ADS8688EVM-PDK: SPI Communication - pin ⁓RST/⁓PD - DAISY - ⁓REFSEL and others pins

Thank you so much Dale Li, I have some questions about things i didn' t understand

AVDD Supply

I read this on the datasheet:

<<Do not open jumper J17 if the ADS8688EVM must be powered only from the SDCC controller card and an external 5-V supply is not provided on J32.>>

So If I provide 5V to pin2 of J32 do I have to open J17?

Front-end amplifiers(U4)

When you refer to front-end amplifers(U4) do you refer to those "parts" which are connected to A0+ A1+ A2+ A3+ A4+?

I mean, when i use AVDD and DVDD can' t I use these "parts"?

I mean, I simply understood this:

When I use AVDD and DVDD:

- I can convert only signal coming from A5 A6 A7;

- For example: If I want to convert a signal coming from A0+ I need to open J25 and close J8 between pin 2 and 3. "Basically same" for other pins;

DAISY REFSEL & RST/PD

Thank you i didn' t notice that the RST/PD was shorted to DVDD. But now i have a doubt, i noticed that DAISY and REFSEL are shorted by resistors R15 and R18 to DVDD too. So If i short to GND DAISY and REFSEL they are connected to DVDD too. Or am i wrong?

USING LOGIC CONVERTERS FOR INPUT AND OUTPUT

My MCU has digital output and input between 0 and 5V, so I need to use some 3 logic converter from 5v to 3.3V( for SCLK SDI and CD) and 1 from 3.3 to 5V(SDO). But could these produce some problem for the performance of the ADC? In reality for the moment i need only to see the ADS works :)

Ok i get it. So, in each case i can use A0 A1 A2 A3 through front-end amplifiers, but if want to use them with HVDD and HVSS i need to open j17. In that case i have to be capable to provide at least (200mA or 500mA?) form j32. But in that case do I have to use even an external reference as the input signal is amplified? And what about DVDD in this case?

Returning to my configuration (internal reference, only one ADC etc...) i had some troubles. I connected the channel A6 to 3.3V but I don' t see nothing coming from the MISO, only LOW signal. I don' t know if there something wrong with the code but if it is possible, could you check the connection I made are correct?

-DAISY, grounded trough J2;

-REFSEL, grounded trough J4;

-RST/PD, i didn' t "get" this signal from anywhere;

-AVDD, i provide 5V trough pin 2 of j32;

-DVDD, I provide 5V trough pin 2 j33;

-GND,  I shorted it to my MCU ground trough pin1 of j32;

-A6+, I connected it to a 3.3V signal.

I decided not to use the wires that I soldered/welded to pin GND, AVDD, DVDD.

I didn't detach Wires soldered to these pins but I ensured that they didn' t touch anything during data capture. However I think i will detach them in case previous connection are fine.

Moreover I decided not to use logic converters as I provide 5v to DVDD.

I will attach another raw schematic of connections I made. I forgot to say that I have default jumper settings.

I said that because as the input signal is amplified by buffers U4 and U5 it could exceed the internal voltage reference (4V), and the ADC would not be able to make a right conversion. Or am I wrong?

Sorry Dale Li but I didn' t understand some things:

1. Where can I find pins 9/30 and Pin 34? Moreover I didn' t undertand what you mean for:

"Have you checked if AVDD and DVDD are correct on pin....".     Was you asking me if i the voltage on these pin is correct?

2.Well, I dont' know where I can get REFCAP signal. And what voltage level do i have to expect from REFCAP and REFIO?(I suppose 4V from REFIO but i am not sure). Moreover should I have to short them(REFIO and REFCAP) to anywhere or isn' t it necessary? I ask to you this because i didn' t use them.

sorry again Dale

edit:

1. sorry Dale, but when you refer to pin 9/30 and pin 34 do you refer to those of only the ADS8688 (not EVM)? If yes how could i check if AVDD and DVDD are correct on these pin? And again, what does it mean doing this thing(checking if AVDD and DVDD are correct on these pin)?

Thank you Dale Li

2. This is my first time I work with these parts, so I didn' t think I could do it(not sure if I could make damages). Yes i will use a multimeter;

4. Sorry Dale, but the picture you send is for using an External Reference? I want to use an internal reference. However you right as with an internal reference they "contain" an output signal;

6. Below the code

//include SPI library
#include<SPI.h> 
//Slave Select Pin. I will set it LOW to start communication and set HIGH to end it.
const int ss_pin=10;  // contain the pin number of Arduino
byte address_1; //First 8MSBit of address of channel
byte address_2; //Last 8LSBit of address of channel
byte voltage[2]; //It will contain the 16bit coming from the SDO of ADC
//it is a contator to count how many measuremnt I did.
int c=0;


void setup() // this code will run a time
{
  Serial.begin(9600);//settings for serial communication with PC
  pinMode(ss_pin,OUTPUT); //setting pin ss_pin as output. I need to set as output only it
  digitalWrite(ss_pin,HIGH); //Send an High signal to ss_pin
  
  Serial.println("Begin for 4 seconds"); //print message
  delay(4000);//wait 4 seconds

  //This Arduino has a 16Mhz frequency
  //setting for SPI Communication between Arduino and ADS
  SPI.beginTransaction(SPISettings(16000000, MSBFIRST, SPI_MODE1));
  address_1=B11011000;  //I want to use MAN_MODE by selecting channel A6
  address_2=B00000000;  //so i will set the bit from the most significant
  
  digitalWrite(ss_pin, LOW); //Set the slave select pin LOW. Start Communication
  delayMicroseconds(2);//wait 2 microseconds
  //I transfer 16 bit rapresenting the channel
  //SPI.transfer transfer 8 bit trough the SDI and return 8 bit from the SDO during only 8 clock cycles
  SPI.transfer(address_1); //first 8 bit
  SPI.transfer(address_2); //last 8 bit
  delayMicroseconds(2);
  voltage[0]=SPI.transfer(0); // I will get the first 8 bit from SDO
  voltage[1]=SPI.transfer(0); // I will get the last 8 bit
  delayMicroseconds(2);
  digitalWrite(ss_pin,HIGH);  //Set the slave select pin HIGH. End Communication
  
}

void loop() //This code will run more than one time
{

  //Same
  digitalWrite(ss_pin, LOW);
  delayMicroseconds(2);
  //By sending all 0 to SDI i decide to continue make measuramente on same channel(A6)
  SPI.transfer(0); 
  SPI.transfer(0);
  delayMicroseconds(2);
  voltage[0]=SPI.transfer(0);
  voltage[1]=SPI.transfer(0);
  delayMicroseconds(2);
  digitalWrite(ss_pin,HIGH);

  
  Serial.println();
  Serial.println(voltage[0]);
  Serial.println(voltage[1]);
  while (c>100) // For the moment i want to make only 100 
  {
    Serial.println("END");
    delay(1000);
  }
  c=c+1;
  delay(1000);
}