Forum: µC & Digital Electronics STM32 & ADC AD7699: fading SPI MISO level

Author: Jan Bolting (Guest)
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Hey guys,

I'm facing a problem working with an STM32F103RET6 and an ADC AD7699
I thought maybe some of you might have similar experiences and could 
give me a hint. As you can see in the pictures, the signal level of the 
AD7699's SDO (SerialDataOut) pin doesn't drop straight to LOW during the 
last falling edge -though it does looking at the edges before, so I 
suppose it's not an electric issue - but slowly fades to LOW.
Any idea?

best regards

Author: soundso (Guest)
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looks like the sdo pin is going tristate (high impedance) at the end of 
the transmission. if so it is a electrical problem.

use a pulldown or pullup resistor on the line for a defined voltage 
level ...


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