ADS131E08 CONFIG2 register read-back issue.

mohamad mahmoud

I configure the chip to run at 1 KSPS, and to use 4 volt external reference. I program the configuration registers as following:

CONFIG1=0x96 for 24-bit resolution and speed 1KSPS

CONFIG2=0xE0 the RESET VALUE

CONFIG3=0x40 for external reference.

the issue when I'm reading back the registers value I'm finding that the CONFIG2=0xE1 which should be 0xE0 according to the datasheet reset value. any help in this issue please? does it affect the performance of the ADC?

another issue is that I connected the Differential analog negative input 1 to the ground, but i see on the scope that the voltage value dropped on the pin is 1.8 volt? any explanation?

over 9 years ago

0 Brian Pisani over 9 years ago

TI__Mastermind 38745 points

Hey Mohamad,

The CONFIG2 register should definitely read 0xE0 if it is not changed from startup. Have you verified this is what is actually coming back on the DOUT line with an oscilloscope?

I'm not sure what you mean with the second question. If it is connected to ground, you should read 0V when it is probed. Otherwise it is not connected to ground. Is this how you are measuring or are you taking a conversion result and measuring 1.8 V?

Regards,
Brian Pisani

0 mohamad mahmoud over 9 years ago in reply to Brian Pisani

Prodigy 85 points

hi,
thanks for the answer, for the CONFIG2 register, i tried to read the value after startup without changing it, and I tried to write 0xE0 and read-back, but always it is reading back 0xE0. all the other registers including the data-out and the fault status are reading correctly. I'm pretty sure it is not a communication error, but even i'll try to monitor the output with the scope.

for the second question, as you said, the negative input channel is connected to ground, but i'm measuring 1.8 volt on it.!

0 Brian Pisani over 9 years ago in reply to mohamad mahmoud

TI__Mastermind 38745 points

Hey Mohamad,

If you write 0xE0 and you still read back 0xE1, then my suspicion is that there is a SPI communication problem.

If you are probing it and it is not equal to ground, then it must not be connected to ground. Try using the "short detector" on a multi-meter to see if there is a short between ground and the negative input.

Brian

0 mohamad mahmoud over 9 years ago in reply to Brian Pisani

Prodigy 85 points

hi,
you are write, I checked with the hardware designer, the negative input is floating, is not connected to ground, for the CONFIG2 register, I'm in progress to monitor the Dout on the scope.
I'll update you.

thanks a lot.

0 mohamad mahmoud over 9 years ago in reply to mohamad mahmoud

Prodigy 85 points

hi, I'm sorry I made a mistake, the issue is with coinfig3 register, the readback value is 0x41 while it should be 0x40.

0 mohamad mahmoud over 9 years ago in reply to mohamad mahmoud

Prodigy 85 points

all the other registers are being written and read correctly.

0 Brian Pisani over 9 years ago in reply to mohamad mahmoud

TI__Mastermind 38745 points

That bit is a "don't care". There is nothing to worry about it it reads back as 1.

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ADS131E08 CONFIG2 register read-back issue.