adc120

[imnavajas]

We need to use the ADC chip ADC120 within our design, unfortunately the readout process that we perform only outputs channel IN0 data as output, regardless what we set in ADD2, ADD1 and ADD0 bits. I am not sure how to change the channel, but following the datasheet the SPI waveforms looks ok.

We came from a design where the TI ADC128s102 (pin to pin and SPI waveform compatible with ADC120) was the selected part, and appliying the same program the channel selected is read without any problem.

Please find attached the oscilloscope screenshot.

Thanks in advance.

​

[HaJes]

I am facing the same problem with the ADC120 evaluation board (STEVAL-AKI001V1). Have you been able to solve the problem?

Thanks, HaJes

[HaJes]

Meanwhile, I have been able to solve the problem. The hint is given in the application note AN5454 which reads as follows:

"The user attention is drawn to the fact that the data sampled at T0 time is outputted at T0+16SCLK on the DOUT bus. Another important point is that the device measures the channel 0 just after the CSn has been set low".

This means when reading just one channel that is different from 0, one needs to read 2x16 bit to get the result, which I wasn't aware of. I suggest adding the statement from the application note to the other documents (ADC120, RHFAD128, STEVAL-AKI001V1 and UM2691) to remove misunderstandings.

Thanks, Harald

[Peter BENSCH]

Thanks, @HaJes​, for the suggestion which we will try to accommodate in the documentation.

Regards

/Peter

[Jiri HLADIK]

Hello,

There is always channel 0 sampled after the chip enable by CS pin. After that you program channel to be sampled and next reading is done on that channel.

Chip is almost completely disabled without CS so it doesn't remember previous setup.

The input voltage is being tracked right after first SCK pulse but in that time the ADC channel is not programmed yet. So channel 0 is sampled by default at first reading after chip enable and during that time you program channel for next reading. 

Best regards

Jiri

[aksoy_otomasyon]

Hello Jiri HLADIK,

  I am trying to get other ch, but its fail. I read only first ch. 
Please in there any basic code can you share. 
Thank you.