ADS1213 SPI communication problem

Bastien Bordas60

Other Parts Discussed in Thread: ADS1213

Hello!

I need your help about my new Data Converter ADS1213.

I'm trying to start a communication with it through my SPI channel (I'm using an ATMega32).

/* Initialization Pin part */

DDRB = (1<<SCK)|(1<<MOSI); // define my cpu as the Master with SCK and MOSI as output
PORTB = 0x00;

/* SPI: Interrupt disable - SPI enable - MSB first - Master - fosc/16 */
SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR1);

/***************************************/
/* INITIALIZE MY ADS */
/* Clear SPCI */
SPSR;
SPDR;

ADS_ON; // write 0 to my SELADS pin 
//t24 not needed 33.8us without break

SPDR = 0x04;
loop_until_bit_is_set(SPSR,SPIF); // wait the end of the transmit
_delay_us(100);	//t19 for the debug
SPDR = 0x43;   // Use SDOUT for the output
loop_until_bit_is_set(SPSR,SPIF);

ADS_OFF;	//t20 not needed 4.98us without break


/***************************************/
/* TRY TO READ SOMTH */

/* Clear SPI */
SPSR;
SPDR;
	
ADS_ON;
	
/* Read SPI */
SPDR = 0x84; // try to read the Command Register Byte 3
loop_until_bit_is_set(SPSR,SPIF);
_delay_us(100);	//t19 for the debug
SPDR = 0xFF; // wrote 0xFF to get time to read into SDOUT
loop_until_bit_is_set(SPSR,SPIF);
test = SPDR;

ADS_OFF;	//t20 not needed 4.98us without break

And now my diagramm of the ADS:

From the TOP to the BOTTOM:

DRDY

SCK

SDIO

SDOUT

The init sequence with the 2 bytes 0x04 and 0x43

My reading sequence:

Has you can see there is nothing transmit in SDOUT.

Thanks a lot for your futur help.

Do not hesitate if you need more details.

Best,

Bastien

over 10 years ago

0 Bob Benjamin over 10 years ago

TI__Guru** 113765 points

Hi Bastien,

In the second scope shot (reading sequence) notice that the command is incorrect. What is shown is a write sequence and not a read (0x64 instead of 0x84). Notice that the first falling edge of SCLK the SDIO is low, so the INSR is given as write 4 bytes starting at Command Register Byte 3 and write 0xFF. As this is a write sequence, SDOUT will not change.

Best regards,

Bob B

0 Bastien Bordas60 over 10 years ago in reply to Bob Benjamin

Prodigy 80 points

Hi Bob,

Thanks for your answer and it was helping me a lot! I will confirm your answer again after this question.
Now I have some problem to get the response of the ADS. I configure it well because I get the answer througt SDOUT. But Impossible to save it.

I thing the problem is about my Atmega but just in case you see something, I created a small project and test = 0 all the time:

/* Includes */
#include <avr/io.h>
#include <util/delay.h>

/* Define */
typedef unsigned char  u08;
#define TXIN 0.542

/* Macro */
#define set_bit(port, bit)	(port |= (1<<bit))
#define clear_bit(port, bit)	(port &= ~(1<<bit))
#define check_bit(var, pos) ((var) & (1<<(pos)))

/* Variables */
u08 volatile test;

/* Functions */
void ResetADS(void);
void InitADS(void);

int main(void)
{
	/* Init port */
	DDRB = (1<<PINB7)|(1<<PINB5)|(1<<PINB4);
	
	/* Reset the ADS */
	ResetADS();
	
	/* SPI: Interrupt disable - SPI enable - MSB first - Master - fosc/64 */
	SPCR = (1<<SPE)|(1<<MSTR)|(1<<CPHA)|(1<<SPR1);
	
	/* Init the ADS */
	InitADS();
	
	while(1)
	{
		/* Read the configuration */
		/* Clear SPI */
		SPSR;
		SPDR;
	
		loop_until_bit_is_set(PINA, PINA7);
		loop_until_bit_is_clear(PINA, PINA7);
	
		clear_bit(PORTB, PINB4);
	
		/* Read SPI */
		SPDR = 0x87; // read request
		loop_until_bit_is_set(SPSR,SPIF);
		_delay_us(10*TXIN);
		SPDR = 0xFF; // SCK sequence to get the answer
		loop_until_bit_is_set(SPSR,SPIF);
		test = SPDR;
	
		set_bit(PORTB, PINB4);	//t20 not needed 4.98us without break
	}
}

/* Needed when using the ADS as a Slave */
void ResetADS(void)
{
	clear_bit(PORTB, PINB4);
	
	set_bit(PORTB, PINB7);
	_delay_us(1024*TXIN);
	clear_bit(PORTB, PINB7);
	_delay_us(10*TXIN);
	set_bit(PORTB, PINB7);
	_delay_us(512*TXIN);
	clear_bit(PORTB, PINB7);
	_delay_us(10*TXIN);
	set_bit(PORTB, PINB7);
	_delay_us(1024*TXIN);
	clear_bit(PORTB, PINB7);
	_delay_us(10*TXIN);
	set_bit(PORTB, PINB7);
	_delay_us(2048*TXIN);
	clear_bit(PORTB, PINB7);
	
	set_bit(PORTB, PINB4);
}

/* Configure the MISO as the ADS output */
void InitADS(void)
{
	/* Clear SPI */
	SPSR;
	SPDR;
	
	loop_until_bit_is_set(PINA, PINA7);
	loop_until_bit_is_clear(PINA, PINA7);
	
	clear_bit(PORTB, PINB4);	// t24 not needed 33.8us without break

	/* Read SPI */
	SPDR = 0x04;	// Write CMR Byte 3
	loop_until_bit_is_set(SPSR,SPIF);
	SPDR = 0x42;	// SDOUT for the output
	loop_until_bit_is_set(SPSR,SPIF);

	set_bit(PORTB, PINB4);	// t20 not needed 4.98us without break
}

I also made a measure:

Signals in order: 3: DRDY, 4: SELADS, 0: SCK, 1: MOSI, 2: MISO from the ADS

and the Yellow PINB6 MISO from the Atmega

Thn

Thanks again,

Best,

Bastien

0 Bob Benjamin over 10 years ago in reply to Bastien Bordas60

TI__Guru** 113765 points

Hi Bastien,

I don't see anything wrong with your code unless it is in the function loop_until_bit_is_set(). If you are using a debugger to check the value of the test variable, it is possible that the debugger is not handling the values/locations properly depending on where you set the breakpoint. The breakpoint should come after the completion of the command to set test to SPDR.

Best regards,

Bob B

0 Bastien Bordas60 over 10 years ago in reply to Bob Benjamin

Prodigy 80 points

Hi!

Good news, I received another experimental board today, I tested the same out with it... and suprise everything works fine!

So I think my Atmega pin should be dead :(.

Best and thanks again for your help!

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ADS1213 SPI communication problem