ADS1294 test signal configuration

Hi,

I am using ADS1294 with STM32 master.
I have followed the initialization sequence in figure 77 from the data sheet, but I am still not able to receive the test signal correctly.
The SPI communication works well - I am able to read and write to the register without problems.

Here is my register configuration:
CONFIG1 = 0x86
CONFIG2 = 0x10
CONFIG3 = 0xC0
CH1SET = 0x5
CH2SET = 0x5
CH3SET = 0x5
CH4SET = 0x5

and my configuration code:

void ads_init(void) {
uint8_t ads_reg[30];
memset(&ads_reg[0], 0xAB, sizeof(ads_reg));//dummy Value

//init GPIOs, SPI and interrupts
ads_low_level_init();
nDRDY_init();

//init the double buffer
doubleBuff.active_buff = doubleBuff.adc_buff_A;
doubleBuff.not_active_buff = doubleBuff.adc_buff_B;
doubleBuff.counter = 0;
doubleBuff.buff_voll = false;
memset(doubleBuff.adc_buff_A, 0, sizeof(doubleBuff.adc_buff_A));
memset(doubleBuff.adc_buff_B, 0, sizeof(doubleBuff.adc_buff_B));

//activate ads1294
ADS_nPWDN_HIGH;
ADS_nRESET_HIGH;
delay_ms(2);

//perform reset
ADS_nRESET_LOW;
delay_ms(2);

ADS_nRESET_HIGH;


// Device Wakes Up in RDATAC Mode, so Send SDATAC Command so Registers can be Written
ads_send_command(ADS_SDATAC);

// use internal reference
ads_reg[0] = 0b11000000;
ads_write_to_register(CONFIG3, 1, &ads_reg[0]);

//set to high resolution mode f_DRDY=500Hz
ads_reg[0] = 0b10000110; //CONFIG1 500SPS
//set to high resolution mode f_DRDY=8kHz
//ads_reg[0] = 0b10000010; //CONFIG1 8kSPS
ads_write_to_register(CONFIG1, 1, &ads_reg[0]);
ads_reg[0] = 0;
ads_write_to_register(CONFIG2, 1, &ads_reg[0]);

//set all channel to input short
ads_reg[0] = 0x1;
ads_reg[1] = 0x1;
ads_reg[2] = 0x1;
ads_reg[3] = 0x1;
ads_write_to_register(CH1SET, 4, &ads_reg[0]);

ADS_START_HIGH; //after this line nDRDY starts toggle with f=500KHz
ads_send_command(ADS_RDATAC);

while (doubleBuff.buff_voll == true) {
//TODO calc offset
doubleBuff.buff_voll = false;
}

ads_send_command(ADS_SDATAC);

ads_reg[0] = 0x10;
ads_write_to_register(CONFIG2, 1, &ads_reg[0]);

//set all channel to test signal
ads_reg[0] = 0x05;
ads_reg[1] = 0x05;
ads_reg[2] = 0x05;
ads_reg[3] = 0x05;
ads_write_to_register(CH1SET, 4, &ads_reg[0]);


//this two lines of code are used only for debug purposes in order to ensure that the registers are written correctly
memset(&ads_reg[0], 0xAB, sizeof(ads_reg));//some dummy value
ads_read_from_register(CONFIG1, 8,&ads_reg[0]);


//put device into RDATAC mode
ads_send_command(ADS_RDATAC);


}

Best regards,
Stefan