0IFG&UCTXIFG));            //    01000000   CLK_DIV = 1 , CLK = 2.048MHZ
UCB0TXBUF = 0x40;

while (!(UCB0IFG & UCTXIFG)); // RREG starting at address 1 00100001 01h 開始讀
UCB0TXBUF = 0x21;
while (!(UCB0IFG & UCTXIFG)); // 讀8個 Registers
UCB0TXBUF = 0x07;
while (!(UCB0IFG & UCTXIFG)); // first dummy data
UCB0TXBUF = 0x00;
while (!(UCB0IFG & UCTXIFG)); // another dummy data
UCB0TXBUF = 0x00;
while (!(UCB0IFG & UCRXIFG));
RES[0] = UCB0RXBUF;
while (!(UCB0IFG & UCTXIFG));
UCB0TXBUF = 0x00;
while (!(UCB0IFG & UCRXIFG));
RES[1] = UCB0RXBUF;
while (!(UCB0IFG & UCTXIFG));
UCB0TXBUF = 0x00;
while (!(UCB0IFG & UCRXIFG));
RES[2] = UCB0RXBUF;
while (!(UCB0IFG & UCTXIFG));
UCB0TXBUF = 0x00;
while (!(UCB0IFG & UCRXIFG));
RES[3] = UCB0RXBUF;
while (!(UCB0IFG & UCTXIFG));
UCB0TXBUF = 0x00;
while (!(UCB0IFG & UCRXIFG));
RES[4] = UCB0RXBUF;
while (!(UCB0IFG & UCTXIFG));
UCB0TXBUF = 0x00;
while (!(UCB0IFG & UCRXIFG));
RES[5] = UCB0RXBUF;
while (!(UCB0IFG & UCTXIFG));
UCB0TXBUF = 0x00;
while (!(UCB0IFG & UCRXIFG));
RES[6] = UCB0RXBUF;
while (!(UCB0IFG & UCTXIFG));
UCB0TXBUF = 0x00;
while (!(UCB0IFG & UCRXIFG));
RES[7] = UCB0RXBUF;

while(UCB0STAT & UCBUSY);           //SPI 如果UCBUSY=0 閒置如果UCBUSY=1 USCI 正在接受或傳輸

_EINT();

P2OUT |= ~RESET_BT;

while(1)                              //把 NOSTOP 和 STOP_AD 包含住
{
   while(rx_on==0);                     //rx_on=0 留在迴圈 rx_on不等於0 離開迴圈
   rx_on = 0;
   if(rx_data==0xff) goto NOSTOP;       //電腦透過RS232 UART 傳開始字元 FF 給UART RX BUFFER
   goto STOP_AD;

NOSTOP:
   header = 0;
   P2OUT |= START;                       //START=1 開始做ADC轉換

   while (!(UCB0IFG&UCTXIFG));           // RDATAC
   UCB0TXBUF = 0x10;

   while(1)                       //進入NOSTOP迴圈後便一值讀出ADC資料直到UART 中斷為止(STOP_AD)
   {
    while((P2IN & DRDY_0));       //P2.1 DRDY_0 是否為LOW ?   如果為LOW 則跳出迴圈(ADC資料準備好了)

    for (i = 0; i < 3; i++)      // Read Status register 會先傳狀態暫存器總共三筆 3*8=24BITS
    {
     while (!(UCB0IFG&UCTXIFG));
     UCB0TXBUF = 0x00;

     if(UCB0STAT & UCOE)
     {
      while (!(UCB0IFG&UCRXIFG));
      STAT0[0] = UCB0RXBUF;
     }

     while (!(UCB0IFG&UCRXIFG));
     STAT0[i] = UCB0RXBUF;                //i=0,1,2 三筆狀態資料
    }

    for (i = 0; i < 6; i++)       // Read Channel data 再傳CH值 ADS1291 2CH *24BITS=48BITS 一次傳8BITS
    {
     while (!(UCB0IFG&UCTXIFG));
     UCB0TXBUF = 0x00;

     while (!(UCB0IFG&UCRXIFG));         //ADS:MSB UART:LSB SPI:MSB
     RESU0[i] = UCB0RXBUF;
    }

    RESU0[2]=RESU0[2] & 0xFE;
    RESU0[2]=RESU0[2] | header;
    header++;
    if ( header == 2 ) header = 0;

    for (i = 0; i < 3; i++)              // Send Channel data to BT 傳一個CH的DATA 只有傳CH1 DATA
    {
     while (!(UCA0IFG&UCTXIFG));         // USCI_A0 TX buffer ready?
     UCA0TXBUF = RESU0[i];               // i=0,1,2
     if(rx_on>0 && rx_data==0x00) goto STOP_AD;    //如果發生UART中斷命令停止ADC取樣則rx_on大於0 且 rx_data=0x00
    }
    while(UCA0STAT & UCBUSY);
    rx_on = 0;
   }                                              //繼續 NOSTOP While(1) 迴圈
STOP_AD:
   rx_on = 0;
}
}

#pragma vector=USCI_A0_VECTOR
__interrupt void USCI_A0_ISR(void)    //P997 UART 中斷   猜想是電腦透過RS232 UART傳資料給RX Buffer 造成RX中斷
{
   rx_data = UCA0RXBUF;               //UART 使用 FF當作開始字元 00當作結束字元
   rx_on++;
}

can anyone explain why after i add for (i = 0; i < 10; i++); this delay when i wrote ADS1291 register then i can write/read ADS1291 register correctly?

and did i have something wrong with ADS1291 register setting?

and at the end. i sent those converted data by Bluetooth using 921600 baudrate.

and accept those data by Labview.

My Ads1291 IN1P is connetted to the output of analog amp including one INA and OPA and shift the signal to 1.5V.

my total analog amp gain = 3315

and i have already check my analog part, which is perfect.

here are the outcome i got from ADS1291.

100mVPP 5HZ sin wave

100mVPP 10HZ sin wave

200mVPP 5HZ sin wave

200mVPP 10HZ sin wave

300mVPP 5HZ sin wave

300mVPP 10HZ sin wave

so have anyone know why i got this outcome?

are there any problem about my Firmware or my circuit?

Needs your help.

thanks for all of you.

over 13 years ago

0 Greg Hupp over 13 years ago

TI__Mastermind 23235 points

Mr Shen -

Have you noted the decode times for the Multi-byte commands (see page 10 and 37-38 of the datasheet). When you run at a faster clock, you may be violating the decode time which is why the delay may work.

0 wang po shen over 13 years ago in reply to Greg Hupp

Intellectual 260 points

yes i notice that.

but even i can write/read the ADS1291 successfully

i still can't read the correct converted data from ADS1291.

do you have any idea why ?

thank you very much

0 Greg Hupp over 13 years ago in reply to wang po shen

TI__Mastermind 23235 points

Mr Shen -

A couple of questions -

1. When you read back the data and get "bad" data, what indicates to you that the data is not valid? The reason for the question is that perhaps the data is valid and the device is not configured the way you are expecting? You might want to verify the settings, especially if you are reading and writing registers correctly.

2. when you communicate with the device, are you doing the 24bit transfers all at once or in multiple chunks (ie 3 x 8bits -> see Figure 45/46 in datasheet)? You might also note the Serial Clock (SCLK) section in the applications section of the data sheet to make sure the SCLK requirements are correct.

0 wang po shen over 13 years ago in reply to Greg Hupp

Intellectual 260 points

HI Greg.

1. i am using function generator to sent a sin wave and then have the singal divided by 1000 .

and the divided singal go threw an analog amplifer . which totally gain=3310

and then the amplifed singal connected to ADS1291 IN1P .

i have already check the analog part . the analog signal is ok.

should i post my whole circuit include the analog part to you?

and my ADS1291 registers settings are

CONFIG1 0x03

CONFIG2 0xA0

Lead-Off Control Register 0x10

CH1 0x10

CH2 0x81

LOFF_STAT 0x40

RESP1 0x02

i am only using the A/D function.

did i miss any register setting? or have some registers setting wrong?

and i already check all the register are writen/read correctly.

2. sorry i really don't know what " doing the 24bit transfers all at once or in multiple chunks " this mean.

can you explain more detail to me?

thank you Greg

0 Greg Hupp over 13 years ago in reply to wang po shen

TI__Mastermind 23235 points

Mr Shen -

The settings appear to be correct; so you are probably good there.

Regarding #2, (referring to Fig 45/46)... in our evaluations, usually divide the write/read back up into 8 bit chunks. ie Instead of doing a 24bit continuous SCLK, you can do a 8bit SCLK transfer x 3 to get all 24bits. This helps out with some of the timing requirements.

One additional question, have you actually probed your input signal to verify that the input to the ADC is OK and not distorted or not what you would expect? From your statements, a gain of 3315 seem VERY high, so we want to make sure that there isn't a problem there. Also, since you are running the part at the lower Vref range (2.4V), make sure that you signal is not greater than +/-2.4V.

0 wang po shen over 13 years ago in reply to Greg Hupp

Intellectual 260 points

hi Greg. thank you.

Sorry. i am not good at coding . Can i post my retrieving data part of Firmware and help me to separate 24bit continuous SCLK into 3x 8 bit continuous SCLK?

and the second question.

Yes. i have already probe the output of analog part.

and i just come up a question in my mind.

because my common voltage is 1.5V . so that means the Maxima amplitude of the sin wave input to ADS1291 = 2.4-1.5=0.9V?

thanks a lot

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ADS1291 have problem retrieving converted data