ADS1299 EVM Board single-ended measurement set up

joaquin sanchez

Other Parts Discussed in Thread: ADS1299

This question is regarding the ADS1299 Evaluation Modules. I am successfully getting 2 channel differential measurements with bias drive electrode. The register set up for this measurement is as follows:

ads_wreg(CONFIG1, 0x95);

ads_wreg(CONFIG2, 0xC0);

ads_wreg(CONFIG3, 0xEC); // Sets BIASREF signal sorce to (AVDD - AVSS)/2

ads_wreg(LOFF, 0x00);

ads_wreg(CH1SET, 0x60);

ads_wreg(CH2SET, 0x60);

ads_wreg(CH3SET, 0x60);

ads_wreg(CH4SET, 0x60);

ads_wreg(CH5SET, 0x60);

ads_wreg(CH6SET, 0x60);

ads_wreg(CH7SET, 0x60);

ads_wreg(CH8SET, 0x66); // sets this channel the bias driver. Right leg driver

ads_wreg(BIAS_SENSP, 0x0C);

ads_wreg(BIAS_SENSN, 0x0C);

ads_wreg(LOFF_SENSP, 0xFF); // Sense bias from channel 3 & 4

ads_wreg(LOFF_SENSN, 0xFF);

ads_wreg(LOFF_FLIP, 0xFF);

ads_wreg(LOFF_STATP, 0x00);

ads_wreg(LOFF_STATN, 0x00);

ads_wreg(GPIO, 0x00);

ads_wreg(MISC1, 0x00);

ads_wreg(MISC2, 0x00);

ads_wreg(CONFIG4, 0x00);

A soon as I try to make single ended measurements, I am having trouble acquiring the ECG. I would like to get data from 3 channels, all single-ended measurments, with respect to a reference electrode and also a Bias Drive electrode connected to the right leg.

ads_wreg(CONFIG1, 0x95);

ads_wreg(CONFIG2, 0xC0);

ads_wreg(CONFIG3, 0xEC);

ads_wreg(LOFF, 0x00);

ads_wreg(CH1SET, 0x60);

ads_wreg(CH2SET, 0x60);

ads_wreg(CH3SET, 0x60);

ads_wreg(CH4SET, 0x60);

ads_wreg(CH5SET, 0x60);

ads_wreg(CH6SET, 0x60);

ads_wreg(CH7SET, 0x68);

ads_wreg(CH8SET, 0x66);

ads_wreg(BIAS_SENSP, 0x0E);

ads_wreg(BIAS_SENSN, 0x0E);

ads_wreg(LOFF_SENSP, 0xFF);

ads_wreg(LOFF_SENSN, 0xFF);

ads_wreg(LOFF_FLIP, 0xFF);

ads_wreg(LOFF_STATP, 0x00);

ads_wreg(LOFF_STATN, 0x00);

ads_wreg(GPIO, 0x00);

ads_wreg(MISC1, 0x20);

ads_wreg(MISC2, 0x00);

ads_wreg(CONFIG4, 0x00);

For my single-ended measurement the register changes are as follows:

CH7SET is set to 0x68, as I set this channel to be my reference electrode, changes the the SRB2 bit to 1

MISC2 register that sets the SRB1 bit to 1 which connects all the inverting inputs to SRB1 (needed for single ended measurements)

I have played a little with the jumpers to no avail. Page 17 of the manual says to short pin 5 and 6 of JP25. In addition in page 34, it states the the EVM needs to have pins 2 and 3 of JP7 and JP8 connected . Is there any other jumper that I am not taking into account? Could it be a problem with the registers? If anybody successfully managed to perform this kind of measurement please share your set up with me.

Kind regards,

Joaquin

over 11 years ago

0 joaquin sanchez over 11 years ago

Prodigy 20 points

I have doubled checked my registers multiple times and I think they are not the problem. I am not entirely sure about the jumpers. Could anybody tell me the right position of the all the jumpers for a single ended measurement?

0 Ryan Andrews over 11 years ago in reply to joaquin sanchez

TI__Guru 66256 points

Hi Joaquin,

Your jumper settings sound correct; however, I should point out that since you are taking Channel 7 positive (IN7P) to be your reference electrode, you do not need JP25 [5-6] connected. The intention of JP25 [5-6] is to connect BIAS_ELEC (the output of the BIAS amplifier) to REF_ELEC, which could then be buffered by U4 or routed directly to SRB1. Instead, you are replacing REF_ELEC with IN7P and that's ok.

Is the Channel 7 electrode separate from BIAS_ELEC? I do not believe the same bias signal that drives the patient is commonly used as the reference for single-ended measurements.

What do your input and output waveforms look like? Try testing your setup with a small 1kHz sine wave input (maybe +/- 50 mV) and probe the SRB1 and SRB2 pins.

Regards,

0 Juan Sousa over 11 years ago

Prodigy 110 points

Hi Joaquin sanchez,

I'm trying to do the same work measurement, however unsuccessfully. I wish I could see your code and how to use this microcontroller to obtain the data.

Best Regards...

0 Juan Sousa over 11 years ago in reply to Ryan Andrews

Prodigy 110 points

I'm trying to get data from the ADS1299 starting the teensy 3.1 device, I can write in the registers successfully, however when I RDATAC to get the values I am not getting correct data, after that I see the values of the registers again and are not as configured by I previously.

the code to WREG and rreg is as follows (teensy):

if ((val >= 0x20) && (val <= 0x3F)) { //RREG (Read register) command
for (int i = 0; i < 10; ++i) if (Serialavailable(serialNum) < 1) delay(1);
if(Serialavailable(serialNum) < 1) return;
unsigned char numSerialBytes = Serialread(serialNum)+1;
digitalWrite(IPIN_CS, LOW);
SPI.transfer(val);
SPI.transfer(numSerialBytes-1); // number of registers to be read – 1
unsigned char serialBytes[numSerialBytes];
for (int i = 0; i < numSerialBytes; ++i)
serialBytes[i] =SPI.transfer(0);
delayMicroseconds(1);
digitalWrite(IPIN_CS, HIGH);
switch (serialNum) {
case 1:
Serial1.write(serialBytes, numSerialBytes);
Serial1.flush();
break;
default:
WiredSerial.write(serialBytes, numSerialBytes);
WiredSerial.flush();
}
return;
}
if ((val >= 0x40) && (val <= 0x5F)) { //WREG (Write Register) command
for (int i = 0; i < 5; ++i) if (Serialavailable(serialNum) < 1) delay(1);
if(Serialavailable(serialNum) < 1) return;
unsigned char numSerialBytes = Serialread(serialNum)+1;
for (int i = 0; i < 5; ++i) if (Serialavailable(serialNum) < numSerialBytes) delay(1);
if(Serialavailable(serialNum) < numSerialBytes) return;
unsigned char serialBytes[numSerialBytes];
for (int i = 0; i < numSerialBytes; ++i) serialBytes[i] = Serialread(serialNum);
digitalWrite(IPIN_CS, LOW);
SPI.transfer(val);
SPI.transfer(numSerialBytes-1); // number of registers to be written – 1
for (int i = 0; i < numSerialBytes; ++i) {
SPI.transfer(serialBytes[i]);
delayMicroseconds(1);
}
digitalWrite(IPIN_CS, HIGH);
}//if WREG
}

To view the data I am using the following code developed in python:

import serial

import numpy

import time

import sys, time, datetime, base64

canais=8

shift=0

tempo=0.1

total=numpy.zeros((canais, 1),dtype=long)

resultados=numpy.zeros((canais, 1),dtype=long)

#############################################

f = open('C:\pythonDados/workfile.txt', 'w')

ser = serial.Serial(port='COM106',baudrate=115200, timeout=2)

print("using device: %s" % ser.portstr)

print "configurando"

ser.write("\x11")

## WREG

##ser.write("\x41\x03\x1E\x90\xD0\xE8")

##ser.write("\x45\x07\x00\x00\x00\x00\x01\x01\x01\x01")

##ser.write("\x55\x00\x20")

## end WREG

## RREG

##ser.write("\x20\x19")#

##print "{0:b}".format(int((bin(ord(ser.read()))),2))

## end RREG

print "config"

ser.write("\x10")

print "feito"

while True:

dadosN=ser.read()

if ( int((bin(ord(dadosN))),2)&0b11110000)==0b11000000:

for i in range(0, canais):

resul=0

resul=int((bin(ord(ser.read()))),2)

resul=resul<<8|int((bin(ord(ser.read()))),2)

resultados[i,0]=resul

## f.seek(f.tell())

## f.write(str(bin(resul)))

## f.write('\n')

## print bin(resul)

total = numpy.concatenate([total,resultados], axis=1)

print total[0:1,len(total[0])-1]

#else:

#print "Falhou"

f.seek(f.tell())

f.write(str(total[0:canais,len(total[0])-1]))

f.write('\n')

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ADS1299 EVM Board single-ended measurement set up