ADS1298: SPI not reading

Naveen S

Part Number: ADS1298

Tool/software:

I keep getting 0x00 for all register reads the ads1298 is connected to the STM32WB55 board, with the DRDY pin remaining high everytime.. it never goes down, but I do not get any errors on SPI transactions either.
SPI configs:
Data size 8 bits
MSB first
Prescaler - 128 , baudrate - 250kb/s
CPOL - low
CPHA - 1 edge

The code:
ads1298.c:

#include "ads1298.h"

#include "main.h" // For hspi1

#include <stdio.h>



// External SPI handle

extern SPI_HandleTypeDef hspi1;



// Send SPI command

static void ADS1298_SendCommand(uint8_t cmd)

{

 uint8_t rx[1] = {0};

 ADS1298_CS_LOW();

 HAL_Delay(1); // Ensure 2 µs minimum (t_SDECODE)

 HAL_StatusTypeDef status = HAL_SPI_TransmitReceive(&hspi1, &cmd, rx, 1, 1000);

 ADS1298_CS_HIGH();

 HAL_Delay(1); // Wait 4 t_CLK (~2 µs) before next command

 printf("Command 0x%02X sent, RX: 0x%02X, Status: %d, Error: %ld\r\n", cmd, rx[0], status, HAL_SPI_GetError(&hspi1));

}



// Write register

void ADS1298_WriteRegister(uint8_t reg, uint8_t val)

{

 ADS1298_CS_LOW();

 HAL_Delay(1); // Ensure 2 µs minimum

 HAL_SPI_Transmit(&hspi1, (uint8_t[]){ADS_WREG | reg, 0x00, val}, 3, 1000); // Single register write

 ADS1298_CS_HIGH();

 HAL_Delay(1); // Wait 4 t_CLK (~2 µs)

 printf("Wrote Reg 0x%02X with 0x%02X\r\n", reg, val);

}



// Read register

uint8_t ADS1298_ReadRegister(uint8_t reg)

{

 uint8_t rx[3] = {0};

 ADS1298_CS_LOW();

 HAL_Delay(1); // Ensure 2 µs minimum

 HAL_SPI_Transmit(&hspi1, (uint8_t[]){ADS_RREG | reg, 0x00, 0xFF}, 3, 1000); // Read one register

 ADS1298_CS_HIGH();

 HAL_Delay(1); // Wait 4 t_CLK (~2 µs)

 printf("Read Reg 0x%02X: RX: 0x%02X 0x%02X 0x%02X, Value: 0x%02X\r\n",

 reg, rx[0], rx[1], rx[2], rx[2]);

 return rx[2];

}



// In ADS1298_Init

void ADS1298_Init(void)

{

 printf("ADS1298 Initialization Started\r\n");



 HAL_GPIO_WritePin(GPIOB, GPIO_PIN_7, GPIO_PIN_SET); // PWDN HIGH

 HAL_GPIO_WritePin(GPIOB, GPIO_PIN_6, GPIO_PIN_RESET); // RESET LOW

 HAL_Delay(1); // 1 µs

 HAL_GPIO_WritePin(GPIOB, GPIO_PIN_6, GPIO_PIN_SET); // RESET HIGH

 printf("RESET Applied\r\n");



 HAL_Delay(100); // Reduced from 1000 ms for testing

 printf("Post-RESET Delay Complete\r\n");



 ADS1298_SendCommand(ADS_RESET); // Software reset

 HAL_Delay(1); // 1 ms

 printf("SPI RESET Sent\r\n");



 ADS1298_SendCommand(ADS_SDATAC); // Stop continuous mode

 HAL_Delay(1); // 1 ms

 printf("SDATAC Sent\r\n");



 uint8_t id = ADS1298_ReadRegister(ADS_REG_ID);

 uint8_t config2 = ADS1298_ReadRegister(ADS_REG_CONFIG2);

 int channels = 0;

 switch (id & 0x1F) {

 case 0x10: channels = 4; break;

 case 0x11: channels = 6; break;

 case 0x12: channels = 8; break;

 case 0x1E: channels = 8; break;

 default: channels = 0;

 }

 printf("Device ID: 0x%02X, Channels: %d, CONFIG2: 0x%02X\r\n", id, channels, config2);





 ADS1298_SendCommand(ADS_START);

 HAL_Delay(1); // 1 ms

 printf("START Sent\r\n");



 if (ADS1298_DRDY() == GPIO_PIN_SET) {

 printf("DRDY is HIGH (device may not be ready)\r\n");

 } else {

 printf("DRDY is LOW (device ready)\r\n");

 }



 printf("ADS1298 Initialization Complete\r\n");

}






ads1298.h:

#ifndef APPLICATION_USER_STM32_WPAN_APP_ADS1298_H_

#define APPLICATION_USER_STM32_WPAN_APP_ADS1298_H_



#include "stm32wbxx_hal.h"

#include <stdio.h>



// ADS1298 SPI commands

#define ADS_WAKEUP 0x02

#define ADS_STANDBY 0x04

#define ADS_RESET 0x06

#define ADS_START 0x08

#define ADS_STOP 0x0A

#define ADS_RDATAC 0x10

#define ADS_SDATAC 0x11

#define ADS_RDATA 0x12

#define ADS_RREG 0x20

#define ADS_WREG 0x40



// ADS1298 Register Addresses (only relevant ones for now)

#define ADS_REG_ID 0x00

#define ADS_REG_CONFIG2 0x02



// Pin definitions

#define ADS1298_CS_LOW() HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_RESET) // PA4

#define ADS1298_CS_HIGH() HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_SET)

#define ADS1298_START_HIGH() HAL_GPIO_WritePin(GPIOE, GPIO_PIN_4, GPIO_PIN_SET) // PE4

#define ADS1298_START_LOW() HAL_GPIO_WritePin(GPIOE, GPIO_PIN_4, GPIO_PIN_RESET)

#define ADS1298_DRDY() HAL_GPIO_ReadPin(GPIOA, GPIO_PIN_15) // PA15



// Functions

void ADS1298_Init(void);

void StartEcgPrintTask(void *argument);

uint8_t ADS1298_ReadRegister(uint8_t reg);

void ADS1298_WriteRegister(uint8_t reg, uint8_t val);



#endif /* APPLICATION_USER_STM32_WPAN_APP_ADS1298_H_ */

Where did I go wrong?

5 days ago

0 Ryan Andrews 4 days ago

TI__Guru 66566 points

Hi Naveen,

Thank you for your post.

Are you following the recommended initialization sequence in section 10.1? Power supply ramping and power-on reset is also described in Section 11, which is recommended to ensure the ADS1298 is initialized properly.

In order to read/write registers, you will first need to send the SDATAC command.

For multi-byte transactions, it is necessary to keep /CS low throughout the SPI frame.

Regards,

Ryan

0 Naveen S 3 days ago in reply to Ryan Andrews

Prodigy 10 points

void ADS1298_Init(void)
{
    printf("ADS1298 Initialization Started\r\n");

    // Power-On Reset Sequence
    ADS1298_PWDN_LOW();    // PWDN low during power-up
    HAL_Delay(100);        // Allow power stabilization
    ADS1298_PWDN_HIGH();   // PWDN high
    HAL_Delay(100);        // Transition time

    ADS1298_RESET_LOW();   // RESET low
    HAL_Delay(10);         // 10 ms > 0.976 µs
    ADS1298_RESET_HIGH();  // RESET high
    HAL_Delay(1000);       // ≥1s for oscillator stabilization

    printf("Power-On and RESET Sequence Complete\r\n");

    // Verify SPI
    if (hspi1.State != HAL_SPI_STATE_READY) {
        printf("SPI not ready, State: %d\r\n", hspi1.State);
        return;
    }
    printf("SPI initialized correctly\r\n");

    // Check control pin states
    printf("PWDN: %d, RESET: %d, START: %d, DRDY: %d\n",
           HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_7),
           HAL_GPIO_ReadPin(GPIOB, GPIO_PIN_6),
           HAL_GPIO_ReadPin(GPIOE, GPIO_PIN_4),
           ADS1298_DRDY());

    // Send SDATAC to stop read-continuous mode
    uint8_t sdatac_response = ADS1298_SendCommand(ADS1298_CMD_SDATAC);
    printf("SDATAC Response: 0x%02X\r\n", sdatac_response);
    HAL_Delay(10);

    // Configure CONFIG1 (example: 250 SPS)
    uint8_t config1[] = {ADS1298_CMD_WREG | ADS1298_REG_CONFIG1, 0x00, 0x00}; // 250 SPS
    ADS1298_CS_LOW();
    HAL_SPI_Transmit(&hspi1, config1, 3, 1000);
    ADS1298_CS_HIGH();
    HAL_Delay(10);

    // Set START pin and send START command
    if (HAL_GPIO_ReadPin(GPIOE, GPIO_PIN_4) != GPIO_PIN_SET) {
        ADS1298_START_HIGH();
        printf("START forced HIGH\r\n");
    }
    uint8_t start_response = ADS1298_SendCommand(ADS1298_CMD_START);
    printf("START Response: 0x%02X, DRDY: %d\n", start_response, ADS1298_DRDY());
    HAL_Delay(100);

    // Verify initialization
    ADS1298_ReadID();
    ADS1298_ReadConfig1();
    ADS1298_ReadConfig2();
    printf("ADS1298 Initialization Complete\r\n");
}

This is my initialization code.. hope this follows the sequence.. still the spi reads 0x00.. should I check the power supply to ads1298??

0 Naveen S 1 day ago in reply to Naveen S

Prodigy 10 points

Ryan Andrews

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ADS1298: SPI not reading