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ADS1298 stops to generate DRDY signals
Part Number: ADS1298R
I am having problem getting data out of my ADS1298, after configuring it in RDATAC mode. All my SPI routines are verified for reading and writing registers.
I have carried out many conditions to single out the problem.
- When I activate start pin and send the START command but dont read data from the device, DRDY signal is generated.. no problems. But as soon as i start reading from it, DRDY stops generating, pulls up to HIGH (5V) state.
- I have even tried to run it in RDATA (single shot) mode inside infinite loop, but I get the same result. DRDY doesnt generate! please help..
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In reply to Tom Hendrick:
ADS1298-breakout.schHere I have attached the schematic file of the board.
I have ensured that my SCLK is fast enough to not mess up the DRDY timing, DRDY is 500SPS and SCLK is fast enough to comfortably read 27 bytes of data from the ADS.
ADS_WREG(ADS1298_CONFIG1_REG, 0x06); //Data Rate = Fmod/1024, Low Power Mode
ADS_WREG(ADS1298_CONFIG2_REG, 0x10); //Test signals are generated internally
ADS_WREG(ADS1298_CONFIG3_REG, 0xD4); //PD_REFBUF enable, VREFP is set to 2.4V, RLD_REF is set, RLD_REF is fed externally, RLD_BUF enabled, RLD_sense is off, RLD is connected
ADS_WREG(ADS1298_LOFF_REG, 0x02); //Do not use
ADS_WREG(ADS1298_CH1SET_REG, 0x50); //Gain = 8, Normal electrode input
ADS_WREG(ADS1298_CH5SET_REG, 0x55); //Gain = 8, Test signals
ADS_WREG(ADS1298_CH7SET_REG, 0x65); //Gain = 12, Test signals
ADS_WREG(ADS1298_GPIO_REG, 0x00); //GPIO OUTPUT
ADS_WREG(ADS1298_RESP_REG, 0XF0); // Respiration phase = 90, Internal Respiration of with user generated signals
ADS_WREG(ADS1298_CONFIG4_REG, 0X00); //64 kHz modulation clock
I am sorry, I dont have any images of waveforms!
One more detail that i think may be of interest is that - When i initialize the ADS, VCAP1 capacitor charges to about 1.019V no matter how much delay I set in the code. Only when I start reading and DRDY halts, VCAP1 voltage exceeds 1.1V (as i observed in the datasheet). Can this be the issue?
In reply to NINAD GANDHI:
Alex SmithApplications Engineer | Precision Delta-Sigma Converters
Check out our helpful resources: Common Questions for TI's ADS129x Family of Bio-Potential ADCs
TI Precision Data Converters | TI Precision Labs - ADCs | Analog Engineer's Calculator | Data Converters Learning Center | Selection Guide
In reply to Alexander Smith:
Sorry about the schematic. I have uploaded the schematic pdf file!
More development on my problem is that when I changed some capacitors (prescribed in the datasheet) DRDY pin does toggle, data does come. But the problem still intermittently persists.
So i am guessing that it is a problem with the interfacing Capacitors and Resistors. can you please point out if there are some Caps (or Res) whose prescribed values have to be stringently be followed?
Answering your question, the voltage at VCAP1 pin reaches about 1.161V
Please inform me if the pdf file still doesnt open, and i am attaching the schematic again.7142.ADS1298-breakout.sch
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