ads1299 sclk

Hi,Brian,is that mean the LSPCLK must be set less than SYSCLKOUT/8(18MHz) when i use tms320f28335?

hi,brian,my logic high level is3.3v.i have another qusetioin ,what is the difference between  baud rate and sclk?

does the sclk come from the baud rate generator? i have set the baud rate LSPCLK/8 ,is that mean the sclk is LSPCLK/8 too?

Hi Sonia,

If your logic level is 3.3 V, then the 18 MHz serial clock should be fine.

In general, the difference between baud and bit rate is baud represents the number of symbols which can be represented per second and the bit rate is how many bits can be sent per second. In the case of a single communication line (per direction) as is the case with SPI, the number of bits which are used to transmit each symbol is just 1 since a symbol on one communication line can either be a 1 or a 0. In this case the baud and bit rates are the same.

For the microcontroller you are using, I believe LSPCLK is the clock which comes to the SPI peripheral from the main clock generator in the core which is then divided by value in the SPIBRR generator to produce the SCLK. So yes, your interpretation is correct. If you are still unsure, look at the SCLK that gets generated off the processor using an oscilloscope and make sure the frequency is what you expect.

Regards,

Brian

Hi，Brian

thank you for your  help.  a 1Vp single ended signal that was centered at 2.5V with respect to ground  is that mean it swing from 3.5v to2.5v  and 2.5 v to1.5v?

 if i want to measure a signal that generated by the signal generator, i doubt if i can connect the signal to the AINP  and the signal ground to the AINN?

regards

sonia

Hi Brian

i got it ,thank you. now i'm going to measure EEG,but it didn't mention what kind of EEG electrode should be applied to the ads1299EEGFE ,could you give me some advice?

regards

sonia

Hi Brian

i'll take the safe into consideration ,thank you for your advice .

best wishes

Hi Brian,

sorry to trouble you,but i got a proble when i tried to measure the EMG.I had measure the test signl on chip , when i measured the EMG  in Channel 1, i can't get any signal .

I place the positive electrode and the BIAS_ELEC on the same arm and  short  the 3,4 of JP25,so the mid-supply can be introduced to the negative input through SRB1,and to my body through biad electrode .

But i find Channel 1 is always 0,and Channel 8 always have signal even when i power it down. this is my code, could you give me some advice?

WREG(ADS1299_REG_CONFIG3,1,0xe0);       //enable internal reference
   WREG(ADS1299_REG_CH1SET,1,0x20);        // gain=4,normal electrode input
   WREG(ADS1299_REG_MISC1 ,1,0x20);        //enable SRB1
   WREG(ADS1299_REG_CH2SET ,1,0x90);       //power down the rest channel
   WREG(ADS1299_REG_CH3SET ,1,0x90);
   WREG(ADS1299_REG_CH4SET ,1,0x90);
   WREG(ADS1299_REG_CH5SET ,1,0x90);
   WREG(ADS1299_REG_CH6SET ,1,0x90);
   WREG(ADS1299_REG_CH7SET ,1,0x90);
   WREG(ADS1299_REG_CH8SET ,1,0x90);

Hi Brian,

i have shorted 5 ,6 of JP25 to introduce the mid supply to the negative input ,and connect the bias eletrode to JP17 to introduce the BIAS_DRV to my arm ,but the signal in channel 1 is still 0,even in differential input mode that i put the negative electrode and the positive electrode on my arm.

And i can measure the test signal in channel 1. I'm confused about it. 

WREG(ADS1299_REG_CONFIG3,1,0xe0); //
WREG(ADS1299_REG_CONFIG2,1,0xd0); //internal test signal amplitude=5/2.4mv fre=fCLK/2
WREG(ADS1299_REG_CH1SET,1,0x25);
//WREG(ADS1299_REG_MISC1 ,1,0x20); //enable SRB1
//WREG(ADS1299_REG_BIASSENSP ,1,0x01);
//WREG(ADS1299_REG_BIASSENSN ,1,0x01);
WREG(ADS1299_REG_CH2SET ,1,0x90); //power down the rest channel
WREG(ADS1299_REG_CH3SET ,1,0x90);
WREG(ADS1299_REG_CH4SET ,1,0x90);
WREG(ADS1299_REG_CH5SET ,1,0x90);
WREG(ADS1299_REG_CH6SET ,1,0x90);
WREG(ADS1299_REG_CH7SET ,1,0x90);
WREG(ADS1299_REG_CH8SET ,1,0x90);

regards

sonia

Hi Brian,

the signal doesn't  look  like noise ,it is always 0.when i set channel 1 in normal input mode, i put the positive electrode and the negative electrode on my arms ,but the signal is 0,without a fluctuation.

i don't know why? shoud i connect my arm to the ground of the ads1299?

regars

sonia

Hi Brian,

i the signal of channel 1 doesn't varies when i put a an electrode on my hand ,i set the negative inpu mid-supply,this is the wave and my code,is there any bug in my code ?

 RESET();      //reset ads1299
   DELAY_US(20);
   SDATAC(); //stop RDATAC model
   DELAY_US(8);
   WREG(ADS1299_REG_CONFIG3,1,0xe0);       //
   //WREG(ADS1299_REG_CONFIG2,1,0xd0);       //internal test signal amplitude=5/2.4mv fre=fCLK/2
   WREG(ADS1299_REG_CH1SET,1,0x20);
   WREG(ADS1299_REG_MISC1 ,1,0x20);        //enable SRB1
   //WREG(ADS1299_REG_BIASSENSP ,1,0x01);
   //WREG(ADS1299_REG_BIASSENSN ,1,0x01);
   //WREG(ADS1299_REG_CH2SET ,1,0x90);       //power down the rest channel
   //WREG(ADS1299_REG_CH3SET ,1,0x25);
  // WREG(ADS1299_REG_CH4SET ,1,0x25);
   //WREG(ADS1299_REG_CH5SET ,1,0x25);
   //WREG(ADS1299_REG_CH6SET ,1,0x25);
   //WREG(ADS1299_REG_CH7SET ,1,0x25);
   //WREG(ADS1299_REG_CH8SET ,1,0x25);
   START();
while(1)
 { while(flag==1)
   {while(GpioDataRegs.GPCDAT.bit.GPIO71!=0);//DRDY is low
   RDATA();
   DELAY_US(200);
   for(i=0;i<27;i++)
    {spi_xmit(0x00);
     while(SpiaRegs.SPIFFRX.bit.RXFFST!=1);
     dat=SpiaRegs.SPIRXBUF;//read  data
     scia_xmit(dat);
     }
    }
 }

}

Hi Brian,

thank you for your advice,i found   something  wrong when receiving data,and i had fixed it .now i can measure signal in differential input mode,but the channel got a lot of noise like this when nothing introduced to the channel .

besides, i found  the voltage of  channel 1,2,5,6,7,8 are about 2.5 v   when i measure the supply in bipolar  .

Is that should be 0 when AVDD is 2.5v and AVSS is -2.5v ?

regars

sonia

Hi Brian,

The input pin is floating when i say it is not connect,and there is still so much noise when it is actively driven.

when i measre supply ,i set mux 011 in biopolar supply. is the noise  power line interference?

regars

sonic

Hi Brian,

now ,i wanna remove the interference with labview .is the sampling frequence of the filter coefficients should be set at 250,when the ads1299 DR is 250sps?

in the power spectrum of the interference array as follows ,the frequence of the interference is at 100 and 150 （  the Δf=fs/N，fs=250（DR=250SPS））.as

the power line interference is at 50hz in my country,is something wrong ?or the filter sampling frequence should not be set to 250,though the DR is 250sps,considering the transmitting time and delay ?

regars

sonia

Hi Brian

when i introduced a sinusoidal wave into channel 1 in differential mode, set  conifg3 at 0xe0, channel 1 at 0x20 in the register.

 the data  i got  is as the following picture.it  seems different from the sinusoidal wave,could you tell me why?

regars

sonic