ADS1218: Code examples of ADS1218

Hi Bob,

Thank you very much for your reply. The code examples you provided help me a lot. Now, I am carring out experimentation with the ADS1218 . And I will post the final code if the test is ok.

Best regards,

Hi Bob,

I am sorry to bother you again. Recently I start to test the ADS1218 with MSP430F149. However,  the ADC does not work. I configure the ADC SETUP register and set the voltage reference out as 1.25V. But the voltage reference output is always 2.5V.  I found the SPI works well by using oscilloscope to observe the DOUT, DIN, SCLK, CS line when I send the command. The power supply of ADC is 3V. The POL pin of ADC is set high. And the SPI program and ADC configure program list below. Can you give some advice for this problem, thank you very much.

//******SPI initialization code*******//

#include <msp430x14x.h>

#include "SPI.h"

void SPI_Init()

{

// Set the pin as USART port

  P3SEL|=BIT1+BIT2+BIT3;

// Stop USART  

  UCTL0|=SWRST;    

// 8 bit mode, SPI Master

  UCTL0|=CHAR+SYNC+MM;    

// Chosse SMCLK as USART clock, in this program, the SMCLK=1MHz

  UTCTL0|=SSEL1;  

// Set the SCLK=100kHz  

  UBR00=0x0A;

  UBR10=0x00;

// Disable UMCTL0 in SPI master mode  

  UMCTL0=0x00;

// 3-wire SPI  

  UTCTL0|=STC;      

// Configure SCLK phase and polarity, 01

  UTCTL0&=~(CKPH);

  UTCTL0|=CKPL;  

// Enable USART module  

  U0ME=USPIE0;    

  UCTL0&=~SWRST;  

// Enable transimit and receive interrupt  

  IE1|=URXIE0+UTXIE0;  //使能发送和接收中断

}

//********ADS1218 initialization and configure code*******//

//

//               MSP430F149

//          -------------------

//          |                  |

//          |                  |

//          |             P3.6 |<--DRDY

//          |                  |        

//          |             P3.3 |-->SCLK        

//          |                  |

//          |             P3.2 |<--SOMI(DOUT)

//          |                  |

//          |             P3.1 |<--SIMO(DIN)

//          |                  |

//          |             P3.0 |-->CS

//          |                  |

//          |                  |

//          -------------------    

//

//

//            

//            Date: 2017/09/26

#include <msp430x14x.h>

#include "ADS1218.h"

#include "Delay.h"

void ADS1218_Init()

{

 ADS1218_CSHigh;   // Disable ADS1218

 P3DIR|=BIT0;      // CS pin of ADS1218

 P3DIR&=~BIT6;     // DRDY pin of ADS1218  

}

void ADS1218_Config()

{

 unsigned char Temp;

 Temp=ADS1218P0|ADS1218NCOM;

 ADS1218_WRReg(ADS1218_MUX,0x01,&Temp); //Chosse channel AIN0-Acom

 Temp=REFEN;                      // IRV=1.25V, fmod=fosc/128, Buffer Disabled, MSB Transmitted First

 Temp&=~REFHI;

 ADS1218_WRReg(ADS1218_SETUP,0x01,&Temp);

 Temp=ADS1218PGA1;

 ADS1218_WRReg(ADS1218_ACR,0x01,&Temp);

 Temp=SMODE3|UB|0x03;                  // Select sinc3 filter, unbiopolar data format, decimation high 3bits

 ADS1218_WRReg(ADS1218_DEC1,0x01,&Temp);

 Temp=0xFF;

 ADS1218_WRReg(ADS1218_DEC0,0x01,&Temp);

}

void ADS1218_WRReg(unsigned char StartAddress, unsigned char NumReg, unsigned char *pData)

{

 unsigned char i;

 ADS1218_CSLow;

 ADS1218_Send(WREG|(StartAddress&0x0F));

 ADS1218_Send((NumReg-1)&0x0F);

 for (i=0;i<NumReg;i++)

 {

   ADS1218_Send(*pData++);

 }

 ADS1218_CSHigh;

}

void ADS1218_Send(unsigned char Data)

{

 unsigned char dummy;

 while (!UTXIFG0);

 TXBUF0=Data;

 while(!URXIFG0);  

 dummy=RXBUF0;

 //delay 8 time of SCLK frequency

 delay_us(80);

}

//********The circuit diagram of ADS1218 and MSP430F149*********//

Hi user4908522,

You have given a lot of useful information.  However, with respect to communication it would be helpful for me to actually see logic analyzer of oscilloscope shots of the communication; in particular, CS, SCLK, DIN and DOUT.  CS must go low and stay low throughout the entire communication transaction.  Based on the information it would appear that the ADS1218 is not responding to the communication.  The first place to start is to read the registers first to see if you get the default power up values.  You also need to check that all power supply connections to the ADS1218 are valid (both analog and digital supplies), and RESET, PDWN, DSYNC pins are high.  Also, you must have a valid clock, so verify that the crystal is truly oscillating.

Best regards,

Bob B

Hi Bob,

I had check all the points you mentioned above again and everything is ok. Then I run the code step by step, the voltage reference output become 1.25v just same as setting value. However, if I run all the code at once , the voltage reference output become 2.5v. It seems too weird. I doubt the the delay time in SPI Send and Receive function is too short. Therefore, I set the delay time from 80us to 200us in Send and Receive function (the SCLK is 100kHz) , however, this phenomenon still exist.

Best regards

Hi user4908522,

I'm glad to hear you found the issue.  Thanks for responding and sharing your solution.  This may help others with similar issues in the future.

Best regards,

Bob B