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ADS1299: ADS1299 output has error.

Part Number: ADS1299

Hi,

I test ADS1299EVM connect to stm32 MCU.

In my case, the output data has two error.

First, output data has trend(negative gradient).

Second, Output data contaminated by digital signals.

I attach my output data file. Sampling rate is 250Hz.

Setting of Register is below.

ADS1299_Write(REG_CONFIG1, 0x96); 
ADS1299_Write(REG_CONFIG2, 0xC0);
ADS1299_Write(REG_CONFIG3, 0xFC);

ADS1299_Write(REG_CONFIG2, 0xC0);
ADS1299_Write (REG_CH1SET, 0x60);
ADS1299_Write (REG_CH2SET, 0xE0);
ADS1299_Write (REG_CH3SET, 0xE0);
ADS1299_Write (REG_CH4SET, 0xE0);
ADS1299_Write (REG_CH5SET, 0xE0);
ADS1299_Write (REG_CH6SET, 0xE0);
ADS1299_Write (REG_CH7SET, 0xE0);
ADS1299_Write (REG_CH8SET, 0xE0);

ADS1299_Write (REG_LOFF, 0x00); 
ADS1299_Write(REG_CONFIG4, 0x02); 
ADS1299_Write (REG_LOFF_SENSP, 0xFF);
ADS1299_Write (REG_LOFF_SENSN, 0xFF);
ADS1299_Write (REG_LOFF_FLIP, 0x01);

ADS1299_Write (REG_RLD_SENSP, 0x06); 
ADS1299_Write (REG_RLD_SENSN, 0x02); 

The internal test signal operate well.

Do you know about this error??

ads1299_output_error1.txt

  • Hello Sangkyu,

    Thanks for your post.

    What is the applied input signal to Channel 1 during your measurement? Can you provide more details about the input to IN1P and IN1N?

    I looked at the raw data output that you shared. Is this the raw output data from the ADC in decimal, or did you do some processing already? If I convert this data to voltage, assuming a 4.5-V reference, the output signal ranges from ~290mV to ~140mV, about 150mV difference. Does this voltage eventually settle if you leave your system running long enough?

    Regarding the "digital interference," it is difficult to know for sure what is going on. Usually, the first thing I would verify is if you are correctly converting the binary data into decimal using the binary two's complement format. However, the difference between two samples appears to be more complicated that this. Sample #17977 = 458,471 (0x06FEE7) and sample #17978 = 393,583 (0x06016F). I checked a couple other places and I do not see a direct correlation between the data.

    The register settings also look ok. Are there other things in your system that occur when you see the interference spikes?

    Best Regards,