Hi there,

for a project I want to sample an input signal with an ADC and send the 
digitized values via SPI to a microcontroller for further 
postprocessing.

My measurement configuration consits of a waveform generator that is 
connected to an single-to-differential circuit (DC2622A from Linear 
Technologies). The two differential signals are directly connected to an 
ADC eval board (EEVAL-AD4001-FMCZ) from Analog Devices. In the later 
course I want to connect the ADC directly with a microcontroller from ST 
(STM32F767ZI) via SPI. But for test purposes and to see if the hardware 
setup is correctly, but for now I am using the SDP-H1 Evaluation Board, 
which is recommended from Analog Devices for the ADC.

My problem is, that an input signal like a sinussignal with 2 volt 
peak-to-peak voltage occurs at the the testpoints IN+ and IN- as 
expected (two sinussignals with one signal phase-shifted by 180 
degrees). Nevertheless, if I run the evaluation software there are two 
problems. On the one hand I am expecting a sinussignal at the waveform 
tab, but there is nothing but a straight line at 0 volt and a short peak 
to -5 volt. And on the other hand, I am always getting an overvoltage 
indicator if i read the status bits. This only dissappears if i set all 
the other status bits like High-Z, Span Compression and Turbo mode, 
which does not make sence to me. Does anybody have an advice or know 
where my mistake is?

Can we get a Scope screenshot of the in+ and in- pins  in reference to 
the ADC gnd? They both shouldn't be negative

Rtz wrote:
> Can we get a Scope screenshot of the in+ and in- pins  in
> reference to
> the ADC gnd? They both shouldn't be negative

Oh sorry, I forgot that. Yes of course. Whereas the Channel 1 (red) is 
IN+ and Channel 2 (yellow) IN-.