ADS8688A: Can't read ADC values from ADS8688

Beşir Demir

Prodigy 20 points

Part Number: ADS8688A
Other Parts Discussed in Thread: ADS8688,

Hi,

I am trying to read ADS8688 ADC inputs, but I couldn't read. Please could you review and give feedback.

Schematic is below.

I try arduino code shared in https://github.com/siteswapjuggler/ADS8688a

Then I see always constant voltage in each channel, on the other hand there is no voltage for inputs, ın channel 0 there is 1 V is. But it see all channel with 5.07V

Also I change the range to R6 in Arduino code.

Also I want to strudy this circuit with raspberry pi 4 , if there is any application example could you share.

Thanks, Regards.

over 3 years ago

0 Dale Li over 3 years ago

TI__Mastermind 45955 points

Hi Besir,

Your schematic looks good. You may consider to send a reset signal the device through /RST pin if it is possible for you. Regarding the issue, I would suggest to start the test without programming the device. The default channel on the ADS8688A is AIN_0, so you can convert the channel AIN_0 by sending SCLK clocks and /CS to the ADC according to the timing of Figure 1 in the data sheet. Please share a few oscilloscope plots of the /CS, SCLK, SDI and SDO to verify the timing on the interface. Also, please ensure the oscilloscope probes are placed close to the pins of the ADS8688A device.

We do not have an example code for a specific microcontroller. Below is a C code example, please check Source Files:

http://www.ti.com/tool/ADS8688SW-LINUX

Thanks and best regards,

Dale

0 Beşir Demir over 3 years ago in reply to Dale Li

Prodigy 20 points

Thanks for your response,

However I set REFSEL to GND over 47k I couldn't see the internal reference voltage which must be 4.096V at REFIO pin. Is it a normal state? Do we need to set any register?

0 Beşir Demir over 3 years ago in reply to Beşir Demir

Prodigy 20 points

I check again and I see it was soldiring problem.

Thanks and best regards

0 Dale Li over 3 years ago in reply to Beşir Demir

TI__Mastermind 45955 points

Hi Besir,

I'm sorry for missing your post. Thanks for your update. Let me know if you need any further support.

Best regards,

Dale

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ADS8688A: Can't read ADC values from ADS8688