ADS1298: ADS PROBLEM

Hi Camilo,

Thanks for your post and welcome to the forum!

Are you able to read the device ID correctly?
What does your data collecting routine look like?
Are you sending the correct number of SCLKs for 8 channels of data?
e2e.ti.com/.../2856884

Hi Alexander, thanks for your response.
Answering your questions:
1. Yes, I am. I have read the ADS ID record, obtaining a successful result with address 0x92 of ADS1298.
2. Here is a screenshot with the data. It is written in Python, but the structure is the same in any language, I hope your comments in this section.

#!/usr/bin/python3
# -*- coding: utf-8 -*-

from pickle import dumps
import RPi.GPIO as GPIO
import socket
import spidev
import time

#Definiciones del Socket
#host = '192.168.1.11'
host = '192.168.43.5'
port = 10000
global sock

#Sin alertas de GPIO
GPIO.setwarnings(False)

#Configuración de pines y constantes
PIN_START = 6
PIN_RESET = 12
PIN_DRDY = 24
PIN_CLKSEL = 23
RDATA = 0X12
SDATAC = 0x11
RDATAC = 0X10
START = 0X08
STOP = 0X0A

#Entradas y salidas
GPIO.setmode(GPIO.BCM)
GPIO.setup(PIN_START,GPIO.OUT)
GPIO.setup(PIN_RESET,GPIO.OUT)
GPIO.setup(PIN_CLKSEL,GPIO.OUT)
GPIO.setup(PIN_DRDY,GPIO.IN,pull_up_down=GPIO.PUD_UP)

#Inicializa SPI

spi = spidev.SpiDev()
spi.open(0,0)
spi.lsbfirst = False
spi.max_speed_hz=3000000
spi.mode = 1

#Inicio de variables
GPIO.output(PIN_CLKSEL,GPIO.HIGH)
GPIO.output(PIN_RESET,GPIO.HIGH)

#Envio de datos
time.sleep(0.1)
spi.writebytes([SDATAC])

#Inicializacion de Socket
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print('El socket se creo correctamente')
except socket.error:
print('El socket no pudo se creado')

try:
server_address = (host, port)
sock.connect(server_address)
print('Conectando al servidor %s, por el puerto %s\n' % server_address)

print('Conexion Exitosa!')
except socket.error:
print('El socket no pudo conectar con el servidor')


#Funcion de captura
def captura(channel):
global datos
global contador
spi.writebytes([RDATA])
resp = spi.readbytes(27)
datos = dumps(resp)
print('Datos: %s\n'%resp)
print('Enviando datos...')
sock.sendall(datos)
#contador = contador + 1


#Inicio de captura
time.sleep(0.1)
spi.writebytes([START])

GPIO.add_event_detect(PIN_DRDY,GPIO.FALLING,captura)

try:
time.sleep(600)
except KeyboardInterrupt:
sock.sendall(dumps([]))
sock.close()
finally:
GPIO.cleanup()
sock.sendall(dumps([]))
sock.close()

3. Yes, I think I'm sending the correct data. I'm using Raspberry Pi's SPI interface to do it. I believe that the data is correct because I have been able to read and write several records at the same time, in addition, I have compiled test data that the ADS1298 generates by itself in the 8 channels, modifying the registers 1, 2, 3 and the 8 channels, evidence of this is the 4th image of the last post.

I still have my problem which consists in, when I try to get the ECG signals through the 8 channels, I get no right result at all, so I am looking forward to your advise and support

Thank you so much, Alexander.

Hello Alexander

Thank you very much for attending to my messages. I have to apologize, I erroneously transcribed my code to publish it. I have 0x10 instead of 0x01, which means that all channels work correctly with a gain of 1, but it still does not work.

I have done the exercise of putting in the differential input 2, a test signal of 1 mV which in practice are the RA and LA electrodes as the following figure shows:

As I have metioned you in previews answers, I can not succesfully get the input signal which in this case is the one of 1 mV with 2 hz of frequency. I would like to ask you: Why is that? Perhaps a channel saturation? If so, how can I make sure the said saturation exists and how could I fix it? If it is not a saturation, perhaps could it be something related with the reference signal? In your opinion, am I configurating the reference signal properly? If not, how should I configurate it?

Thank you once again for your help, Alexander!

If the channel was saturated it would produce a full-scale output. Since you can't get any output I'm not too worried about that.

CONF3 Register has 0xEEh. You cannot use a 4V reference with +/-2.5V supplies.
Set CONF3 bit 5 to 0... 0xAEh. Give this a shot.

Try tracing the signal path using the block diagrams and multiplexor switching diagrams to make sure that the signal is correctly passing through. Disabling as many features as you can for now is also a good step.

Additionally, you may want to check this post to verify that your device is functioning: e2e.ti.com/.../2868597