ADS1298 with Arduino / not working

Hi,

I'm doing a research project about bioamplifiers and chose the ADS1298.

As a first step, I made a breakout board to access the pins and connected them to an Arduino, a breadboard and the development board as a power supply, but I'm not able read the chip's ID.
I use the Arduino for the SPI communication and as a power supply for the development board, which I use again in order to provide a biopolar supply for the chip on the breakout board.
I also installed the VCAPs. I tested my Arduino code with the development board and it works.

There is a schematic, a picture of the setup and the Arduino code attached. 

Is there something wrong with the wiring? Or could it be, that the chip is broken?

Thanks for any help

Dominik

#include <SPI.h>

void setup(){
  pinMode(4, OUTPUT);
  SPI.begin();
  SPI.setBitOrder(MSBFIRST);
  SPI.setDataMode(SPI_MODE1);
  adc_send_command(0x11);
  delay(500);
}

void loop()
{
  delay(500);
  Serial.begin(115200);
  int ID = 1;
  digitalWrite(4, LOW);
  SPI.transfer(0x20);
  delayMicroseconds(5);
  SPI.transfer(0);
  delayMicroseconds(5);
  ID = SPI.transfer(0);
  delayMicroseconds(1);
  digitalWrite(4, HIGH);
  Serial.println(ID);
}

void adc_send_command(int cmd)
{
  digitalWrite(4, LOW);
  SPI.transfer(cmd);
  delayMicroseconds(1);
  digitalWrite(4, HIGH);
}